What do we see when we look at someone's expression of fear? I argue that one of the things that we see is fear itself. I support this view by developing a theory of affect perception. The theory involves two claims. One is that expressions are patterns of facial changes that carry information about affects. The other is that the visual system extracts and processes such information. In particular, I argue that the visual system functions to detect the affects of others when they are expressed in the face. I develop my theory by drawing on empirical data from psychology and brain science. Finally, I outline a theory of the semantics of affect perception.