From autopoiesis to neurophenomenology

This paper reviews in detail Francisco Varela's work on subjectivity and consciousness in the biological sciences. His original approach to this "hard problem" presents a subjectivity that is radically intertwined with its biological and physical roots. It must be understood within the framework of his theory of a concrete, embodied dynamics, grounded in his general theory of autonomous systems. Through concepts and paradigms such as biological autonomy, embodiment and neurophenomenology, the article explores the multiple levels of circular causality assumed by Varela to play a fundamental role in the emergence of human experience. The concept of biological autonomy provides the necessary and sufficient conditions for characterizing biological life and identity as an emergent and circular self-producing process. Embodiment provides a systemic and dynamical framework for understanding how a cognitive self--a mind--can arise in an organism in the midst of its operational cycles of internal regulation and ongoing sensorimotor coupling. Global subjective properties can emerge at different levels from the interactions of components and can reciprocally constrain local processes through an ongoing, recursive morphodynamics. Neurophenomenology is a supplementary step in the study of consciousness. Through a rigorous method, it advocates the careful examination of experience with first-person methodologies. It attempts to create heuristic mutual constraints between biophysical data and data produced by accounts of subjective experience. The aim is to explicitly ground the active and disciplined insight the subject has about his/her experience in a biophysical emergent process. Finally, we discuss Varela's essential contribution to our understanding of the generation of consciousness in the framework of what we call his "biophysics of being."


INTRODUCTION
In this paper we will review Francisco Varela's ideas about what is now often called the "hard problem" (Chalmers, 1996): the issue of the relationships between our subjective experience and our objective bio-physical embodiment.
Francisco Varela liked to introduce himself by saying: "I'm a biologist who has been interested in the biological roots of cognitive phenomena" (Varela, 1990).From this standpoint, he investigated the biological basis of subjectivity and conscious experience throughout his life as a researcher.He did so in a very original way, illuminating this fundamental issue with deep and fascinating insights.
In the last years of his life, he proposed a scientific research program, which he called neurophenomenology (Varela, 1996), that aimed to address the problem pragmatically.This program has already produced interesting results (Lutz et al, 2002) and is currently being conducted by colleagues from his French Brain Dynamics team, including the authors of this paper.With more than 180 published articles and 10 books (not to mention the many books he edited), Francisco's work extends into many scientific fields: cybernetics, neurophysiology, theoretical biology, mathematics, immunology, epistemology, neuropathology (epileptology), brain imaging and brain dynamics.
Francisco Varela was a mentor to all of the present authors: one year after his premature death, this article serves both as homage and as an occasion to share one possible synthesis of his work with the scientific community.One of its goals is to disclose the coherence of his thinking throughout his career, situating his later and final views on the biology and phenomenology of consciousness within the framework of his general theory of a u t o n o m o u s s y s t e m s .T h i s t h e o r y , developed early on, is essential for a full understanding of what he meant by "embodied mind" (Varela et al, 1991;Thompson and Varela, 2001).
Although this article is presented as a synthesis, we have chosen to include a large corpus of quotes and references in order to provide the reader with concrete points of access to these abstract and complex ideas.We have used a system of notes so as not to interrupt the flow of the text.
T h e f r a m e w o r k s k e t c h e d h e r e i s necessarily partial in relation to the richness and multiplicity of Francisco Varela's thought, which includes not only reflections on theoretical biology, immunology, neuroscience, phenomenology and the epistemology of science, but also on ethics and spirituality, domains of profound personal commitment for him.
Finally, while the authors obviously agree on the views and material presented here, the interpretations and emphasis placed on different aspects of Francisco's work by each one of us clearly varies.Given the richness and diversity of his thought, we cannot claim to have exhausted all possible points of view in this synthesis; indeed, to attempt to do so would only limit the p o s s i b i l i t i e s o f o u r o w n p e r s o n a l explorations of his deeply insightful work.

The thematic landscape
Through more than thirty years of research Francisco searched for an account of cognition.Some periods of particular interest can be distinguished: the years from 1968 to 1986 were marked by his work both on the neurophysiology of vision and on cybernetics, first with Torsten Wiesel at Harvard and later with Humberto Maturana at the University of Chile, (reflections on brain organization can already be seen here); from 1986 to 1995 he was particularly interested in self-organization in immune networks; finally, from 1995 until his death in May 2001, he worked on brain dynamics, anticipation of epileptic seizures and neurophenomenology with his French brain d y n a m i c s g r o u p i n t h e C o g n i t i v e N e u r o s c i e n c e a n d B r a i n I m a g i n g Laboratory in Paris.
Yet this arbitrary division into historical periods should not mask the continuity of his thinking: as early as 1971 he devoted an article to the issue of self-consciousness (Varela, 1971) while in 1997 he was still writing about autopoiesis and autonomy (Thompson and Varela, 1999).
For Francisco, theory was a crucial complement to experimentation in scientific work.Almost two thirds of his articles, book chapters and reviews are theoretical: about a quarter are experimental papers, principally produced during the first and last periods of his career; the rest are methodological papers, mainly written during the last period of his life, in which Varela addressed large-scale synchronies and non-linear analysis of brainwaves, including works on seizure anticipation.
In the following paper, while many of the Francisco's views might appear to be very speculative, they are so in a heuristic way: we hope they will be received as the fundamental contribution we believe them to be.

Setting the stage: experience as explanandum
It is a major challenge for contemporary naturalistic science to explain the existence and functioning of consciousness on a subjective, experiential level as well as in terms of its putative causal efficiency ( P e t i t o t e t a l , 1 9 9 9 ) .T h e r e c e n t development of brain imaging techniques (such as fMRI, PET, MEEG/EEG) and progress made in signal analysis for characterising fast dynamical interactions (cf. Tootell et al, 1998;Lachaux et al, 1999;Friston, 2002), which allow the study of the human brain during cognitive tasks, have provided an essential experimental framework for research into consciousness.
C o m p u t a t i o n a l i s t , f u n c t i o n a l i s t o r neuroreductionist approaches generally lead to a paradoxical eliminativism, i.e. the elimination of consciousness as the domain of our subjective experience during the very process of explanation.No evidence about the relation between the objective and subjective realms can be provided if the initial explanandum itself (that which has to be explained), has been banished as a valid object of study!In the explanation, phenomenal properties of consciousness as such must appear (Varela, 1976;Varela, 1996;Roy et al, 1999).
Contrary to eliminativism, it is well known that Francisco's position was situated squarely in the context of what he saw as the irreducible nature of conscious experience.
As early as 1976 (Varela, 1976), he called for a science of the "sense of self," of "direct knowledge"1 .He sought a science of mind embodiment (Varela et al, 1991) that incorporates "experience," "being there" (Varela, 1999c), "sentience" and "the feeling of being alive" (Thompson and Varela, 2001).He addressed the need for a methodology to explore this realm, "an experiential neuroscience" (Varela, 1999b) at the concrete roots of the emergence of consciousness .Varela posed the problem as follows: "on the one hand we need to address our condition as bodily processes; on the other hand we are also an existence which is already there, a Dasein, constituted as an identity, and which cannot leap out and take a disembodied look at how it got to be there" (Varela, 1991).For Francisco, cognition always takes place in the context of "feeling consciousness and intuition" (Varela, 1976).
" E x p e r i e n c e " o r " p h e n o m e n a l experience" (Varela, 1996) is that part of our cognition that we access from a subjective point of view; it is the realm of consciousness."Mind," on the other hand, embraces the more general domain of cognition, which includes conscious and unconscious phenomena while always being rooted in a self.Indeed, our intuitive apprehension of mind shows it to be fundamentally related to subjectivity and consciousness: A mind is always someone's mind, my mind; thus, the issue of the mind cannot be seen to be independent from that of the self.In Francisco's words: "Here, by 'mind' I mean anything that has to do with mentality, with cognition and ultimately with experience" (Varela, 1999b).

The Nagel Effect
In Nagel's famous article, What is it like to be a bat?, to which Francisco often referred (1974) the author framed the issue by stating that "fundamentally an organism has conscious mental states if and only if there is something that it is like to be that organism -something it is like for the o r g a n i s m ." F o r N a g e l t h i s " e f f e c t " corresponds to the "subjective character of experience," which is related to a "point of view," constituting the "essence of the internal world."Pithily, he observes that "if mental processes are indeed physical processes, then there is something it is like, intrinsically, to undergo certain physical p r o c e s s e s ." W e w i l l r e f e r t o t h i s hypothetical mental effect of having physical processes as the Nagel Effect.
Within such a framework we must wonder, as Nagel suggests, what "objectivity" can tell us about subjective experience, how an objective process can have a subjective nature and, reciprocally, how subjective experience can have an objective nature.
A c c o r d i n g t o t h e p h y s i c s m o d e l , "objectivity" accounts for observable properties in the World, by describing them as spatial-temporal interactions between spatial-temporal elements defined as structures or dimensions in a state space with laws of evolution.Objectivity is the realm of the phenomenology of objects, processes, trajectories, force, field, attraction, repulsion, acceleration, mass, energy, etc.The crucial question is how such modes of description can provide us with deep insights about the "origin" of our subjective experience. 2ccording to Francisco, the search for the origin of this Nagel Effect of subjective experience must be grounded in the notion of a "radical embodiment," that is, in the concrete situated phenomenology of our coping as a biophysical system (Varela et al, 1991;Thompson and Varela, 2001).
Embodiment is a key, if complex, concept.This article will illuminate precisely what F r a n c i s c o m e a n t b y e m b o d i m e n t o r embodied mind.References to the notion of embodiment always include the notion of mind; in humans, it cannot be separated from either the notion of mind or that of self.In Francisco's view, embodiment is our departure point as living beings, a given that we must characterize, but also the explanans, i.e. the domain of explanation for a future science of being.Embodiment is fundamentally related to what he called the natural history of circularity (Varela, 1988a).Throughout this article the notion o f c i r c u l a r i t y a n d i t s p r e c i s e phenomenology will be omnipresent.
As will become apparent in the following pages, his theory of embodiment continuously moves between the pursuit of an operational, concrete description of biophysical processes and the choice of very abstract and general tools to build explanations or fill out insights (Varela, 1979).Yet these abstract or general concepts were always shaped to fit as closely as possible the model or nature of the system's mechanisms.Francisco studied the natural fact of embodiment simultaneously from the perspectives of a biologist, a cybernetician and a neuroscientist, often using tools and systemic descriptions based on non-linear mathematical physics3 .His approach motivated the reference to a biophysics of being4 in the title of this article.
At the same time, Francisco's conceptions are all grounded in a phenomenological approach to subjectivity as well as to the organism itself.In Francisco's theoretical developments,5 the embodiment of mindwhether approached from the first-or thirdperson point of view-always has the character of a descriptive phenomenology.
This paper is an attempt to highlight the logic that guided the greater part of Francisco's work, starting from his general principles of "living systems" as a necessary prelude to the understanding of human subjectivity.Our approach to Francisco's theory follows a 'constructivist' path: beginning with the theory of autopoiesis and autonomy, we move on to examine how Francisco frames embodiment theoretically, a n d e n d w i t h n e u r o p h e n o m e n o l o g y .Although our objective is not to look at the concepts historically, the order of this presentation coincides generally with the historical order of Francisco's conceptual developments.

