What is Quantum Field Theory? Idealisation, Explanation and Realism in High Energy Physics.

Quantum field theory (QFT) poses a challenge to the orthodox methodological framework of the philosophy of science. The first step of investigating a physical theory, it is commonly assumed, is to specify some mathematical structures which constitute its formalism. In the case of QFT however this is a highly non-trivial task. There are a variety of prima facie distinct formulations of the theory: most strikingly, there is a gulf between the axiomatic formulations of QFT developed by mathematical physicists and the formalisms employed in mainstream high energy physics. In recent years this has led to debate about which version of the theory those interested in the foundations of physics ought to be looking at. This thesis offers a response to this problem. I argue that we should abandon the search for a single canonical formulation of QFT and instead take a more pluralistic stance which allows that different strands of the QFT programme may be appropriate starting points for addressing different philosophical questions. The overarching claim of the thesis is that, while the axiomatic approach to QFT may be the right framework for addressing some internal question raised by the QFT programme, formulations of QFT which incorporate cutoffs on the allowed momentum states can express all of the claims that we have any reason to believe on the basis of the empirical successes of high energy physics. In the course of this discussion I offer new perspectives on foundational issues like the status of relativity and unitarily inequivalent representations in QFT. Furthermore, I suggest that QFT and high energy physics offer fruitful grounds for discussing broader issues in the philosophy of science, and in particular the challenge of formulating a viable version of scientific realism.