Michel Bitbol

According to Husserl, the epochè must be left incomplete. It is to be performed step by step, thus defining various layers of “reduction.” In phenomenology at least two such layers can be distinguished: the life-world reduction, and the transcendental reduction. Quantum physics was born from a particular variety of the life-world reduction: reduction to observables according to Heisenberg, and reduction to classical-like properties of experimental devices according to Bohr. But QBism has challenged this limited version of the phenomenological reduction advocated by the Copenhagen interpretation. QBists claim that quantum states are “expectations about experiences of pointer readings,” rather than expectations about pointer positions. Their focus on lived experience, not just on macroscopic variables, is tantamount to performing the transcendental reduction instead of stopping at the relatively superficial layer of the life-world reduction. I will show that quantum physics indeed gives us several reasons to go the whole way down to the deepest variety of phenomenological reduction, may be even farther than the standard QBist view: not only reduction to experience, or to “pure consciousness,” but also reduction to the “living present.”

The so-called paradoxes of quantum physics are easily disposed of as soon as one accepts that there are no such things as intrinsically existing particles and their intrinsic properties, but that both particles and properties are relational “observables.” Accordingly, quantum physics does not offer a “description of the outer world,” but rather a prescription about how to make probabilistic predictions within a participatory environment. The latter view looks quite radical with respect to standard Western Aristotelian ontology; but it looks natural in the context of the Indian-Buddhist concept of Pratītyasamutpāda which underpins Śūnyatā. Special attention will then be devoted to the quantum feature of non-separability, which displays remarkable similarities with Pratītyasamutpāda. Finally, the meaning of such twofold parallel between quantum physics and Śūnyatā will be discussed. This parallel will be related to the similarity of epistemological situation between knowing a world from which we are not entirely separated and knowing oneself.

A phenomenological view of contemplative disciplines is presented. However, studying mindfulness by phenomenology is at odds with both neurobiological and anthropological approaches. It involves the first-person standpoint, the openness of being-in-the-world, the umwelt of the meditator, instead of assessing her neural processes and behaviors from a neutral, distanced, third-person standpoint. It then turns out that phenomenology cannot produce a discourse about mindfulness. Phenomenology rather induces a cross-fertilization between the state of mindfulness and its own methods of mental cultivation. A comparison between the epochè, the phenomenological reduction, and the practice of mindfulness, is then undertaken.

In physics, structures are good candidates for the role of transparadigmatic invariants, which entities can no longer play. This is why structural realism looks more credible than standard entity realism. But why should structures be stable, rather than entities? Here, structural realists have no answer ; they content themselves with the mere observation that this is how things stand. By contrast, transcendental structuralism can easily make sense of this fact. Indeed, it shows that when knowledge bears on phenomena, namely on the emergent byproduct of a relation between the explorer and what is to be explored, this knowledge necessarily bears on relations between such phenomena. After a development on the clarifying power of transcendental structuralism, I turn to an early transcendental structuralist interpretation of quantum mechanics proposed by Jean-Louis Destouches. Destouches, an early French philosopher of physics, was a student of Louis de Broglie. He recasted in the 1940 the very concept of physical theory in the light of quantum physics. According to him, whenever phenomena are inextricably relative to the experimental set-up, a physical theory cannot provide anything beyond a list of interconnected predictions for future facts given a relevant class of past facts. In his general mathematical theory of predictions, the Ψ-functions of quantum mechanics do not refer to some “real” waves; they are shown to be nothing but the formal expression of the phenomena’s being relative to incompatible experimental contexts. Since the quantization of variables can itself be derived from a wave-mechanical formalism, it becomes clear that the most prominent features of quantum mechanics are a mere consequence of contextuality. Destouches thus proved that it is easy to make sense of quantum mechanics provided a reflective attitude is adopted. By contrast, too many difficulties arise when one tries at any cost to make quantum mechanics intelligible within a purely ontological framework.

