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Bernard d'Espagnat

Publications and source records attributed to Bernard d'Espagnat.

7 recordsLinked to original sources

Quantum Physics and Reality

Contrary to classical physics, which was strongly objective i.e. could be interpreted as a description of mind-independent reality, standard quantum mechanics (SQM) is only weakly objective, that is to say, its statements, though intersubjectively valid, still merely refer to operations of the mind. Essentially, in fact, they are predictive of observations. On the view that SQM is universal conventional realism is thereby refuted. It is shown however that this does not rule out a broader form of realism, called here 'open realism', restoring the notion of mind-independent reality.

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Consciousness and the Wigner's friend problem

It is generally agreed that decoherence theory is, if not a complete answer, at least a great step forward towards a solution of the quantum measurement problem. It is shown here however that in the cases in which a sentient being is explicitly assumed to take cognizance of the outcome the reasons we have for judging this way are not totally consistent, so that the question has to be considered anew. It is pointed out that the way the Broglie-Bohm model solves the riddle suggests a possible clue, consisting in assuming that even very simple systems may have some sort of a proto-consciousness, but that their ``internal states of consciousness'' are not predictive. It is, next, easily shown that if we imagine the systems get larger, in virtue of decoherence their internal states of consciousness progressively gain in predictive value. So that, for macro-systems, they may be identified (in practice) with the predictive states of consciousness on which we ground our observational predictions. The possibilities of carrying over this idea to standard quantum mechanics are then investigated. Conditions of conceptual consistency are considered and found rather strict, and, finally, two solutions emerge, differing conceptually very much from one another but in both of which the, possibly non-predictive, generalized internal states of consciousness play a crucial role.

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A tentative new approach to the Schrödinger cat problem

Though scientifically unconvincing, the Broglie-Bohm model has the virtue of reproducing the observational predictions of quantum mechanics while being conceptually crystal-clear. Hence, even if we do not believe in it, we may find it useful in suggesting ways of removing conceptual difficulties. This procedure is here applied to the Schrödinger cat riddle (in its Wigner version). The outcome yields tentative views on the relationship between mentality and physical reality.

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Reply to K A Kirkpatrick

This is a reply to an article with the same title in which Kirkpatrick claimed that the considerations I put forward some thirty years ago on quantum mixtures are incorrect. It is shown here that Kirkpatrick's reasoning is erroneous.

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A note on measurement

Grounded on the quantum measurement riddle, a general argument against the universal validity of the superposition principle was recently put forward by Bassi and Ghirardi. It is pointed out that this argument is valid only within the realm of the philosophy of ``objectivistic realism'' which is not a necessary part of the foundations of physics, and that recent developments including decoherence theory do account for the appearance of macroscopic objects without resorting to a break of the principle.

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Quantum Theory : A Pointer To An Independent Reality

While philosophy of science is the study of problems of knowledge concerning science in general, there also exists - or should exist - a '' philosophy in science'' directed at finding out in what ways our actual scientific knowledge may validly contribute to the basic philosophical quest. Contrary to philosophy of science, which is a subject for philosophers, philosophy in science calls on the services of physicists. When, in its spirit, quantum theory and Bell's theorem are used as touchstones, the two main traditional philosophical approaches, realism and idealism, are found wanting. A more suitable conception seems to be an intermediate one, in which the mere postulated existence of a holistic and hardly knowable Mind-Independent Reality is found to have an explaining power. Some corrections to comments by Schins of a previous work on the same subject are incorporated.

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