Sean Carroll (California Institute of Technology)
We often think of fundamental theories in terms of spatial scales: the smaller the elements of a theory's ontology, the more fundamental it must be. I will argue that it's better to think in terms of comprehensiveness: the more fundamental a theory is, the wider is its domain of applicability in accurately modeling the world. From this perspective, the fact that theories are hierarchical is not a necessary feature - two theories could, in principle, be applicable in overlapping domains without one being a subset of another - and the fact that theories often are is an interesting feature of the real world. I will briefly discuss why properties of quantum gravity implies that quantum field theory is probably not fundamental, and how quantum mechanics more generally could nevertheless be