AUTONOMOUS SYSTEM
Our point of departure as embodied beings is situated in a general framework that concerns all living systems: that of autonomy. 6In this section, we will present Francisco's thought on our fundamental organization as living beings, and the c o r r e s p o n d i n g t h e o r e t i c a l o b j e c t h e constructed: the autonomous system.

Life as a " bringing forth" of identity
" W h a t a r e t h e b i o l o g i c a l r o o t s o f i n d i v i d u a l i t y ?" ( V a r e l a , 1 9 8 7 ) T h e f u n d a m e n t a l f e a t u r e t h a t H u m b e r t o Maturana and Francisco identified in their search for what is common to all living beings (that which makes us recognize them as belonging to the same class despite their diversity), was the evidence of a unitary nature, a coherent wholeness, an autonomy that is "brought forth" by the system itself (Maturana and Varela, 1973;Varela et al, 1974;Maturana and Varela, 1980).There is a "capacity of living systems to maintain their identity in spite of the fluctuations which affect them" (Varela, 1979;Maturana and Varela, 1973;Varela et al, 1974).This identity is actively resistant to all the natural forces and tendencies, such as the increase of entropy, that tend to annihilate it.What is indeed fascinating about living beings is that they assert their identity from within, thus opening up the possibility of observing them as distinct units in their domain of operation.The living being is a process, that of "being autonomous" (Varela, 1977a).Therefore, it is not Reproduction or Evolution or any list of properties that primordially characterizes life, but rather individual organization that allows for autonomy (Varela, 1984a).For instance we can conceive of the existence of such an o r g a n i z a t i o n w i t h o u t a b i l i t y o f Reproduction and Evolution, but the reciprocal is not true.
As an autonomous individuality, a living system does indeed present itself to observers with "wholeness," as a "systemwhole," a "total, closed, complete, full, stable, self-contained system" (Varela, 1976).As a whole, it behaves as a dynamical system exhibiting continuous structural changes but with organizational invariance.This organizationally invariant process defines the system's identity (Varela, 1984a): "the domain of deformations that the system can be submitted to without losing its identity (i.e. and still maintain its o r g a n i z a t i o n ) i s t h e d o m a i n o f transformations where it exists as a unity" (Varela, 1979).
From a cybernetic perspective Francisco conceived this wholeness as the result of a co-dependency of parts in an ongoing process: "A whole is here a set of s i m u l t a n e o u s i n t e r a c t i o n s o f p a r t s (components, nodes, sub-systems) which exhibit stability as a totality.The parts are the carriers of particular interactions which we can chop out from the whole and consider their participation in various sequential processes that constitute the whole.The whole re-emerges when we see the resulting total stability (i.e. the fixed point of the limit process)" (Varela, 1976).Thus, it is more than a question of specific chemical components (carbon hydrates, proteins, lipids, nucleic acids, etc.), but is fundamentally one of "the relations which the components must satisfy in order to constitute a living system" (Varela, 1979).
Within this framework it must be noticed that Francisco's approach was radically m e c h a n i s t i c : " o u r a p p r o a c h w i l l b e mechanistic.We won't appeal to any forces or principles not belonging to the universe of physics [...] We adopt in fact the basic principles of the Cybernetics and the Theory of systems.What is just the essence of the modern mechanism.Living systems are 'machines'" (Varela, 1979).Thus, for Francisco, living beings were "mechanistic (dynamical) systems defined by their organization" (Varela, 1981).
Starting from these considerations, F r a n c i s c o a n d H u m b e r t o M a t u r a n a proposed a general but powerful biophysical mechanism, foundational to what Varela called the "bio-logic" (Varela, 1991).
Contrary to the usual way a machine functions, with a product that is different from the machine itself, in the case of living m a c h i n e s s e l f -p r o d u c t i o n i s t h e fundamental defining feature of the autonomy of the organism (Maturana and Varela, 1973).Thus, in the particular case of living organisms, the mechanism of autonomy was baptized autopoiesis or selfproduction: "An autopoietic system is organized (defined as a unity) as a network of processes of production (transformation and destruction) of components that produces the components that: 1) through their interactions and transformations continuously regenerate and realize the network of processes (relations) that produce them; and 2) constitute it (the machine) as a concrete unity in the space in w h i c h t h e y e x i s t b y s p e c i f y i n g t h e topological domain of its realization as such a network" (Varela, 1979).
In such a process (Fig 1) there is a mutual specification or definition of the internal, chemical transformations and of the physical boundaries (Varela, 1988b).Identity emerges and persists within the bounded system through a continuous circular or recurrent process.Specific organizational relations (like the ensemble of biochemical pathways of the cell and its membranes), bounding the metabolism and t h e p h y s i o l o g y o f t h e s y s t e m , a r e continuously regenerating through the internal production of their substratum components (cell organelles and structures, molecules controlling the metabolism) in FIGURE 1 -The autopoietic machine: a circular causality.The autopoietic organization is defined as a unit by a network of production of components (chemical reactions) which (i) participate recursively in the same network of production of components (chemical reactions) that produced them, and (ii) carry out the network of production as a unit in the space in which the components exist.
the correct functional, dynamical and spatial distribution.In other words, the system continuously produces itself through the production of its own components in the topological distribution that the ongoing global process constrains, and that the components require to maintain the relations that define them.Living systems "transform matter in themselves in such a way that their organization is the product of their operation" (Varela, 1979).
Within such a self-referential framework, the "origin of life" is conceived as the transition from a chemical environment to a self-produced identity (Dupuy and Varela, 1 9 9 1 ) .T h e m o s t p a r a d i g m a t i c c a s e exemplifying this mechanism is that of cell autonomy, but it applies to all living systems.This is valid also for superior organisms whose internal self-producing mechanism lies in integrated, recurrent, internal, metabolic and physiological relationships, with increasingly complex behaviors and functional dependencies.
As generative of living autonomous systems, autopoiesis appeared to Francisco as the common, specific feature, the uniqueness, of life: autopoiesis is "the mechanism which endows living systems with the property of being autonomous; autopoiesis is an explication of the autonomy of the living" (Varela, 1981).It is the biophysical origin of individuality: "It is autopoiesis which defines the cell as a unity endowed with an individuality" (Varela, 1979).Furthermore, autopoiesis is a generative concept: "We claim that the notion of autopoiesis is necessary and sufficient to define the organization of the living being" (Maturana and Varela, 1973).T o F r a n c i s c o ' s m i n d , t h i s f a r f r o m equilibrium process lives: "If a physical system is autopoietic, it is living."Described as a mechanism, autopoiesis makes the link between physics and biology: "The phenomenology of living systems is then the mechanicist phenomenology of the physical autopoietic machines [...] with purely mechanicist notions, true for every mechanicist phenomenon in any space, one can explain completely this organization and its origin."(Varela, 1979) 7   Organizational closure: the general logic of embodiment The fundamental salient feature of this framework of autonomy is the circular, closed, self-referential characteristic of the organization of the living system, which creates a minimal distinction between an interior and an exterior, and guarantees the continuous dynamical, mechanic generation of the stable "internal coherence" of an autonomous system (Varela and Goguen, 1 9 7 7 ) .T o d e l i n e a t e t h i s c i r c u l a r organization and causality at work in the network of co-dependencies of such systems, Francisco proposed, within the framework of what he called a "systemcentered" logic, the general concept of organizational closure or operational closure.
"Closure" is the circular mechanism defining the class of self-organizing systems in general. 8Autopoietic systems are "a particular case of a larger class or o r g a n i z a t i o n t h a t c a n b e c a l l e d organizationally closed" (Varela, 1979).
For Francisco this concept was essential for an understanding of the condition of a living system: "in order to study life and cognition, we need to explore the almost entirely unexplored land of autonomousclosure machines, clearly distinct from the c l a s s i c a l C a r t e s i a n i n p u t -m a c h i n e s " (Varela, 1984a).
Closure is a response to the attempt 1) to f o r m a l i z e a n d t o c h a r a c t e r i z e t h e mechanism of "autonomy in general" as a self-organizing behavior and 2) to specify the circular organization or mechanism of a given autonomous system as it gives rise to its specific identity: closure accounts not only for the "uniqueness" of Life but also for its "diversity" (Varela, 1981).The observable specificity of living beings indicates that there is species-specific organizational closure.Each system has its own way of being operationally closed.Organizational closure specifies the domain of interaction of the system with its surroundings, conditioning its possible ways of coupling with the environment.In higher organisms, the meshwork of cod e p e n d e n c i e s i n c l u d e s t h e d i f f e r e n t physiological systems (cardio-vascular, respiratory, nervous, immune, etc.), and t h e i r s u b -s y s t e m s .T h e c o m p o n e n t s involved and the kind of interactions to be considered depend upon the type of autonomous systems to be considered at (cells, organisms, animal populations, ecological systems).
Moreover, there are two aspects of closure: organizational, which defines the possible interactions in a "static" circular framework, and operational, i.e. the recurrent dynamics that closure elicits. 9As such, the concept of closure aims to introduce a "universal mechanism for stabilization."Identity is always identity in time, and exists in relation to an environment with perturbations that must be compensated for.This process of recurrent stabilization, involving internal circular processes with matter and energy flux, is at the core of the dynamical persistence of the autonomy and wholeness of the system.As a whole, the system exists a n d s u b s i s t s o n l y i n s o f a r a s i t i s organizationally closed.When a system no longer has organizational closure, it is no longer in its domain of viability, and therefore dies.
It is essential to understand that the idea of closure does not contradict that of openness.Closure doesn't mean a closed system.We are looking at far from equilibrium systems, with an exchange of matter and energy with their surroundings (Varela , 1977a).The core of circular causality is coupled with the system's trophic and adaptive dependence on its environment.Francisco always emphasized that a system is "not separable from its interaction domains" (Varela, 1980a).
Francisco's thesis maintains that every system-whole is organizationally closed: "The wholeness of a system is embodied in its organizational closure.The whole is not the sum of its parts; it is the organizational closure of its parts" (Varela and Goguen, 1977).
This last point must be kept in mind in the following paragraphs.It can be seen as the fundamental feature and the first theoretical definition of embodiment.

