Humans can think about things and events in the external world, including some that are very remote. We have beliefs about Pluto, couches, the weather, and our moral obligations, to name a few. This is a remarkable fact, and philosophers have raised a number of questions about it. What does it take to be able to represent objects and events? Can computers or other machines have this capacity? Can we have a science of representation, in the same way as we have, for example, a science of the brain? This course will address these and related questions, focusing on contemporary work in philosophy, cognitive science, and linguistics.