Federico Laudisa

According to a wrong interpretation of the Bell theorem, it has been repeatedly claimed in recent times that we are forced by experiments to drop any possible form of realism in the foundations of quantum mechanics. In this paper I defend the simple thesis according to which the above claim cannot be consistently supported: the Bell theorem does not concern realism, and realism per se cannot be refuted in itself by any quantum experiment. As a consequence, realism in quantum mechanics is not something that can be simply explained away once and for all on the basis of experiments, but rather something that must be conceptually characterized and discussed in terms of its foundational virtues and vices. To assess it, we cannot rely on experimentation but rather on philosophical discussion: realism is not a phlogiston-like notion, despite the efforts of the contemporary quantum orthodoxy to conceive it in Russellian terms as the relics of a bygone age.

The view that takes laws of nature to be essentially nothing more than descriptions of facts is still rather popular. The present article, on the contrary, defends the claim that the only real motivation for defending a descriptive view of laws—the quest for ontological parsimony—entails too high a price to pay in philosophical terms. It is argued that nomic primitivism, namely the alternative option that takes laws to be primitive fundamental entities in our ontology, is decisively more appealing, since it is the crucial role assigned to laws that makes a scientific theory of natural phenomena a system rather than a list. Finally, the implications that nomic primitivism might have for the issue of the status of the wave function in that particular formulation of quantum mechanics known as Bohmian mechanics are considered.

The Bell 1964 theorem states that nonlocality is a necessary feature of hidden variable theories that reproduce the statistical predictions of quantum mechanics. In view of the no-go theorems for non-contextual hidden variable theories already existing up to 1964, and due to Gleason and Bell, one is forced to acknowledge the contextual character of the hidden variable theory which the Bell 1964 theorem refers to. Both the mathematical and the physical justifications of this contextualism are reconsidered. Consequently, the role of contextualism in recent no-hidden-variables proofs and the import of these proofs are investigated. With reference to the physical intuition underlying contextualism, the possibility is considered whether a context-dependence of individual measurement results is compatible with context-independence of the statistics of measurement results

The papers collected in this volume are based on the best contributions to the conference of the Italian Society for Logic and Philosophy of Science (SILFS) that took place in Milan on 8-10 October 2007. The aim of the Society, since its foundation in 1952, has always been that of bringing together scholars - working in the broad areas of Logic, Philosophy of Science and History of Science - who share an open-minded approach to their disciplines and regard them as essentially requiring continuous confrontation and bridge-building to avoid the danger of over-specialism. In this perspective, logicians and philosophers of science should not indulge in inventing and cherishing their own "internal problems" - although these may occasionally be an opportunity for conceptual clarification - but should primarily look at the challenging conceptual and methodological questions that arise in any genuine attempt to extend our objective knowledge. As Ludovico Geymonat used to put it: " good] philosophy should be sought in the folds of science itself." Contributions are distributed into six sections, five of which - "Logic and Computing," "Physics and Mathematics," "Life Sciences," "Economics and Social Sciences," "Neuroscience and Philosophy of Mind" - are devoted to the discussion of cutting-edge problems that arise from current-day scientific research, while the remaining section on "General Philosophy of Science" is focused on foundational and methodological questions that are common to all areas.

It is usually held that the standard collapse model of a quantum measurement process grounds a kind of fundamental time asymmetry. The question whether and how it should be possible to reconstruct uniquely one's own history in an Everett no-collapse interpretation of quantum theory is investigated. A particular approach to the Everett interpretation, due to John S. Bell, is considered, according to which one of the chief claims of the Everett quantum theory is precisely that it allows us to do without the notion of history

The debate over the question whether quantum mechanics should be considered as a complete account of microphenomena has a long and deeply involved history, a turning point in which has been certainly the Einstein-Bohr debate, with the ensuing charge of incompleteness raised by the Einstein-Podolsky-Rosen argument. In quantum mechanics, physical systems can be prepared in pure states that nevertheless have in general positive dispersion for most physical quantities; hence in the EPR argument, the attention is focused on the question whether the account of the microphysical phenomena provided by quantum mechanics is to be regarded as an exhaustive description of the physical reality to which those phenomena are supposed to refer, a question to which Einstein himself answered in the negative. However, there is a mathematical side of the completeness issue in quantum mechanics, namely the question whether the kind of states with positive dispersion can be represented as a different, dispersion-free kind of states in a way consistent with the mathematical constraints of the quantum mechanical formalism. From this point of view, the other source of the completeness issue in quantum mechanics is the no hidden variables theorem formulated by John von Neumann in his celebrated book on the mathematical foundations of quantum mechanics, the preface of which already anticipates the program and the conclusion concerning the possibility of ‘neutralizing’ the statistical character of quantum mechanics

