ABSTRACT
Time travel is a staple of contemporary science fiction, and the philosophically puzzling features of time travel are precisely those features that make for the most interesting science fiction stories. Nothing in contemporary physics seems to rule out the possibility of time travel. Nevertheless, many have thought that metaphysical considerations do. This chapter explores the most important philosophical problems about time travel. The idea that presentism is inconsistent with time travel is intuitively quite compelling. David Lewis solves the paradox by denying that only one of the claims can be true. According to Lewis, ability claims are context-sensitive. Relative to what people know about Clare’s abilities, equipment, and other conditions, Clare can kill her grandfather. Causal loops are deeply puzzling; many think that they are impossible. Time travel stories that incorporate causal loops are ubiquitous; and, though some are manifestly incoherent, not nearly all of them strike people this way.