Intuiting the dynamic core
The adaptations and highly complex behaviors of animals sometimes make them appear as if they had their own 'project,' as if they had an intrinsic intentionality.However, notions such as those of 'goal' and 'purpose' come from a realm of discourse proper to observers describing and somehow summarizing the behavior of a system.Since they overlook the effective 9 The system's stability is dynamic.It centers on a huge internal movement, a perpetual flow.Therefore, autonomy is the result of the set of possible internal transformations or endomorphisms [S n => S n ] defined by the system closure into its domain or state space.The indefinite recursion of component interactions, sustained through systemic re-entries, has the central role in the flux of constitution of the system.(Francisco referred to Wiener who introduced the fundamental revolutionary concept of feedback).As we are considering real physical processes, the scientific paradigm for such a concept, beyond a general theory of systems, would be biophysics.The whole dynamical process that organisational closure defines can thus be represented, in a very general way, by a system of non-linear differential equations: including the set x of co-dependent variables, the set of interaction laws S, and a space of internal and external parameters p (we have drawn the generic properties of such a system in Figure 1).If in such a formalism the closure remains implicit, "the stability of a dynamical system can be considered as the representation of the operational closure of an autonomous system" (Varela, 1979).
RUDRAUF ET AL. Biol Res 36, 2003, 21-59 subjacent processes, for Francisco they are "purely pedagogical." 10 Francisco considered it important to envision the system from the perspective of "its operation, which always unfolds in the present, as in every determined system" ( V a r e l a , 1 9 7 9 ) .H e e m p h a s i z e d t h e "necessity to understand that cognition or behaviors are operational phenomena without final cause: they work in a particular way.Intentionality is an interpretation of the observer.Coherence is a fact and not a 'supposed design'" (Varela, 1986b).As we have already noted, for Francisco, the only interactions being carried out in organisms on the level of continuous processes are mechanistic ones.
Thus, the vital "bringing forth" (Varela, 1990) exhibited in living beings, (that we perceive, for instance, as a struggle for life), can be seen as purely a consequence of their mechanical operation: "the closure and the identity of a system are imbricated in such a way that an operationally closed system necessarily subordinates every transformation to the conservation of its identity" (Varela, 1979).This maintaining of identity is a result of its operation, not finality.Thus, from a mechanical point of view, what we observe as intentional behaviors are, Francisco claimed, simply the operational persistence of specific processes (Varela, 1980a).From the point of view of closure, "a system is adaptive s i m p l y b e c a u s e i t s o r g a n i z a t i o n i s maintained invariant through changes of structure which do not violate constraints."(Varela, 1984a).In a purely descriptive account, an intentional act, as it appears to the observer, is a mechanical succession of dynamical processes of convergence toward a certain state, a transitory persistence of the coupling between the system and its environment.
This notion of persistence, which is related to stability and has its origins in operational closure, was fundamental to F r a n c i s c o ' s c h a r a c t e r i z a t i o n o f t h e organism as a bringing forth of an identity.Such identity is maintained in spite of all the perturbations that affect it.In this sense, we can say that it possesses somehow a certain force of inertia (Varela, 1997a). 11.
In order to account for the "bringing forth" (Varela, 1990) carried out by living systems, we will use the concept of "dynamic core" (Edelman and Tononi, 2000), although it is not a term Francisco used (the issue is developed on the scale of brain dynamics in Michel Le Van Quyen's paper here) 12 .

The eigenbehaviors and the dynamic core
Although it is fundamentally characterized by its organizational identity, every living s y s t e m s h o w s s p e c i f i c s t r u c t u r a l transformations, some of which correspond to what we usually call behaviors.The internal, dynamical side of this observable e t h o l o g y 13 , f r o m F r a n c i s c o ' s p u r e l y operational, non-functionalist perspective, is the presence of self-organizing dynamical tendencies shaping the ongoing, specific 10 Francisco always criticized "the naive use of information and purpose," which indicates a " lack of a theory for the structure of the system [...] of a theory of the kind of machines living systems are" (Varela and Maturana, 1973).They do not belong in the definition of the system itself.Against a purely functional characterization of the system leading to teleological views (certainly useful for communication, but lacking the nomic intermediate), he always gave priority to "material interactions," prediction and causality (through a network of nomic relationships).However, Francisco considered the role of observer in the constitution of meaning to be irreducible: "The theory illuminates the subject, and the subject is what makes theorizing possible" (Varela and Goguen, 1977).He sometimes admitted the concept of teleonomy, i.e. causal processes under abstraction, and, in a collaborative work with Andreas Weber he supported some form of teleology in biology.They distinguished between external, seemingly purposeful design, which was Darwin's main concern, and an intrinsic teleology that, on the contrary, is concerned with the "internal purposes immanent to the living."In relation to this latter case, they defended the idea that one can go beyond the simple "as-if character" of natural purposes and grasp "immanent teleology as a truly biological feature."(Weber and Varela, 2002) "attitudes" of the system.Francisco called them "eigenbehaviors" (own-behaviors) (Varela and Goguen, 1977;Soto-Andrade and Varela, 1984).Eigenbehaviors are s p e c i f i c , p r e f e r e n t i a l , i n t e r n a l transformations that are recurrent in the state space of the system (Fig 2).They possess the following properties: a) an eigenbehavior is a global observable state of the autonomous system under study; b) it is specified by the organizational closure of the system; c) it expresses the coherence of the system's operation; d) it relies on internal cooperative interactions; e) it is not separable from the history of structural c o u p l i n g o f t h e s y s t e m w i t h i t s surroundings.The richness and complexity of a system is therefore based on the intricacy of its landscape of eigenbehaviors.
Michel Le Van Quyen discusses (this issue: Le Van Quyen, 2003) how such g e n e r i c o r s y s t e m i c p r o p e r t i e s a r e fundamental for orienting our search for scientific tools that address the issue of the dynamic core.Francisco studied the notion of eigenbehaviours using concepts issuing from mathematical and physical paradigms such as chaos, complex systems, dynamical systems theory, morphodynamics, selforganizing criticality, synergetics, far from equilibrium thermodynamics, coupled nonl i n e a r o s c i l l a t o r s , e t c .A l l o f t h e s e p a r a d i g m s p r o v i d e d t o o l s f o r operationalizing and understanding the emergence of dynamical regularities in living systems, and their tendencies to shift from one to another of their preferential regimes.Concepts like attractors in phase space (or state space), differentiable flow, morphodynamical field, phase transitions, bifurcations, fluctuations etc. constitute powerful tools for characterizing the dynamical properties of living systems.

The central nervous system as a closed network
The brain occupied a central place in Francisco's theory.Given the nervous system's complexity and its properties of connectivity, the brain stands out as an ideal candidate in the living world to actually embody a foundation for the dynamic core and to play a critical role in the self-organization and complexity of the system's eigenbehaviors.
Francisco's more recent views on brain dynamics (Varela et al. 2001;Varela 1995b) 14 are rooted in conceptions he developed earlier in his work (Varela, 1977b), that were influenced by "new" convergent trends: the re-discovery of the issues around self-organization in physics, and the re-discovery of self-organizing procedures in AI (neo-connectionism).In 1 9 7 9 , h e w a s a l r e a d y i n t e r e s t e d i n Always transient, such eigenbehaviors can be seen as unstable dynamical tendencies in the trajectory of the system, represented here in an abstract state space.They suggest the existence of self-organizing dynamical laws mechanically producing, through internal cooperative interactions, the richness of the system's behavior and constituting its "dynamic core."(see Le Van Quyen, 2003, in this issue for technical developments) "explaining the emergence of large scale coherences in complex neural-like nets," emphasizing that "statistical reasoning could be used to characterize generic behaviors of the network" (cf.Varela, 1986a).
Following Maturana (1969), and using the same logic used for autonomous systems in general, Francisco proposed "moving towards viewing the brain as a system characterized not by its inputs, but by the operational closure of its dynamics of s t a t e s , " a s a c o m p l e m e n t t o t h e c o m p u t a t i o n a l i s t v i e w o n c o g n i t i v e processing (Varela, 1984b;Varela, 1977b).Francisco and Maturana insisted on the closed and recurrent character of brain organization: "the nervous system is an operationally closed network of neurons in interaction" (Varela, 1979).
Although the central nervous system appears to the neuroanatomist as a very hierarchical and differentiated system with strong functional divisions (such as the sensory-motor division), its internal recursiveness led Maturana to state: "the nervous system, as a mode of organization, seems to begin at any arbitrary point that we may choose to consider" (Maturana, 1969).Inspired by Erich von Holst and Mittelstaedt, Francisco referred to the highly recurrent neuroanatomical structure o f b r a i n n e t w o r k s a s t h e " L a w o f Reciprocity": "if a region A-say, a cortical area, or a specific nucleus-connects to a n o t h e r r e g i o n B , t h e n B c o n n e c t s reciprocally back to A, albeit by a different anatomical route." The kinds of operations taking place in t h e b r a i n d e p e n d s t r o n g l y u p o n i t s interconnectedness, its recurrent graph of connectivity, showing very specific, reciprocal (neuroanatomical) mappings between various distributed internal brain surfaces, with highly differentiated subnetworks.As a consequence of these massive re-entries (reciprocal connections), the brain shows a sustained endogenous activity (cf.Edelman and Tononi, 2000).Examples of this are the oscillatory behaviors elicited by the intertwining of the reticulo-thalamo-cortical networks, the cortico-cortical networks and the corticostriato-thalamo-cortical networks, which can be indirectly observed through the brainwaves in EEGs or MEGs.Neural eigenbehaviors emerge from among these endogenous oscillations through distant, non-linear, recursive interactions in distributed neural networks (Varela et al, 2001; cf.Le Van Quyen in the same issue). 15e note here that, as for organizationally closed systems in general, closure in the brain is not incompatible with openness.The central nervous system is, of course, open to interactions with the body and its surroundings in a circular mode, as will be extensively developed in the following sections on embodiment.The vision of the brain as a "closed" network, as emphasized here, is intended to highlight its power of e n d o g e n o u s s p o n t a n e i t y a n d s e l fo r g a n i z a t i o n .S u c h c l o s u r e a p p e a r s naturally as an important source of organization of the system's dynamic core.

