 The second question mentioned above is a question about whether time itself—as opposed to just some particular feature of time, like time’s arrow—might merely be an emergent feature of the world. This question has become especially pressing as philosophers of physics have turned their attention to theories of quantum gravity in which there does not seem to be anything like temporal structure at the fundamental level. Work in this area is nascent, but some of the questions of interest include: Does quantum gravity eliminate time entirely or does it merely make time a non-fundamental feature of the world? What would it mean for something temporal to be grounded in something atemporal and what sort of grounding relation would be involved? What is the distinction between causal structure (especially the causal structure in causal set theory—one approach to quantum gravity) and temporal structure? And how can a theory that eliminates time entirely be empirically confirmed or disconfirmed?