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Quantum mechanics according to a pragmatist transcendental approach: study of the universal or relative nature of the means of knowledge in microphysics

Final Activity Report Summary - QMAPTA (Quantum mechanics according to a pragmatist transcendental approach: study of the universal or relative nature of the means of knowledge in microphysics)

This research aimed at clarifying the origins, the status and the role of the various means of knowledge used in the research activity of microphysics. The objective was to determine, for each of them, if it is universal (i.e. valid and relevant in the context of every possible research activity) or relative to a specific research activity (the one of microphysics).

The first means of knowledge examined were the instrumental ones, that is, the measurement apparatus. At first glance, it seems that every measurement apparatus always yields a well-defined outcome, as if this was a universal feature. Nevertheless, the quantum measurement problem implies that a measurement in general never ends up with a well-defined outcome. Based on a detailed analysis of this problem, I pointed out that it arises only within the frame of the "standard" interpretation of quantum mechanics. Therefore, the question of the universality of the determinateness or indeterminateness of the measurement outcome remains dependent on the endorsed interpretation.

Another common idea is that all measurement outcomes, even in microphysics, are "classical" because they are expressed by means of the concepts of classical physics. I analysed Bohr's arguments in favour of this idea and came to the conclusion that they are failing. Nevertheless, I pointed out that the concepts which are actually used for the description of the measurement outcomes in microphysics originate from classical physics and the scales associated to the measured observables are extensions of the ones of the classical physical magnitudes. They can thus be considered as "classical" by reference to classical physics only in a narrow sense.

The second means of knowledge examined were the conceptual means enabling us to perceive the measurement outcomes and to refer to them. According to Kant, space (as well as time) is an a priori condition, and hence, universal means for this purpose. I analysed his view in the light of physical, psychological and philosophical considerations and came to the conclusion that space, whatever its structure, is indeed an a priori condition of any empirical knowledge. However, I argued that the specific structure being assigned to space is contingent and dependent on the research activity under consideration.

Finally, the research focused on the theoretical means of knowledge, and more specifically on the central notion of "atom". I reconsidered the debate on this notion between Boltzmann and Mach at the end of the 19th century. Against the common negative assessment of Mach's anti-realist view, the analysis of his different arguments led me to support that some of them (the epistemological ones) are still today of great relevance. The notion of atom, I argued, makes it possible to refer synthetically to a whole set of phenomena. In regard of this usefulness for any scientific practice in physics, the notion of atom can be considered as universal.