We all think we know what matter is, even if we don't know the details of contemporary physics, and we assume that materialism is an ancient and clearly-defined view whose main alternative is dualism. In fact, however, the history of the concept of matter takes a number of surprising twists and turns, and through much of that history, materialism would have seemed not only unattractive but downright incoherent. This talk will present a whirlwind tour of this history of the concept of matter in Western natural philosophy from ancient Greece to the 19th century.Steven Horst is Professor of Philosophy at Wesleyan, and author of Symbols, Computation and Intentionality (1996), Beyond Reduction (2007), Laws, Mind, and Free Will (2011), and Cognitive Pluralism (in press).