The physics and metaphysics of quantum field theory

Abstract

Apart from being a long-standing interest for all sorts of philosophers for two millennia, ontology also appears to be very much involved in the development of modern and contemporary scientific theories. In our times, the ban on ontology— which was a heritage of (some, not all, of) the logical empiricists—belongs to the very history of philosophy of science: as a matter of fact, it is just contemporary physics, the so-called queen of the sciences, that forces us to re-examine fundamental ontological intuitions and to assess whether and to what extent those intuitions are compatible with the conceptual content of fundamental physical theories. It is now more than a century that quantum mechanics (QM) represents a puzzle for all who strive for a philosophically sound image of the physical world. In fact, the controversy concerns not only the details of the several interpretations of the quantum formalism but also the very task of the theory: according to some, the theory is simply a set of recipes that enable physicists to handle the experimental evidence, whilst according to others, there is nothing in the theory that prevents it from trying to describe the world in a realistic and objective (namely, observer-free in principle) way. Since one of the major issues in the foregoing controversies concerns the potential tension between ordinary QM and relativity theory generated by non-locality, a growing number of philosophers and physicists alike have begun, more recently, to wonder whether any light might be shed by shifting to the level of the so-called second quantization; a shift also driven by the intuition that if there is to be some sort of unified physical worldview, this should incorporate not simply non-relativistic QM but quantum field theory (QFT), viz., the theory that in one way or another should be the basis of all theoretical physics. In addition to that, QFT appears to raise questions—concerning identity, localizability and the like—for which contemporary analytical ontology claims to have some useful toolkits.