This article aims at reducing the gap between mathematics and physics from a Wittgensteinian point of view. This gap is usually characterized by two discriminating features. The propositions of physics assert something which might be false; they have a hypothetical character. On the contrary, since mathematical propositions are rules that condition the form of assertions, they remain immune from falsification. The propositions of physics refer to facts that may confirm or refute them. On the contrary, since mathematical propositions have no meaning independently of the demonstration procedures, it cannot be said that they refer to “facts” that pre-exist demonstrations. If we take a closer look, however, these two differences fade away. On the one hand, the propositions of physics are more resistant to experimental tests than has been said in the wake of logical positivism. On the other hand, the “factual” empirical material is defined and co-constituted by instruments whose arrangement is determined by the theory to be tested. I conclude by discussing the possibility of a Wittgensteinian philosophy of contemporary physics.

Toute science, admet-on, commence par détacher un objet en le rendant indépendant des sujets et des situations. Mais cette conception étroite de la connaissance scientifique laisse subsister des zones d'ombre. La conscience n'est pas un objet. Elle est ce sans quoi rien ne pourrait être pris pour objet. La conscience n'est pas détachable des sujets, car elle s'identifie à ce qui est vécu par un sujet. De façon analogue, en physique quantique, un phénomène n'est pas dissociable de son contexte expérimental, car il s'identifie à ce qui se manifeste à grande échelle au laboratoire. Que faire pour ne pas laisser ces cas extrêmes de côté? Généraliser la méthode scientifique. Ne plus la borner à définir et à caractériser des objets, mais l'étendre à la coordination directe des expériences. Telle est la révolution de pensée qu'il faut accomplir pour résoudre, ou plutôt dissoudre, deux questions-limites de la science : le problème de l'origine de la conscience et le paradoxe du "chat de Schrödinger" en physique quantique.

Les études que nous rassemblons ici font écho aux débats les plus récents sur la philosophie des mathématiques de Wittgenstein, qui est bien certainement l'aspect le plus controversé de son œuvre. Elles sont, pour l'essentiel, consacrées au statut et aux fonctions des preuves mathématiques et aux "réactions" du philosophe aux théorèmes de Gödel. C'est dire qu'elles tournent autour de l'anti-platonisme foncier de Wittgenstein en philosophie des mathématiques et de son refus catégorique de toute méta-mathématique. E. R.

Quel est le sens des théories physiques? Il fut une époque où le débat entre réalistes et anti-réalistes ne souffrait guère de nuances. Le réalisme scientifique était vide parce qu'il renvoyait à un ailleurs ou à un futur indéfinis ; l'anti-réalisme était aveuglé parce qu'il privait la recherche de but et de direction. Aujourd'hui, bien des réalistes ont appris à se défaire des équivalences rigides entre l'objectivité et la réalité, entre l'objet visé et la " cause " des phénomènes, entre l'invariant et l'en-soi, entre la pratique structurée de la recherche et la préexistence des structures. Et les anti-réalistes, qui adhéraient à la surface des " faits ", des opérations et des interactions sociales, n'ignorent plus les projets, les engagements et les valeurs. Ni les uns ni les autres ne se satisfont désormais d'un strict dualisme entre le donné et le construit. La voie s'en trouve dégagée pour une réappréciation des " étrangetés " de la mécanique quantique : elles ne témoigneraient pas de la distance excessive qui nous sépare du réel ; elles ne nous contraindraient pas davantage à l'agnosticisme. Elles sont peut-être le signe ambigu mais récurrent de l'aveuglante proximité du réel. Reprenant en partie certains de ses propres travaux de recherche, Michel Bitbol appuie ces orientations sur des études de cas concernant l'atomisme, le " vide quantique ", le hasard, la naissance des théories physiques du XXe siècle et le concept d' " état relatif ".

Context: We are presently witnessing a revival of introspective methods, which implicitly challenges an impressive list of in-principle objections that were addressed to introspection by various philosophers and by behaviorists. Problem: How can one overcome those objections and provide introspection with a secure basis? Results: A renewed definition of introspection as “enlargement of the field of attention and contact with re-enacted experience,” rather than “looking-within,” is formulated. This entails (i) an alternative status of introspective phenomena, which are no longer taken as revelations of some an sich slice of experience, but as full-fledged experiences; and (ii) an alternative view of the validity of first-person reports as “performative coherence” rather than correspondence. A preliminary empirical study of the self-assessed reliability of introspective data using the elicitation interview method is then carried out. It turns out that subjects make use of reproducible processual criteria in order to probe into the authenticity and completeness of their own introspective reports. Implications: Introspective inquiry is likely to have enough resources to “take care of itself.” Constructivist content: It is argued that the failure of the introspectionist wave of the turn of the 19th/20th centuries is mostly due to its unconditional acceptance of the representationalist theory of knowledge, and that alternative non-representationalist criteria of validity give new credibility to introspective knowledge.

