Title: A Framework for Interpreting Physical Theories
Speaker: David Baker, Professor, Department of Philosophy, University of Michigan
It is delightful to go about interpreting physics, but troublesome to spell out exactly what we are doing when we go about it. For most interpretive purposes it isn’t necessary to spell this out too fully. One can quickly express a commitment to scientific realism, or to a form of anti-realism compatible with the substantiveness of the interpretive questions at play, and move on to the good stuff. But because our topic is symmetry and reality, we will have to go deeper into the foundations of interpretation before we move on. We are wondering what symmetries could be, in order to justify an argument from a symmetry’s existence to the unreality of non-invariant quantities. The possible justifications for such arguments will look very different depending on what it is for a quantity to be real. This leads pretty directly to a further problem about the practice of interpretation. The most credible accounts of what it is for something to be real depend on notions like fundamentality, naturalness or basic structure. But the theories most often interpreted by scholars in the foundations of physics are not fundamental, and in particular it’s extremely unlikely that these theories’ most basic quantities are the true fundamental building blocks. What it means to be realist about such theories, or to say that some of their structure is real, is one puzzle that needs addressing. More puzzling yet is the widespread practice of interpreting these theories as if they were fundamental. It’s sometimes suggested that this practice has created a house of cards, where large swathes of the literature can only teach us about counterfactual possibilities and not about the world we inhabit. In particular, some philosophers working on quantum field theory have reached the conclusion that interpreting a theory understood as effective must be a very different practice from interpreting it on the assumption that it’s exactly true. If this is right, much foundational work on physics has value (to the investigation of our world, at least) only as a source of useful analogies. Without denying the key insights of this work, I will defend a more optimistic view. The notions of approximate truth and of a theory’s domain of application are notions that no scientific realist can do without, even though they resist precise analysis with present-day conceptual resources. Taking these commitments as seriously as they deserve, an optimistic paradigm for interpretation appears tenable. On this paradigm, interpreting a theory on its own terms (i.e., on the fiction that it’s fundamental and exactly true) teaches us much about what is approximately true within its domain, in the actual world.