A u t o n o m o u s s y s t e m s a r e m u t u a l l y embedded subsystems
Through the concepts of autopoiesis and operational closure we have introduced the general characteristics of the kind of machines humans are: autonomous systems.As the example of the brain as a closed system that is nonetheless open to its environment has shown, one of the features stressed by Francisco is that we are constituted of many embedded sub-systems in interaction (Fig 3).
An organism (and this is particularly true for higher organisms) is composed of highly differentiated structures and organizations, including many long distance physiological interactions between the multiple subsystems it contains (for example organs, on a macroscopic scale, and cells on a microscopic one).The autonomous system as a real biophysical entity is spatially and functionally distributed.Moreover, the interactions are costly in time and energy; thus one can consider the many sub-systems in the organism as having a certain autonomy relative to others.Some subsystems have a certain degree of closure due to both their specific internal processes and time constants, and to the long-range c o n n e c t i o n s t h a t r e s t r i c t p o s s i b l e interactions among sub-systems to a finite delay.According to Francisco, this relative autonomy is particularly obvious in the immune network and the nervous system.
Naturally, the definition of a "sub-system" is always somewhat arbitrary. 16For instance, in an autonomous framework, the brain, as a sub-system, can be viewed as a controlled system that is hierarchically dependent on the rest of the system, the individual body.Yet the brain can also be s e e n a s a n " a u t o n o m o u s " c e n t e r o f behavioral organization for the body: "the n e r v o u s s y s t e m , t h e b o d y a n d t h e e n v i r o n m e n t a r e h i g h l y s t r u c t u r e d dynamical systems, coupled to each other on multiple levels"; they are "mutually embedded systems" (Thompson and Varela, 2001).
It can be deduced from such a circular distributed framework with multiple different embedded time constants and biophysical pathways of interactions, that autonomous systems are fundamentally recurrent systems with delays.This multiplication of the recurrent levels of interaction can be a source of selfperturbation in the system, the properties of which we will look at later in this article.Such an embedded organization, with the high level of constraints of mutual influence b e t w e e n d i s t r i b u t e d s u b -s t r u c t u r e s (involving a finite time of propagation in physiological, biochemical, or even b i o m e c h a n i c a l n e t w o r k s ) m a k e s t h e system's dynamics highly non -linear17 .FIGURE 3 -The autonomous system as a mutual embedding of subsystems.Diagramatic evocation of a "hierarchy" of system levels: systems S i-1 * , S i-1 ** , S i-1 *** , … of level (i -1) constitute system S i j at level i; similarly, systems S i * , S i ** , S i *** , …of level i constitute system S i+1 at level (i+1); and S i+1 together with other systems of level (i+1) will constitute a system at level (i+2); and so on, upward and downward.The organism is thought of as an organizational closure of interacting sub-systems.
Since the identity of the system depends on the dynamics of its mutually embedded systems, it is perpetually at risk of breakdown, of divergence; it is, so to speak, "operating at the edge of chaos."Identity is intrinsically precarious and intrinsically fragile. 18ELFLESS SELF, EMBODIED MIND After having sketched out the basics of Francisco's theory of autonomy and operational closure, two actors take on particular importance in his approach: the whole individual as an autonomous system and a fundamental level of organization, and its brain, as an organizing embedded sub-system.
In this section we will try to specify how Francisco conceived the "shaping" of a mind within such a framework of autonomy and circular causality by means of a first step towards the concrete phenomenology of the embodiment.It is indeed essential to keep in mind that we are not only talking about an abstract way of dealing with the fundamental properties of the living, but also about our own organizational and dynamical condition in the concrete domain of our flesh, which is at the root of our experience (Varela et al, 1991).
Francisco's entire conception of mind and ultimately of experience is concerned with the constraints exerted by the specific phenomenology of our concrete coping (Varela, 1999b) upon our internal dynamics as autonomous systems, and reciprocally, the effects of the latter upon the former, in a circular framework.Thus, his approach is grounded in "the disenchantment of the abstract" and the "re-enchantment of the concrete" (Varela, 1995a).He rejected purely computational, logical, views of the mind in favor of a "concrete, embodied, lived" description of the processes.In keeping with his systemic framework, his approach to embodiment proposes an original way to define the problematic "locus" of the mind.

Basics of Embodiment
According to Francisco, if we want to understand what the mind is, it is not enough to observe the specific brain structures involved in the functioning mind.There is a gap in terms of insight when we try to make the realm of mind fit into a brain structure or even into a brain response.This does not mean that some parts or subprocesses of the system are not more crucial than others for the emergence of subjective experience and consciousness, just as there are organs that are more vital than others.Certainly, the loss of certain parts of one's body or one's brain (after an accident for instance), does not generally lead to the disappearance of the properties that make us "minded" subjects (although often they appear very altered); nonetheless some substructures in the brain, as well as some specific processes, appear crucial and limiting for the constitution of mind or the possibility of consciousness. 19These substructures are only critical nodes for the mind's functioning.They cannot be the mind itself. 20uch considerations led Francisco to a dramatic conclusion: "the mind is not in the head" (Varela, 1999b;Thompson and Varela, 2001).
The domain of constitution of the mind must therefore be sought in "brain-bodyworld divisions" and certainly not in "brainbound neural events": "we conjecture that consciousness depends crucially on the manner in which brain dynamics are embedded in the somatic and environmental context of the animal's life, and therefore that there may be no such thing as a minimal, internal neural correlate whose intrinsic properties are sufficient to produce conscious experience" (Thompson and Varela, 2001).
The first step, Francisco claimed, is to consider that "the mind cannot be separated from the entire organism.We tend to think that the mind is in the brain, in the head, but the fact is that the environment also includes the rest of the organism; includes the fact that the brain is intimately connected to all of the muscles, the skeletal system, the guts, and the immune system, the hormonal balances and so on and so on.It makes the whole thing into an extremely tight unity.In other words, the organism as a meshwork of entirely co-determining elements makes i t s o t h a t o u r m i n d s a r e , l i t e r a l l y , inseparable, not only from the external environment, but also from what Claude Bernard already called the milieu intérieur, the fact that we have not only a brain but an entire body" (Varela, 1999b).As a consequence of closure, this irreducible embodiment of our biophysical structure appeared to Francisco as a radical prison : "We can't get out from the domain defined by our own body and our nervous system.Only one world exists for us: the one we are experiencing by these physiological processes that make us what we are.We are taken in a cognitive system, from which we can't neither escape, nor chose where it begins or how it works" (Varela, 1988a).
We frequently talk about sensory-motor or action-perception loops.Francisco is known for his enactive approach, in which the system's "coping" is described as 1) mediated by perpetual sensory-motor loops and 2) mediated by the ongoing endogenous pattern of its brain activity, defining the specific "coupling" of the system with its surroundings (Varela et al, 1991) (Fig 4).
In his last article with Evan Thompson (Thompson and Varela 2001), he proposed the concept of "cycles of operation" referring to the multi-level specific phenomenology of the individual concrete operations taking place during integrated sequences of behavior, in which cognitive acts and mind take place.Through a highly specific phenomenology, the cycles of operations include, notably, organismic regulation, ongoing sensorimotor coupling, c o g n i t i v e a c t s a n d i n t e r -i n d i v i d u a l interactions (Thompson and Varela, 2001).The drama of the "cycles of operation" occurs, therefore, within a very particular field of constraints, that of the entire organism and its surroundings.
The minimal level of the operational cycles is thus the brain-body system.Francisco described early on the generic circular causality between brain and body as follows.1) The organism, including the nervous system, is the physical and biochemical environment of the autopoiesis of the neurons and other cells.It is therefore a source of physical and biochemical p e r t u r b a t i o n s w h i c h t r a n s f o r m t h e properties of the neurons and lead to couplings 2 and 3. 2) Certain physical and b i o c h e m i c a l s t a t e s o f t h e o r g a n i s m transform the state of activity of the neural network by acting on the membrane receptors of certain neurons, leading to the coupling 3. 3) Certain states of the nervous system change the state of the organism and lead anew to couplings 1 and 2. (Varela, 1979).
As implied by the enactive approach, this embodied (brain/body) conception of the mind's functioning through cycles of operation, that include at a certain level subjective sequences, does not, of course exclude the grappling with the environment.The embodied mind is not a "solipsist ghost" (Varela, 1991).It works in the "body-inspace," which contributes to its shaping.The ongoing, endogenous regimes of activity in the brain embedded in the rhythms of organism regulation and physiology, must be conceived as taking place within a constant sensory-motor c o p i n g b e t w e e n t h e s y s t e m a n d i t s surroundings: "animality invents a mode of being which is inseparable from movement, going towards, seeking in movement" (Varela and Depraz 2000).
In accordance with the views of the philosopher Merleau-Ponty, the sensory processes of the brain are conceived in direct relation to the organization of the motor eigenbehaviors of the whole system, i.e. its ethology.Motor behaviors define how sensory interfaces will be modulated in a specific situation: "the state of activity of sensors is brought about most typically by the organism's motions" (Varela, 1991).Thus, given this intimate link between brain activity and action, we must consider the "situatedness" of the autonomous systemits particular engagement in specific situations-as fundamental to the "neurologic." From the standpoint of Francisco's enactive perspective (Varela et al, 1991), the system lends significance to its surroundings, creates a meaningful world through its organizational closure, a world that the environment doesn't possess by itself: "like jazz improvisation, environment provides the "excuse" for the neural "music" from the perspective of the cognitive system involved" (Varela, 1991).But if, in Francisco's view, the environment doesn't contain pre-defined information that is independent of the "domain of coupling" that the autonomous system defines, it literally in-forms the system's coping21 .
As a complex, distributed, circular biophysical system that is self-affirming, "the body is the place of intersection of the different identities emerging from closure, which makes it so that inside and outside are intricated.We are and we live in such an intertwined place.Our body doesn't have a single external identity alone but constitutes a meshwork divided and intertwined without any other solid f o u n d a t i o n t h a n i t s o w n p r o c e d u r a l [processuelle] determination" (Varela and Cohen, 1989).

