Abstract
Philosophers in the Western tradition have both theorized about imagination and used imagination in their theorizing about other matters. In this chapter, I first provide a brief overview of philosophical theorizing about imagination with a special focus on its relation to other mental states such as belief and perception. I then turn to a discussion of the methodological role that imagination has played in philosophy. I here focus on the imaginability principle, i.e., the claim that the imaginability of a given scenario entails that such a scenario is in some sense possible. Relying on this kind of principle, philosophers have used imagination to justify theories in domains such as philosophy of mind, metaphysics and ethics.