Metaphysicians and cosmologists often make bold, surprising claims about the universe. It is bigger, older, full of more things, more intricately interconnected, than most of us ever thought. Supposing they are correct, does that have any bearing on what we ought to believe about everyday matters, and on what we ought to feel, want, and do in everyday contexts? Many philosophers have been explicitly or implicitly committed to answering 'no' to this question. In Living in a Strange World, Caspar Hare argues for 'yes'. If advocates of chaos theory are correct then we should rethink how we ought to feel about past evil actions. We ought to feel the positive analogue of regret towards almost everything that has ever been done. If advocates of plenitudinous material ontologies are correct, then we should rethink how we ought to feel about our own suffering versus the suffering of others, and what we ought to believe about where we are and who we are. If advocates of spatial and material infinity are correct then we should rethink how we ought to treat strangers. Whether and how we ought to help them depends in surprising ways on how much we know about them. In sum--bold claims in metaphysics and cosmology matter. Living in a Strange World explores what metaphysics and cosmology teach us about navigating the complexities of our existence and making thoughtful choices about how we live.