So, what is embodied?
The notion of "cycles of operation" (Thompson and Varela, 2001) conceptually circumscribes the deployment of the embodied mind as a process that takes place in a context of constant coping.It provides the understanding of mind with a kind of "unity of action," that evokes its dynamical status and temporal extension.Here we will look more closely at how Francisco approached the issue of the locus of this embodied mind.The central problem is therefore how to define the correct level of existence of what we intuitively call the mind.
The term itself, em-bodiment, refers to something immanent to the system, shaping its way of being in the world, its way of being coupled.In Francisco's view, cognition was nothing other than this dynamical "coupling" (Varela, 1981;Varela, 1983).From a phenomenological point of view, in our daily apprehension, our mind appears as a very integrated phenomenon, which extends beyond conscious experience; it behaves as a global phenomenon actively asserting its identity, our identity, with a certain autonomy.We could say that, as such, the mind behaves as a self-concerned cognition, or, in the framework of autonomous systems, a mode of persistence, i.e. a dynamic core, associated with a way of interacting, often with itself.
Francisco liked to use intuitions from our daily experience, and considered it as a valid domain of investigation.He illustrated the irreducible "global" nature of the mind as embodied through the way we as humans interact among ourselves.For you, I'm an entity that interacts with you in a noncompact temporal process (if you look at t h e p r e c i s e p h e n o m e n o l o g y o f o u r interactions): my answers to your questions, as you can see when you are waiting for them, take time; my mind's operations take time.My concrete mind also acts as an actual though indirect level of coupling, which you can perceive through our sustained exchange and communication, that involves a global synergy of corporal operations engaging me as an individual.This global level of me as an individual appearing in our mind-related interactions is "a mode of existence of which you cannot say it doesn't exist.('Francisco doesn't exist')", and without which nothing real would remain of what leads you to see me as minded or imbued with a subjectivity.There is a domain of mutual coupling and mutual determination in which the personwhole is brought forth.This ontological level of the behaving whole in my body cannot be denied.As soon as you try to reduce it to independent sub-systems, you lose it.This resistance to reduction is the direct expression of its systemic nature.Francisco claimed: "I'm an integrated, more or less harmonic unity that I call 'myself' or 'my' mind, and you interact with me at that level: 'Hi, Francisco.'That interaction is happening at the level of individuality, which is the global, the emergent.Yet we know that the global is at the same time cause and consequence of the local actions that are going on in my body all the time" (Varela, 1999b).Thus, from both the biophysical and the concrete experiential points of view, there is no central "I," other than the one sporadically actualized in a l i n g u i s t i c , s e l f -r e f e r e n t i a l m o d e i n communication.The "I" can only be localized as an emergence but it acts as the center of gravity of the subject himself, of his real-life experience" (Varela, 1993).
So, "if the mind is not in the head, where the hell is it?"The answer takes the form of an enigmatic paradox: "[that's] precisely the point here: it is in this non-place of the co-determination of inner and outer, so one cannot say that is outside or inside" (Varela, 1999b).My mind is a "selfless self" (or "virtual self"): "a coherent whole which is nowhere to be found and yet can provide an occasion for coupling" (Varela, 1991).Because of its radical embodiment, the mind is not a substantial mind: "The mind neither exists nor does it not exist [...] it is and it isn't there" (Varela, 1999b).Finally: "it does not physically or functionally reside anywhere" (Varela, 1997c).
If we want to insist on looking at the mind objectively, as a "cycle of operation," that we can describe, we might be satisfied with considering it as a spatially and temporally distributed process that behaves in a way that corresponds to a "mind."The mind as a phenomenology in action, viewed from either a first-or a third-person perspective, can be described as a behavior, literally situated in a specific cycle of operation.Francisco thus conceived of it as a "behavioral cognition" working "at the level of a spatially behavioral bodily entity" (Varela, 1991).The notion of "behavioral cognition" equates having a mind with having a particular behavior.Francisco asserted that each of us, as a "minded" living being, is a dynamical process open to interaction with others and itself.The "locus" of the mind is an "emergence through a distributed process" within the organizational closure.But, as a process of organization, "a non-substantial self can nevertheless act as if present, like a virtual interface" (Varela, 1991).
H e r e w e m u s t b e c a r e f u l n o t t o misinterpret Francisco: as we said earlier, he had no doubt as to the mechanical origin of this global entity."Virtual entity" (Varela, 1997c) or not, dualism and functionalism are excluded.As stated in the first section with respect to the fundamental expression of embodiment, all wholeness in the physical space is the organizational closure of its parts, and, as s u c h , i s r a d i c a l l y e m b e d d e d i n i t s interacting constituents and processes and is continuously generated by them.Mind is an aspect of the "pattern in flux" in which our concrete, biophysical being lives (Varela, 1999b).It depends on multiple levels of constitution, and is a way in which the system is coupled within itself and with the environment.
A s s u c h , i t c o n s e r v e s t h e g e n e r a l properties of the autonomous systems described above.That is, the mechanical conservation of an identity, brought forth by an internal dynamic core, in a specific embodiment, giving rise to a history of coupling through the particular coping of the system with its environment, defining regularities and making a particular being in the world.As a biophysical process of "bringing forth" identity, it is not surprising that phenomenologically our mind has a self-affirming quality.Physically, this operation of "bringing forth" can be related in part to the non-linear dynamics of the brain, since the brain is the strongest source of self-organization in us and the most plastic one: "the operational closure of the nervous system then brings forth a specific mode of coherence, which is embedded in the organism.This observable coherence is a cognitive self : a unit of perception/motion in space, sensory-motor invariances mediated through the interneuron network [...] the cognitive self is the manner in which the organism through its own selfproduced activity becomes a distinct entity in space, but always coupled to its corresponding environment from which it remains nevertheless distinct" (Varela, 1991). 22Thus, from the point of view of the external observer, the experimentalist for example, who must voluntarily distance himself from the natural coupling with his object, this cognitive self evokes the embodied waves of an active dynamic core reverberating through the entire living body.Its determination, or persistence remind us of what we usually think of as will.
As embodied acting selves, we are a global dynamical process, in a dynamical equilibrium, emerging and acting from interactions of constituents and interactions o f i n t e r a c t i o n s : " o r g a n i s m s , t h o s e fascinating meshworks of selfless selves, no more, nor less than open-ended, multilevel circular existences, always driven by the lack of significance they engender by asserting their presence" (Varela, 1991).
However, Francisco viewed the body as a dynamical "locus where a corporal ego can emerge" (Varela and Cohen, 1989).This issue of the ego giving rise to a sense of self must be situated in Francisco's theory in a very particular field of causality, that shapes embodiment.

T h e m o r p h o d y n a m i c a l f i e l d a n d i t s dialectics with the dynamic core
With the notion of the cycle of operation we have begun to specify the nature of the system's coping and the notion of the selfless self as a dynamical, embodied expression of the dynamic core at work in the individual.But how does the selfless self take on a form so that it "looks like" our experience from the inside?The lived ego of the embodied mind must be thought of as the continuous shaping of the dynamic core.But again, beyond the basics of the specific medium of our embodiment sketched above, it is essential to understand the levels of causality at which the embodied coping, that constitutes our mind, occurs.One of the fundamental sources of shaping, according to Francisco, was the body shape itself: " the most specific property of multicellular organisms is to show a form.This last one gives a body to their operational closure and become the key to understand many dimensions of their operations" (Varela, 1988b).
If there is a "reciprocal determination" (Varela and Frenk, 1987) between global structures and parts of systems, as the hypothesis of closure implies, the specific structural and morphological organization of the body must have a "structuring" causal role.According to Francisco, shapes or forms in themselves, of the whole body as well as of its parts, should have a causal role in the dynamics of the system.They are an "ongoing medium" and a "specified/ specifying space:" "The intuition behind our framework is that space is a constitutive element in the dynamics of living organisms just as much as the solidity of their molecular constituents" (Varela and Frenk, 1987).Now, we are dealing with what we could call a "dense" living body, perpetually acting, moving, transforming from one eigenbehavior to another in its cycles of operation, in such a way that more than e x t e r n a l s h a p e , i t i s t h e g l o b a l morphodynamical behavior of its integrated structures which appears central to the way i t b e h a v e s a s a w h o l e a u t o n o m o u s organization.The field of embodiment is a morphodynamical field. 23In Francisco's framework this concept complements the more general notion of organizational c l o s u r e .A p p l i e d t o t h e i s s u e o f embodiment, it emphasizes the constraints that instantaneous morphological states of the body can exert on the whole system.Of course in the case of a biological organism this is an abstraction which must be conceived of as acting through specific functional or biomechanical pathways in a specific organizational closure.
Francisco called for "a research program in which to understand biological shape," and its "morphodynamical constraints" (Varela, 1988b).Such morphodynamical constraints can be found in the biomechanical degrees of freedom of a specific body, defining a limited set of possible behaviors, as well as in its specific visco-elastic responses to perturbations.The dynamics of internal liquids are also very important.Francisco considered that the extracellular matrix (ECM)-the extracellular medium which forms a "continuum" and links all the body parts to make a whole-was a very important biomechanical medium for morphodynamical causality: "As in the notion of a field and its corresponding particles, there is in living shape a dynamic complementarity: the entire global shape of the body affects the local conditions for the ECM/cell relationship, but at the time the local dynamics conditions how the entire body is actually built" (Varela and Frenk, 1987) 24 .The body organs and tissue mechanics as well as the properties of deformation of the muscular-skeletal and tegument systems should also play a fundamental role in the shaping of the endogenous dynamics of the whole system.All these levels of mechanical causality can affect the whole system and its dynamic core through the interconnections of its organizational closure, i.e. through nervous, hormonal and mechanical pathways.At the most integrated level, posturology can be understood as an initial or boundary condition for the enactive dynamics of the system, to which the internal morphodynamics of the brain's eigenbehaviors, in a shaped sensorymotor coupling, responds.
Within such a framework, the "cycles of operation" referred to above become "morphocycles" (Varela and Frenk, 1987).With each sensory-motor cycle in the behavior of the system, a morphocycle is completed, with its causality potential on the evolution of the system's dynamics.
This potential for effective dynamical deformations through the shaped closure of the system is an important point in the consideration of the constitutive role of the 23 Morphodynamics was developed by the French mathematician René Thom and applied in France to cognitive sciences by Jean Petitot (cf. Petitot, 1992), in order to address the physics of natural forms.The notion of field comes from physics, designating the structure of laws of interaction within a space.Although highly developed by Thom and Petitot in many fields, including biological morphogenesis, and for the later study of self-organization in neural networks, the application of morphodynamics to the issue of mind embodiment is barely under construction and is still seeking precise operationalizations.
We thus have a bootstrapping of two terms: (i) a dynamical term that refers to an assembly of components in network interactions that are capable of emergent p r o p e r t i e s : m e t a b o l i c n e t s , n e u r a l assemblies, clonal antibody networks, linguistic recursivity, mind, consciousness ; (ii) a global term which refers to emergent p r o p e r t i e s , i n c l u d i n g c o n s c i o u s n e s s (Thompson and Varela, 2001), which (downwardly) condition the network components: cellular membranes, sensorym o t o r b o d y i n s p a c e , s e l f / n o n -s e l f discrimination, personal 'I', and "the two terms are truly in a relation of co-definition" (Varela, 1991). 29olism/reductionism: a false controversy

T o u n d e r s t a n d t h e g r o u n d w o r k o f
Francisco's thinking about embodiment and causality it is necessary to lay out some important aspects of his "epistemology."His epistemological thought is anchored in his particular point of view on systems and, in particular, in the issue of global/local relations.It is particularly important to keep this in mind, in order to guard against spiritualist or vitalist interpretations of his thinking.He is known to be have a nonreductionist position about consciousness or wholeness, but his non-reductionism has a very specific significance in his theory.It concerns global/local and organization/ structure relationships in a framework that is perfectly compatible with mechanistic accounts.
As we have seen, Francisco claimed that circular processes of closure offer the best approach for understanding the living.He distinguished this point of view from the usual input-output approach of Cognitive Science.He always stressed that "clearly these two views (input and closure) are not contradictory, but the important point is to recognize that they lead to radically different consequences, and to radically different experimental approaches as well" (Varela, 1984a).
He considered both reductionism and holism to be erroneous points of view.The correct position is one that considers the mutual dependency of the two domains of explanation which, in fact, are for him definitively complementary. 30

NEUROPHENOMENOLOGY
The first two sections have followed Francisco's constructive pathway from the emergence of biological identity to its complex evolution into human embodied cognition.The general properties of the biophysical organization in which we subsist as a circular dynamical process have been discussed with reference to concepts such as autonomy, operational closure and circular causality.Objective considerations about the properties of autonomous systems allowed us to understand the generic bases of the emergence of a self, and helped to set u p t h e d o m a i n o f e x p l a n a t i o n b y emphasizing that the problem is radically dynamical.The organism's identity, construed as a dynamical "bringing forth" in an embodied and situated field, has i l l u m i n a t e d t h e m i n d p r o b l e m b y positioning it as a complex dialectic between a dynamic core and the morphodynamical field of the body, emphasizing i n F r a n c i s c o ' s t h e o r y t h e r a d i c a l intertwining of subjectivity and biophysics.Yet, it is important to highlight that, so far, the point of view of the organism has been studied and characterized from the outside, by an observer who basically relies on his/ her own experience of being alive and conscious in order to infer the internal point of view of the agent.
Francisco thought that the precise modalities of this intertwining between our subjective experience and its biophysical roots should be addressed with a rigorous methodology taking fully into account the concrescence of the experiential and phenomenal domains.