According to a wrong interpretation of the Bell theorem, it has been repeatedly claimed in recent times that we are forced by experiments to drop any possible form of realism in the foundations of quantum mechanics. In this paper I defend the simple thesis according to which the above claim cannot be consistently supported: the Bell theorem does not concern realism, and realism per se cannot be refuted in itself by any quantum experiment. As a consequence, realism in quantum mechanics is not something that can be simply explained away once and for all on the basis of experiments, but rather something that must be conceptually characterized and discussed in terms of its foundational virtues and vices. To assess it, we cannot rely on experimentation but rather on philosophical discussion: realism is not a phlogiston-like notion, despite the efforts of the contemporary quantum orthodoxy to conceive it in Russellian terms as the relics of a bygone age

The year 2005 has been named the World Year of Physics in recognition of the 100th anniversary of Albert Einstein's "Miracle Year," in which he published four landmark papers which had deep and great influence on the last and the current century: quantum theory, general relativity, and statistical mechanics. Despite the enormous importance that Einstein’s discoveries played in these theories, most physicists adopt a version of quantum theory which is incompatible with the idea that motivated Einstein in the first place. This seems to suggest that Einstein was fundamentally incapable of appreciating the `quantum revolution,’ and that his vision of physics as an attempt to reach a complete and comprehensive description of reality was ultimately impossible to obtain. Relativity theory has provided us with a picture of reality in which the world can be though as independent on who observes it, and the same can be said for statistical mechanics. Instead, quantum mechanics seems to suggest that physical objects do not exist `out there’ when someone is not observing them. In this framework, it is often suggested that any kind of causal explanation is impossible in the atomic and subatomic world, and therefore should be abandoned. This is why many think that it is in principle impossible for quantum theory to provide us with a coherent and comprehensive view of the world, in contrast with what happens with relativity and statistical mechanics. Is it really impossible to pursue Einstein’s ideal of physics also in the quantum framework? This book argues that this is not the case: the central idea is that Einstein’s vision of physics is still a live option, and indeed it is the one that best allows obtaining a unitary understanding of our physical theories. One can consider all the three theories mentioned above, suitably modified, as theories that are able to account and explain the world around us without too much departure from the classical framework. ------------------------------------------------------------------------------------------------------------------------------------------------------ La teoria della relatività, la meccanica statistica e la meccanica quantistica hanno profondamente rivoluzionato il nostro modo di concepire spazio, tempo, materia, probabilità e causalità, nonché il rapporto tra universo fisico ed osservatore, nozioni che sono state al centro della discussione filosofica dal mondo greco fino ai nostri giorni. Questo volume, opera di Valia Allori, Mauro Dorato, Federico Laudisa e Nino Zanghì, non solo intende suggerire nuovi metodi di confronto tra fisica e filosofia, ma prova altresì a rendere espliciti i presupposti filosofici che sono presenti nell'interpretazione che i fisici stessi danno del formalismo matematico.

The paper investigates the question whether the nature of non-locality in quantum mechanics can be better understood by viewing it as grounded in some sort of causation. A general conclusion that may be drawn from the discussion above is that, as far as ordinary quantum mechanics is concerned, we are facing a dilemma: either the notion of causation is interpreted in such general terms so as to lose sight of the original underlying intuition - so that we seem to do nothing but giving a different name to the puzzle under scrutiny - or we are led to ascribe to the special-relativistic spacetime structure a purely phenomenological status in order to make room for a preferred spacetime foliation, with respect to which causal relations can be univocally defined.

In the context of stochastic hidden variable theories, Howard has argued that the role of separability—spatially separated systems possess distinct real states—has been underestimated. Howard claims that separability is equivalent to Jarrett‘s completeness: this equivalence should imply that the Bell theorem forces us to give up either separability or locality. Howard's claim, however, is shown to be ill founded since it is based on an implausible assumption. The necessity of sharply distinguishing separability and locality is emphasized: a quantitative formulation of separability, due to D'Espagnat, is reviewed and found unsatisfactory, in that it basically conflates separability and locality in a single notion. Finally, the possibility of an ‘Einsteinian’ nonseparable realism, envisaged by Shimony, is reviewed and found also to be implausible

In recent years, a number of research projects have been proposed whose goal is to build large-scale simulations of brain mechanisms at unprecedented levels of biological accuracy. Here it is argued that the roles these simulations are expected to play in neuroscientific research go beyond the “synthetic method” extensively adopted in Artificial Intelligence and biorobotics. In addition we show that, over and above the common goal of simulating brain mechanisms, these projects pursue various modelling ambitions that can be sharply distinguished from one another, and that correspond to conceptually different interpretations of the notion of “biological accuracy”. They include the ambition to reach extremely deep levels in the mechanistic decomposition hierarchy, to simulate networks composed of extremely large numbers of neural units, to build systems able to generate rich behavioural repertoires, to simulate “complex” neuron models, to implement the “best” theories available on brain structure and function. Some questions will be raised concerning the significance of each of these modelling ambitions with respect to the various roles played by simulations in the study of the brain.

Relational quantum mechanics is an interpretation of quantum theory which discards the notions of absolute state of a system, absolute value of its physical quantities, or absolute event. The theory describes only the way systems affect each other in the course of physical interactions. State and physical quantities refer always to the interaction, or the relation, between two systems. Nevertheless, the theory is assumed to be complete. The physical content of quantum theory is understood as expressing the net of relations connecting all different physical systems