Things, Structures and Phenomena in Quantum Physics

Armond Duwell

Michel Bitbol

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 (a byproduct of Kant’s transcendental idealism) 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 (1909-1980). 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.

Robert P Crease

Scientific inquiry takes place inside large organizational structures that can be thought of as a series of loosely connected ‘workshops,’ carefully supervised and regulated environments in which special things—quantum phenomena, for instance—can be made to show themselves for study and measurement. Each workshop involves ‘frames,’ or sets of assumptions and concepts that define the physical system under study. Philosophers inquire into workshop activity mainly through three general approaches.

Philippe Grangier

Patrick A. Heelan

Heelan argues that the philosophy of complementarity, although successful in providing physicists with a common language with which to describe quantum phenomena, also contains a theory about scientific method and about human knowing which is open to criticism. Heelan here criticises the following points arising out of the philosophy of complementarity: psycho-physical parallelism; the view that quantum mechanical properties are to be defined classically; and the perturbation theory of measurement. In the course of the criticism, he elaborates the distinction between two types of concepts with different logical structures; viz., operational or observational concepts which state a similarity between things judged on the basis of appearance or utility to us, and explanatory concepts which state a similarity between things judged on the basis of a self-defining set of different relations between things. Heelan thus shows how a physical concept is definable by any appropriate measuring-process. The description of the measuring­process and, hence, the definition of the physical property involve the two classes of concepts described above, but in different ways. Thus one may regard the Indeterminacy Relations, not as stating limi­tations of our knowledge, but as describing more exactly the behaviour of individual systems.