The issue
Francisco insisted on the importance of considering the constitution of "experience from the point of view of the subject himself, a lived world" (Varela, 1999d).For Francisco, first-person events are "the lived experience associated with cognitive and mental events" (Varela and Shear, 1999b).31This is the starting point of Neurophenomenology and the level at which all our questioning necessarily begins.
In neurophenomenology, one now deals with a pragmatic approach where the observer, the experimentalist, explicitly takes into account a subject's point of view, conceived as situated and embodied in its own individuated space and time (Bitbol, 2002; for an empirical illustration see Lutz et al, 2002).
As we mentioned before, Francisco had a non-reductionist position concerning "subjective experience" in that he rejected the eliminativist position. 32He also rejected any a priori overrating of subjective experience.Mysterianism (Nagel 1974), which claims that the limitations of our cognition make insoluble the hard problem, leads nowhere.
On the contrary, his approach was grounded in the postulate that in many of its aspects, human experience is not so subtle, evanescent and non-communicable that we cannot circumscribe it.In fact, Francisco postulated the existence of a relatively fixed and finite structural architecture of experience: "we are similarly assuming that human experience (mine as well as yours), follows fundamental structural principles which, like space, enforce the nature of what is given to us as contents of experience" (Varela, 1996). 33lthough non-reductionist in the sense mentioned above, Francisco's proposal goes beyond the simple search for the " n e u r o b i o l o g i c a l ( b r a i n o r b o d i l y ) correlates of consciousness" because simply studying correlates would "leave in the shadow the precise circulation between them" (Varela, 1997b).It would amount to just "putting on one side a list of items or processes, and on the other seeming equivalencies as phenomenological data and separating the two sides by a "mystery" line, a no-man's land left unexamined" (Varela, 1997b).Francisco promoted naturalizing phenomenology as well as " p h e n o m e n o l o g i z i n g " n e u r o s c i e n c e ( V a r e l a , 1 9 9 9 a ) .i .e .n o t t o r e d u c e consciousness but "re-enchant" the concrete of biology itself.
The explanans, the domain of explanation, t h e " l o c u s o f c i r c u l a t i o n " f o r neurophenomenology" (Varela, 1997b), is naturally embodiment : "data rooted in firsthand experience are intrinsically open to a non-reductive naturalization.This is the c e n t r a l t h e s i s t h a t a n i m a t e s t h e neurophenomenological research project, which is only possible if the central issues of embodiment are put at the center of concern both for cognitive science (such as t h e e n a c t i v e a p p r o a c h ) a n d i n phenomenology (such as in the later work of Husserl and its continuation in Merleau-Ponty).In fact, it is in the lived body broadly conceived that one finds "the close relationship" between experience and its grounding (as both Leib and Körper).It is in that region of events that we are given access to both the constitutive natural elements familiar to cognitive science and the required phenomenological data."(Varela, 1997b). 34

A methodological remedy for the hard problem
Neurophenomenology is grounded on a pragmatic will to progressively and systematically "reduce the distance between subjective and objective [...] a way of narrowing the gap between the mental and the physical" (Varela, 1997b). 35 n t h i s p e r s p e c t i v e e x p e r i m e n t a l paradigms and rigorous first person methodologies must be developed in order to "examine experience."This involves " b r e a k i n g w i t h t h e t a b o o o f u s i n g phenomenal data as valid" (Varela, 1999b) and according phenomenal data (Roy et al, 1999) a place as important as t h a t o f o b j e c t i v e , n e u r o d y n a m i c a l , neurophysiological, or biophysical data. 36 o w e v e r , a s i m p l e u n d i s c i p l i n e d i n t r o s p e c t i v e a p p r o a c h i s n o t t h e solution; the 'just-take-a-look' or 'seeing i n s i d e ' a t t i t u d e m u s t b e o v e r c o m e .Neurophenomenology implies "gathering a research community armed with new pragmatic tools for the development of a science of consciousness."This involves a "call for transforming the style and values of the research community itself," in other words, that researchers themselves, as they are specialists in neurosciences for instance, become specialists in the phenomenology of conscious experience: "My proposal implies that every good student of cognitive science who is also interested in issues at the level of mental experience, must inescapably attain a level of mastery in phenomenological examination in order to work seriously with first-person accounts" (Varela and Shear, 1999b).
The idea is that developing the "skill of phenomenological description" is like developing a "know-how," like "learning to play an instrument or to speak a new language"; it is a concrete "training" (Varela and Shear, 1999b).Francisco wanted to initiate within the Cognitive Science "a sustained tradition of phenomenological examination" cultivating "a systematic capacity for reflexiveness" in "our habitual mind stream"37 .
A fundamental aspect of this "training" is that "[it] must be done in the context of a disciplined approach to the intersubjective validation of conscious experience" (Varela and Shear, 1999b).Subjective experience is not completely a "private experience," it can be "shared."Between the first-person account and the third-person point of view, w e c a n w o r k w i t h a n i n t e r m e d i a t e mediation, a "second-person position," "an empathic resonator" (Varela and Shear, 1999a).
Two main long-standing traditions were deeply influential for Francisco.He found in "contemplative traditions" the model par excellence of a rigorous pragmatics for the investigation of consciousness: "We explicitly draw from Asian traditions, B u d d h i s m i n p a r t i c u l a r , a s l i v i n g manifestation of an active, disciplined phenomenology.It [is] not the intention […] to dwell on Asian traditions per se but to use them as a distant mirror of what we [need] to cultivate in our science and the western tradition" (Varela, 1996).
On the other hand, he drew extensively on the work of philosophers like Husserl, Heidegger, the Kyoto school and Merleau-Ponty.These philosophers produced accurate operational descriptions of subjective experience and, in particular, Husserl (cf. Husserl, 1970) proposed a g e n e r a l t e c h n i q u e f o r i n v e s t i g a t i n g consciousness, making it "recognizable" (Varela, 1996): the Phenomenological r e d u c t i o n ( P h R ) .I n f a c t , F r a n c i s c o considered that the husserlian corpus could constitute a research program in itself, a "husserlian neurophenomenology" (Varela, 1997b) 38 .
I n t h e s p e c i f i c f r a m e w o r k o f neurophenomenology, Francisco sketched the process of reduction as: 1) Attitude.a "self-induced suspension of reference to the contents"39 , followed by a "redirection of thought" towards the "process of constitution" of the contents themselves.The attitude is then to "[cut] short our quick and fast elaborations and beliefs, in particular […] putting in abeyance what we consider we think we ' s h o u l d ' f i n d , o r s o m e ' e x p e c t e d ' description.Thus PhR is not a 'seeing inside', but a tolerance concerning the suspension of conclusions that allows a new aspect or insight into the phenomenon to unfold" (Varela, 1996).Furthermore, we must try to make the self-observing reflexive acts as automatic and discrete as possible, as in certain contemplative states, its horizon being a "'pure' (contentless) c o n s c i o u s n e s s " ( V a r e l a a n d S h e a r , 1999b). 40The gesture of reduction can either be self-induced or guided by a mediator through open questions (Depraz et al 2003).In the latter case such questions invite the subject to redirect his/her attention towards the implicit know-how he/she implemented to carry out the task, or towards the texture of his/her experience during its deployment.
2) Intuition.Phenomenological reduction involves a gain in intimacy towards the phenomenal domain of investigation.The v a l i d a t i o n o f t h e p e r t i n e n c e o f t h e experience is therefore grounded on its intuitive "evidence" (as in mathematics): "This gain in intimacy with the phenomenon is crucial, for it is the basis of the criteria of truth in phenomenological analysis, the nature of its evidence" (Varela, 1996).For Francisco: "Intuition is not some fluffy stuff." 3) Invariants.A process of description m u s t f o l l o w i n o r d e r t o d e f i n e phenomenological invariants.Such an extraction of invariants supposes a work on controlled "variations" of the subjective experience, what Husserl called "eidetic variations" in order to specify "the appropriate dimensions of mental states" (Varela, 1996).These descriptive structural invariants must be open to intersubjective validation.Evidence is shared evidence; intersubjectivity is central.4) Training.In order for the method to serve as a concrete pragmatics: "If one does not cultivate the skill to stabilize and d e e p e n o n e ' s c a p a c i t y f o r a t t e n t i v e bracketing and intuition, as well as the skill for illuminating descriptions, no systematic study can mature."41 .Thus training is a f u n d a m e n t a l a s p e c t t h a t r e c u r s i v e l y permeates the proposed methodology at each step.Specific phenomenological states must be investigated through multiple "redone" experiences by the researcher himself.The search for stability naturally opens up the possibility of working with t r a i n e d e x p e r t s u b j e c t s c a p a b l e o f reproducing internal conscious states in experimental situations.

