Federico Laudisa

Non-local realistic theories and the scope of the Bell theorem

According to a widespread view, the Bell theorem establishes the untenability of so-called ‘local realism’. On the basis of this view, recent proposals by Leggett, Zeilinger and others have been developed according to which it can be proved that even some non-local realistic theories have to be ruled out. As a consequence, within this view the Bell theorem allows one to establish that no reasonable form of realism, be it local or non-local, can be made compatible with the (experimentally tested) predictions of quantum mechanics. In the present paper it is argued that the Bell theorem has demonstrably nothing to do with the ‘realism’ as defined by these authors and that, as a consequence, their conclusions about the foundational significance of the Bell theorem are unjustified.

Against the ‘no-go’ philosophy of quantum mechanics

In the area of the foundations of quantum mechanics a true industry appears to have developed in the last decades, with the aim of proving as many results as possible concerning what there cannot be in the quantum realm. In principle, the significance of proving ‘no-go’ results should consist in clarifying the fundamental structure of the theory, by pointing out a class of basic constraints that the theory itself is supposed to satisfy. In the present paper I will discuss some more recent no-go claims and I will argue against the deep significance of these results, with a two-fold strategy. First, I will consider three results concerning respectively local realism, quantum covariance and predictive power in quantum mechanics, and I will try to show how controversial the main conditions of the negative theorem turn out to be—something that strongly undermines the general relevance of these theorems. Second, I will try to discuss what I take to be a common feature of these theoretical enterprises, namely that of aiming at establishing negative results for quantum mechanics in absence of a deeper understanding of the overall ontological content and structure of the theory. I will argue that the only way toward such an understanding may be to cast in advance the problems in a clear and well-defined interpretational framework—which in my view means primarily to specify the ontology that quantum theory is supposed to be about—and after to wonder whether problems that seemed worth pursuing still are so in the framework.

Model testing, prediction and experimental protocols in neuroscience: a case study.

In their theoretical and experimental reflections on the capacities and behaviours of living systems, neuroscientists often formulate generalizations about the behaviour of neural circuits. These generalizations are highly idealized, as they omit reference to the myriads of conditions that could perturb the behaviour of the modelled system in real-world settings. This article analyses an experimental investigation of the behaviour of place cells in the rat hippocampus, in which highly idealized generalizations were tested by comparing predictions flowing from them with real-world experimental results. The aim of the article is to identify (1) under what conditions even single prediction failures regarding the behaviour of single cells sufficed to reject highly idealized generalizations, and (2) under what conditions prima facie counter-examples were deemed to be irrelevant to the testing of highly idealized generalizations. The results of this analysis may contribute to understanding how idealized models are tested experimentally in neuroscience and used to make reliable predictions concerning living systems in real-world settings.

Box-and-arrow explanations need not be more abstract than neuroscientific mechanism descriptions

The nature of the relationship between box-and-arrow (BA) explanations and neuroscientific mechanism descriptions (NMDs) is a key foundational issue for cognitive science. In this article we attempt to identify the nature of the constraints imposed by BA explanations on the formulation of NMDs. On the basis of a case study about motor control, we argue that BA explanations and NMDs both identify regularities that hold in the system, and that these regularities place constraints on the formulation of NMDs from BA analyses, and vice versa. The regularities identified in the two kinds of explanation play a crucial role in reasoning about the relationship between them, and in justifying the use of neuroscientific experimental techniques for the empirical testing of BA analyses of behavior. In addition, we make claims concerning the similarities and differences between BA analyses and NMDs. First, we argue that both types of explanation describe mechanisms. Second, we propose that they differ in terms of the theoretical vocabulary used to denote the entities and properties involved in the mechanism and engaging in regular, mutual interactions. On the contrary, the notion of abstractness, defined as omission of detail, does not help to distinguish BA analyses from NMDs: there is a sense in which BA analyses are more detailed than NMDs. In relation to this, we also focus on the nature of the extra detail included in NMDs and missing from BA analyses, arguing that such detail does not always concern how the system works. Finally, we propose reasons for doubting that BA analyses, unlike NMDs, may be considered “mechanism sketches.” We have developed these views by critically analyzing recent claims in the philosophical literature regarding the foundations of cognitive science.

The Uninvited Guest: ‘Local Realism’ and the Bell Theorem

The Western philosophical thought has learnt since its very early days that the idea that there is a world out there – a world whose properties are (at least partially) independent from what we might think of them and even from our very attempts to have access to them – has a peculiar status. Although for some the idea of a world out there is too obviously right in order to waste time to argue in favour of it, whereas for others it is too obviously wrong in order to waste time to try to refute it, most philosophers would agree that a more or less sophisticated array of arguments is needed in order to make realism (or anti-realism, or any variant that lies in the continuum between these two poles) a plausible position. This long and honoured story, however, seems to be forgotten when considered from the standpoint of the foundations of contemporary physics. Surprisingly enough, the world-out-there-idea has recently acquired to the eyes of many physicists and philosophers of physics the status of a pathology, to be recognized as such and to be eradicated as soon as possible.

Non-Locality and Theories of Causation

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.

Large-scale simulations of brain mechanisms: beyond the synthetic method

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 (i) to reach extremely deep levels in the mechanistic decomposition hierarchy, (ii) to simulate networks composed of extremely large numbers of neural units, (iii) to build systems able to generate rich behavioural repertoires, (iv) to simulate “complex” neuron models, (v) 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.

From Metaphysics to Physics and Back: the Example of Causation

The notion of causation seems especially apt for being a crossroad between physics and metaphysics, in view of a revived interest both for causal notions in general philosophical analysis in general and causal views of quantum mechanics. As far as the latter is concerned, interesting sort of questions naturally arise when the relation between nonlocality and causation is taken into account. Also on the basis of recent classifications of theories of causation, in the paper I first will draw some general remarks mainly of a methodological character, and I will then review the conditions under which nonlocality can be shown to seriously challenge the no-action-at-a-distance requirement that special-relativistic theories are usually thought to embody. In this connection I will turn then to recent work on causal models of EPR. Over and above the specific merits of these models – mainly concerning the refutation of ‘impossibility claims’ about causal models of quantum correlations – a question arises: what sort of conceptual advantage do we obtain in producing causal models for such correlations in absence of a deeper understanding of the overall structure of the theory? I will argue that the only way toward such an understanding may be to cast in advance the problems in a clear and well-defined interpretational framework – which means primarily to specify the ontology that quantum theory is supposed to be about – and after to wonder whether problems that seemed worth pursuing still are so in the framework.