Why do we need vision? As it turns out, there are two answers to this question. On the one hand, we need vision to give us detailed knowledge of the world beyond ourselves, knowledge that allows us to recognize things from minute to minute and day to day. On the other hand, we also need vision to guide our actions in that world at the very moment they occur. These are two quite different job descriptions, and nature seems to have given us two different visual systems to carry them out. Dr. Goodale discusses how separate but interacting visual systems have evolved for the perception of objects on the one hand and the control of actions directed at those objects on the other, examining how both systems process information but each using the information in different ways.