Rovelli’s RQM is first characterized by contrast with both Everett’s and Bohr’s interpretations of quantum mechanics. Then, it is shown that a basic difficulty arises from the choice of formulating RQM in a naturalistic framework. Even though, according to Rovelli’s interpretation, statements about the world only make sense relative to certain naturalized observers described by means of quantum mechanics, this very meta-statement seems to make sense relative to a sort of super-observer which does not partake of the naturalized status of ordinary observers. The difficulty is solved by substituting functional reference frames for physical (or naturalized) observers throughout. Instead of being relative to physical observers, statements about the state vector of physical systems are here relative to well-defined projects of probabilistic prediction which may be embodied by several physical observers.

Context: In his work on neurophenomenology, the late Francisco Varela overtly tackled the well-known “hard problem” of the (physical) origin of phenomenal consciousness. Problem: Did he have a theory for solving this problem? No, he declared, only a “remedy.” Yet this declaration has been overlooked: Varela has been considered (successively or simultaneously) as an idealist, a dualist, or an identity theorist. Results: These primarily theoretical characterizations of Varela’s position are first shown to be incorrect. Then it is argued that there exists a stance (let’s call it the Varelian stance) in which the problem of the physical origin of primary consciousness, or pure experience, does not even arise. Implications: The nature of the “hard problem” of consciousness is changed from an intellectual puzzle to an existential option. Constructivist content: The role of ontological prejudice about what the world is made of (a prejudice that determines the very form of the “hard problem” as the issue of the origin of consciousness out of a pre-existing material organization) is downplayed, and methodologies and attitudes are put to the fore.

It is pointed out that the probabilistic character of a theory does not indicate by itself a distancing with respect to the norms of objectification. Instead, the very structure of the calculation of probabilities utilised by this theory is capable of bearing the trace of a constitution of objectivity in Kant’s sense. Accordingly, the procedure of the constitution of objectivity is first studied in standard and in quantum cases with due reference to modern cognitive science. Then, an examination of the differences between classical and quantum probabilities is performed. It is shown that the form of the quantum calculation of the probabilities carries the mark of the contextuality of the phenomena on which it bears. Conversely, certain conditions that have the form of Bell’s inequalities carry the mark of decontextualization.

There are two versions of the putative connection between consciousness and the measurement problem of quantum mechanics : consciousness as the cause of state vector reduction, and state vector reduction as the physical basis of consciousness. In this article, these controversial ideas are neither accepted uncritically, nor rejected from the outset in the name of some prejudice about objective knowledge. Instead, their origin is sought in our most cherished (but disputable) beliefs about the place of mind and consciousness in the world. It is first pointed out that these common beliefs about mind and consciousness arise from reification of situated first-person experience. Then, situatedness is shown to be a constitutive part of any exhaustive treatment of quantum measurements. It turns out that the alleged connection between consciousness and the measurement problem is a symptom of (i) the ineliminability of our being situated from the end-product of science, and (ii) our difficulty to express correctly this being situated.

In recent years, many philosophers of modern physics came to the conclusion that the problem of how objectivity is constituted (rather than merely given) can no longer be avoided, and therefore that a transcendental approach in the spirit of Kant is now philosophically relevant. The usual excuse for skipping this task is that the historical form given by Kant to transcendental epistemology has been challenged by Relativity and Quantum Physics. However, the true challenge is not to force modern physics into a rigidly construed static version of Kant's philosophy, but to provide Kant's method with flexibility and generality. In this book, the top specialists of the field pin down the methodological core of transcendental epistemology that must be used in order to throw light on the foundations of modern physics. First, the basic tools Kant used for his transcendental reading of Newtonian Mechanics are examined, and then early transcendental approaches of Relativistic and Quantum Physics are revisited. Transcendental procedures are also applied to contemporary physics, and this renewed transcendental interpretation is finally compared with structural realism and constructive empiricism. The book will be of interest to scientists, historians and philosophers who are involved in the foundational problems of modern physics