Phenomenological invariants: the formal level
Simple verbal reports are very interesting but, in the end, they are limited.The nature o f p h e n o m e n o l o g i c a l d e s c r i p t i o n s resulting from reduction is essential: " P u t t i n g i n t o p r o p e r r e l e v a n c e t h e structural invariants of experience opens the door for the right domain of formality" (Varela, 1997b).The formal level (Varela, 1999b) appears thus as a fundamental aspect of neurophenomenology.
The adequate spaces of representation for the description of phenomenological experience must be defined in relation to its very nature.Subjective experience appears as a complex multidimensional flux w i t h e m e r g e n t s a l i e n t m o m e n t s o f perceptions, thoughts, imagination, mnesic representations, vigilance variations, attentional shifts, emotional changes, etc. Cognitive operations are embodied in dynamical processes with a temporal texture that is essential in their phenomenology.C o n s e q u e n t l y , p h e n o m e n o l o g i c a l descriptions call for "a dynamical picture" (Varela, 1997b): invariants are dynamical.
From this perspective, Francisco made a "strong" parallel between phenomenology and mathematics (Varela, 1997b).Through his personal phenomenological exploration, he described subjective experience as a real dynamical system.For him the dynamical system paradigm, was the right "bridge" (Varela, 1999a) between the two realms.It is clear that in order to provide operational phenomenological invariants, Francisco was looking for a mathematization of phenomenology.42 "The critical role of formal tools is, in short, based on the Janusfaced nature of mathematical ideals: they provide eidetic invariants which can, in turn, be immediately linked to a naturalistic embodiment or implementation."(Varela, 1997b). 43

Mutual constraints
Francisco described the pragmatic approach of reducing "the distance between subjective and objective" as a search for progressive mutual determination, constraints or circulation: "We need to advance a cognitive science where there is a true circulation between lived experience and the biological mechanisms in a seamless and mutually illuminating manner" (Varela, 1996).
B i o p h y s i c a l o r n e u r o d y n a m i c a l investigations should help to illuminate the domain of subjective experience by constraining it: "it is an axiom that we can only experience what corresponds to our organization" (Varela, 1976).They should also help to validate phenomenological a c c o u n t s b y d e m o n s t r a t i n g t h e i r implementation.
Reciprocally, the domain of subjective experience is the tool for defining what we want to account for, (the structure of consciousness) and for guiding our definition of compatible physical processes.For instance, the dynamical phenomenology of consciousness made Francisco look for a particular type of dynamical neurobiological process.Phenomenology thus becomes a central criterion for the validation of hypotheses about its physical determination: "the novelty of my proposal is that disciplined first-person accounts should be an integral element of the validation of a neurobiological proposal, and not merely coincidental or heuristic information" (Varela, 1996).
Francisco was looking for a profound level of intertwining, at which the relations between both domains would become clear: "this mutual reciprocity without residue is the very nature of the region unique to the körperleib" (Varela, 1997b) (cf. footnote 33).
This belief in the heuristic value of such a n e x p e r i m e n t a l i n t e r t w i n i n g w a s formulated as a working hypothesis: W o r k i n g H y p o t h e s i s o f Neurophenomenology: Phenomenological accounts of the structure of experience and their counterparts in cognitive science relate to each other through reciprocal constraints (Varela, 1996).
T h e d i a l e c t i c a p p r o a c h o f m u t u a l constraints must be seen as a pragmatics intended to provide "generative passages": "the isomorphic idea [between subjective and objective levels] is taken one step forward to provide the passage where the mutual constraints not only share logical and epistemic accountability, but they are further required to be operationally generative, that is, where there is a mutual circulation and illumination between these domains proper to the entire phenomenal domain" (Varela, 1997b).
In Neurophenomenology the subject clearly has a double status: he/she is and acts as a subject in a particular task, but the subject also needs to know about his/her own experience in order to report structural features about his/her experience.Francisco was aware that such a situation raised a fundamental issue: Neurophenomenology requires some degree of self-awareness, even implicit, to provide phenomenological descriptions and structural insights.But this very process of becoming self-aware r e q u i r e d b y t h e t a s k c o u l d b e s a i d paradoxically to introduce unwanted complexity in the data and at the same time to be the very process that science tries to account for.To integrate this aspect of human experience necessarily involved in the implementation of mutual constraints, F r a n c i s c o p r o p o s e d e x p l o r i n g experimentally this gesture of "becoming aware" itself (cf.Depraz et al, 2000).The complete presentation of this issue is beyond the scope of this review (for a recent development see Lutz, 2002).
Francisco was 52 years old when he formulated the neurophenomenological proposal.Despite the fact that he would have only two short years to live, he was able to make significant advances in the essential theoretical and experimental foundations of this great project.

Neurophenomenology of nowness
The first objective Francisco proposed for neurophenomenology was the account of the dynamics of time-consciousness and " c o n s t i t u t i o n " ( V a r e l a , 1 9 9 9 a ) : "constitution" is the term used by Husserl in his Phenomenology to designate the process of construction and emergence of a moment of consciousness.Following H u s s e r l , F r a n c i s c o e m p h a s i z e d t h e Given the importance of integration in brain activity and in behavior, he proposed that transient phase-locking between brain e n s e m b l e s c o u l d b e a f u n d a m e n t a l mechanism of large scale integration in the b r a i n ( F i g 5 ) .H e u n d e r s t o o d s u c h mechanisms to be a "neural glue" that would enhance a specific distributed neuronal ensemble participating in the emergence of a moment of consciousness.The idea is that "it is the precise coincidence of the firing of the cells that brings about unity in mental-cognitive experience" (Varela, 1995b). 47 F r a n c i s c o p r o p o s e d t h r e e w o r k i n g hypotheses: 1) For every cognitive act, there 47 The problem of the perceptual binding brought to the fore the importance of dynamical synchronization in the brain to bind independent functional processes in specialized sensory pathways (Singer and Gray, 1995).Damasio also had proposed the mechanism of large-scale synchronization as an integrative process for memory (Damasio 1989).Early on, Francisco and others emphasized the importance of synchronization in the brain perceptuo-motor unity (Varela et al, 1981;Gevins et al. 1983).Abeles proposed that synchronization could play the role of coherent signal enhancement favoring transmission in neural networks (Abeles et al, 1994).Synchronizations are a natural consequence in interconnected systems with multiple long-range re-entries or reciprocal connections.The convergent process which leads to such emergence of phase-locked coherent ensembles is grounded in the fast ongoing oscillations at work in the brain, in which an important role is given to the gamma band (30-80 Hz), and in the inhibitory-excitatory dynamics of brain networks, not only at the thalamo-cortical level but also at the cortico-cortical one (cf.Varela et al, 2001 andVarela, 1995b for a review).
FIGURE 5 -The moments of consciousness.A diagram depicting the three main hypotheses.A cognitive activity takes place within a relatively incompressible duration, a "cognitive present."The basis for this emergent behavior is the recruitment of widely distributed neuronal ensembles through increased coherence in the gamma band (30-80 Hz).Thus, the corresponding neural correlates of a cognitive act can be depicted as a synchronous neural hypergraph of brain regions undergoing bifurcations of phase transitions from one cognitive present content to another. is a singular, specific cell assembly (CA) that underlies its emergence and operation; 2) A specific CA is selected through the fast, transient phase-locking of activated n e u r o n s b e l o n g i n g t o s u b -t h r e s h o l d competing CAs; 3) The integrationrelaxation processes at the 1-scale are strict correlates of present-time consciousness. 48

Experimental evidence
To study the relations between subjective experience and brain synchronization, mathematical tools for quantifying transient phase-locking between EEG/ MEG signals were developed (Lachaux et al, 1999).The principle was to use complex wavelet convolution of brain signals to extract s i n g l e -t r i a l i n s t a n t a n e o u s p h a s e information, independent of amplitude, and to quantify the stability of phase differences in short integration periods.
EEG recordings were obtained from subjects presented with Mooney faces for 200 ms (Rodriguez et al, 1999), that is, a binary picture representing human faces, easily recognized as faces when presented in upright orientation but usually seen as meaningless black and white shapes when presented upside-down (Fig 6).Subjects had to answer by pressing a button indicating whether or not they had perceived a face during the presentation of the picture.The data was then classified into two groups, the group Perception, and the group Non Perception.In the "Perception" condition, a transient episode of large-scale phase locking between electrodes on the scalp appeared 250 ms after the presentation of the stimulus.This large-scale synchrony occurred mainly in the gamma band (30-80 Hz), and was followed by a strong episode of phase scattering, i.e. desynchronization in relation to the baseline.Only after this scattering, during the motor response, did a new synchronous ensemble emerge.On the other hand, in the Non Perception condition no significant synchronous ensemble appeared after the presentation of the picture.These experiments confirmed the relation between conscious perceptive moments and large-scale neural synchrony in the gamma band.
In a second experiment (Lutz et al, 2002), the neurophenomenological approach was rad i c a l l y d e v e l o p e d .S u b j e c t s w e r e t r a i n e d d u r i n g s e v e r a l e x p e r i m e n t a l sessions to actively categorize their ongoing subjective experience during the 7 seconds rest period that preceded presentation of a three dimensional shape.T r i a l b y t r i a l , t h e y d e s c r i b e d t h e i r experience through verbal accounts, which were recorded on tape.Then, in a dialogue between the experimenter and subjects, phenomenological clusters were defined, with the aim of classifying the i n v a r i a n t a s p e c t s o f t h e s u b j e c t i v e e x p e r i e n c e d u r i n g t h e e x p e r i m e n t a l sessions.Recording of EEG scalp signals was done in the same experimental framework, and subjects were asked to categorize their experience trial after trial based on the previously defined set of phenomenological clusters.Brain data were regrouped according to phenomenological clusters and a dynamical analysis was performed on each cluster.
The outcome of this experiment is c o m p l e x a n d v e r y r i c h .I n a f i r s t implementation of this approach, Francisco and Antoine Lutz studied, for instance, how the precise description by trained subjects of their cognitive contexts (attentive state, thought-processes, strategy to carry out the task) could be used to study the intrinsic variability in the brain responses found during the repetitive presentation of the same visual stimulation.By combining first-person data and the analysis of neural processes, the opacity in the brain responses was reduced and original dynamical categories were detected.This case study offers a nice example of how the careful examination of experience using specific first-person methodology could become a heuristic strategy to provide mutual insights FIGURE 6 -The shadow of perception.Average scalp distribution of gamma activity and phase synchrony.EEG was recorded from electrodes on the scalp surface.Subjects were shown upright and upside-down Mooney figures (high contrast faces), which are easily perceived as faces when presented upright, but usually perceived as meaningless black-andwhite forms when upside-down.The subjects' task was a rapid two-choice button response of whether or not they perceived a face at first glance.Color-coding indicates gamma power (averaged in a 34-40 Hz frequency range) from a given electrode and during a 180 ms time window, from stimulation onset (0 ms) to motor response (720 ms).In the condition where the figures were recognized, transient episodes of largescale synchrony appeared after the presentation of the stimuli, followed by a period of phase scattering and a second period of synchrony during the motor response.Such patterns of synchrony were not present when the pictures were not recognized.Synchrony between electrode pairs is indicated by black and green lines, corresponding to a significant increase or decrease in synchrony, respectively.These are shown only if the synchrony value is beyond the distribution of shuffled data sets ( P< 0.01; see methods, Ref. 18).(from Rodriguez et al, 1999).
concerning the relations between first-and third person accounts.To illustrate the discussion, we will present here one such result in which two phenomenological clusters are contrasted for a given subject (Fig 7).In the first cluster (A) the subject typically reported being prepared for the presentation of the stimulus, aware, with a feeling of continuity when the stimulation occurred, and an impression of fusion between himself and the percept.In the second cluster (B), the subject reported being unprepared, distracted, and having experienced a strong discontinuity in the flux of his internal mental states by the presentation of the stimulus.He described a clear impression of differentiation between himself and the percept.
The main result is the correlation between the features of the subject's subjective experience and the dynamical neural signatures (DNS) of the clusters (Lutz et al, 2002).In the prepared cluster (A) a frontal synchronous ensemble emerges early and is maintained throughout the trial, c o r r e l a t i n g w i t h t h e i m p r e s s i o n o f continuity of the subject.Furthermore, the average reaction time (RT) for this cluster is short.In the unprepared cluster (B), no stable synchronous ensemble can be distinguished during the pre-stimulus period.When the stimulation occurs, a complex pattern of weak synchronization a n d o f s t r o n g p h a s e s c a t t e r i n g (desynchronization) between frontal and posterior electrodes is revealed.Slowly, a subsequent frontal synchronous ensemble appears while the phase-scattering remains present for some time.In this cluster, the RT is longer.The complex pattern of FIGURE 7 -The shadow of perception and feeling within a subjective sequence EEG was recorded from electrodes at the scalp surface.Subjects were shown first a background image with random-dot points.They were asked to fuse two small squares at the bottom of the screen and to remain in this position for several seconds.At the end of this preparation period, a stereogram (3D illusion) was presented.Subjects were instructed to press a button as soon as the shape had completely emerged and to give a brief verbal report of their experience (see section 2.3).Dynamical neural signatures (DNS) of the precise phenomenology of the subjective experience of the subject are presented: (A) brain dynamics associated with a feeling of mental continuity and readiness (154 trials), (B) brain dynamics associated with a feeling of discontinuity and unreadiness with surprise when the stimulation occurred (38 trials).The observed brain patterns (resulting from the selection of the data on the sole criterion of the ongoing subjective experience of the subjects) show dynamical features well correlated with the phenomenology of the subject's conscious experience: the continuity of the mental correlates with the continuity of the synchronous patterns.Color-coding indicates scalp distribution of gamma power around 35Hz normalized compared to a distant baseline ([-8200ms 7200ms], 0 ms corresponds to the presentation of the stereogram).Black and white lines correspond to significant increase and decrease in synchrony, respectively, compared to the baseline.(Modified from Lutz et al, 2002) it a new world emerges: you see clearly that you left your wallet in the store where you just bought cigarettes.Your mood shifts now to one of concern for losing documents and money, your readiness-to-action is now to quickly go back to the store [...] all attention is directed to avoiding further delays." According to Francisco, this caricaturesituation can be applied generally to all our gestures and actions: "new modes of behaving and the transitions or punctuation between them correspond to mini (or macro) breakdowns we experience constantly [...] at each such breakdown the manner in which the cognitive agent will next be constituted is neither externally decided nor simply p l a n n e d a h e a d .I t i s a m a t t e r o f commonsensical emergence, of autonomous configurations of an appropriate stance […] such commonsense, then needs to be examined at a microscale: at the moments where it actualizes during breakdown, the birthplace of the concrete [...] during the breakdown there is a "rich dynamics involving the concurrent sub-identities a n d a g e n t s ." In t h i s p e r s p e c t i v e , phenomenology of behavior tends to fit the p h e n o m e n o l o g y o f o u r s u b j e c t i v e experience: "embodied (sensory-motor) structures are the substance of experience."(Varela, 1999a) The dynamics of neural assemblies presented above could be interpreted from within such a framework.Although dynamically related to the previous moment, they emerge as a breakdown in relation to the previous state of the system.In this perspective, the presence of moments of great phase-scattering between two well separated cognitive acts is very interesting since they are associated with a feeling of discontinuity (Lutz et al, 2002).As noted in Lutz et al (2002) the differentiation in subjective experience is related to microsequences of appearances of discontinuity.
In this light, the fundamental units of constitution of a concrete moment of experience appear to be the activity of coping with impediments, i.e. the coping with very specific micro-situations in our situated cycles of operation, that is, in the present state of our operation as systems.
Such "shaped" breakdowns in cognitive coupling must be envisaged as perturbations of our dynamic core.
To understand how such impeding effects can be lived internally, as sentience, Francisco brought to the fore the field of emotions and affect.Unfortunately, he did not have time to develop fully this last field of his theory.However, by following its internal logic and bringing together the ideas he developed, we can intuit a possible explanation of the final biophysical origin of sentience.

The Nagel Effect: resistance to selfperturbation and sentience
The part of the Francisco's work we introduce here is most likely the least well known, but perhaps the most essential for understanding the biophysical basis of being.Centered on the issue of affects, it permits a synthesis of Francisco's views on embodiment extensively developed in the first part of this article.It might constitute the core of an understanding of what we have called the Nagel Effect, of the subjective experience of having certain physical processes, and so provide us with the conceptual framework for bridging the so-called 'explanatory gap'.
In the last period of his work Francisco (Varela, 1999a;Varela and Depraz, 2000; T h o m p s o n a n d V a r e l a , 2 0 0 1 ) w a s particularly preoccupied with the question of affects and the production of sentience.For him, affect and emotions, "a privileged way for accessing the primordial body" (Varela and Cohen, 1989), played an essential role in mind: "affect or emotion is at the very foundation of what we do every day as coping with the world; reason or reasoning is almost like the icing on the cake.Reason is what occurs at the very last stage of the moment-to-moment emergence of mind.Mind is fundamentally something that arises out of the affective tonality, which is embedded in the body [...] [Mind] starts out from this soup [...] all cognitive phenomena are also emotional-affective" (Varela, 1999b)  49 Going even further, he considered affect as "generative for consciousness itself" (Varela and Depraz, 2000), as a cause of transition from one moment of consciousness to another as well as a cause for the emergence of subjectivity itself.
Since the early days of the development of the concept of autopoiesis, Francisco always rejected the metaphorical use of his concepts, wanting them to be used in precisely defined operational domains.He has been thus reluctant to see the concept of autopoiesis applied to autopoiesis to cultural anthropology or social sciences.Yet in existing metaphors, he often found t h e o p p o r t u n i t y t o r e v e a l o p e r a n t mechanisms by considering their literal meaning.It is in this sense that he mobilizes the concept of affect, which can be considered as a frontier between the realms of objectivity and subjectivity.
He claimed that "affect is a pre-reflective dynamic in the self-constitution of the self, a self affect in a literal sense.Affect is primordial in the sense that I am affected or moved before any 'I' that knows."(Varela, 1999b).
Francisco based his insights about the c o n s t i t u t i o n o f s e n t i e n c e o n h i s phenomenological analysis of affects.Starting with the transition between two moments of consciousness (Varela, 1999a), which is always associated, according to his phenomenological experience, with the feeling of a gradually emerging change, he grounded the dimension "of affect-emotion in the self-movement of the flow, of the temporal stream of consciousness."He emphasized the bootstrap role of emotions through their intrinsic fluctuating character and saw them as control parameters in the initiation of bifurcations between two moments of consciousness: "affect is at the very core of the temporality, and is even, perhaps, its antecedent" (Varela and Depraz, 2000). 50 In his view, "the emergence of the lived present is rooted in and arises from a germ o r s o u r c e o f m o t i o n -d i s p o s i t i o n , a primordial fluctuation.This germ manifests itself in a constellation: an original tendency, a shift of attention, the emergence of salience, the earliest e-motion including a motion that embodies it.Thus this primordial fluctuation cannot be separated f r o m i t s c o m p l e x o r m u l t i f a r i o u s constitution.But it is nevertheless marked by its uniqueness in the unfolding of the living present" (Varela and Depraz, 2000).Inspired by Husserl and James, Francisco and Depraz considered these subjective fluctuations as forces involving whole body transformations: "the affective force m a n i f e s t s a s a r a p i d , d y n a m i c a l transformation from tendency to salience, involving one's entire leib [lived body] as a complex [...] the gamut of autonomic action such as respiratory, heart rate, endocrine secretion, etc., as well as the ancestral motor pattern involved in posture and movement [...] a feeling grounded in the body's responsive repertoire" (Varela and Depraz, 2000).The feeling of emotion appears as "the global Gestalt composed of a variety of feeling dimensions."The 49 He stressed the importance "of the background sensations of the embodiment preceding and grounding all happening cognitive events" (Varela and Depraz, 2000).Francisco distinguished three scale of affect: 1) emotions: "the awareness of a tonal shift that is constitutive to the living present;" 2) affect: "dispositional trend proper to a longer time (hours or days) a coherent sequence of embodied actions;" 3) mood, "the scale of narrative description over a long duration (many days or weeks)." 50This importance of emotions in the making of consciousness represented at the same time a difficulty in a methodological perspective for neurophenomenology: "that's why experience in a phenomenological footnote is so hard to articulate, since a large chunk of its base is pre-reflective, affective, non-conceptual, pre-noetic.It's hard to put it into words, precisely because it precedes words." 51Such a dynamical storm is not incompatible with the fact that emotions are highly regulated processes.The self-perturbations of emotions are induced in the context of integrated neurophysiological responses.As Francisco stressed, living systems show naturally intrinsic instabilities, which are not incompatible with the preservation of their organizational autonomy.On the contrary these instabilities "are the norm" in biological systems (Varela, 1999a) and play an essential functional role as they allow the system to easily shift from one to another of its eigenbehaviors, i.e. to move the current state of the system and the dynamics to a new configuration, in a catastrophic phase transition (an emotion as a stereotyped neurophysiological response is an eigenbehavior).Instabilities are the foundation of the spontaneity of living beings.

IN MEMORIAM
This article is dedicated to Francisco Varela in memory of his innovative work, generous teaching and inspiring life.
F o r h i s o b i t u a r y s e e h t t p : / / psyche.csse.monash.edu.au/v7/psyche-7-12-thompson.html.

FIGURE 2 -
FIGURE 2 -The eigenbehaviors and the dynamic core.Living systems are dynamical systems.They show ensembles of eigenbehaviors, i.e. a specific ethology.Always transient, such eigenbehaviors can be seen as unstable dynamical tendencies in the trajectory of the system, represented here in an abstract state space.They suggest the existence of self-organizing dynamical laws mechanically producing, through internal cooperative interactions, the richness of the system's behavior and constituting its "dynamic core."(see LeVan Quyen, 2003, in this issue for technical developments)

FIGURE 4 -
FIGURE 4 -The operational closure of the embodied system.As a circular process, an individual is engaged in the continuous cycles of operation defined by its eigenbehaviors.Three levels of circular causality are distinguished in the figure: (i) the level of the central nervous system as a closed dynamical system;(ii) the level of the sensory-motor mutual definition of the state of the brain and of the body; (iii) and the level of the ongoing coupling between the autonomous system and its surroundings, including potential inter-individual interactions.