Teleological explanations are said to be forward looking. We ask why Lauren is walking and are told her purpose, which is to buy ice cream when she gets to the shop. Or we ask why vertebrates have kidneys and are told their function, which is filtering blood. In both cases, the end explains the means; something at a time is explained by something else at a later time. This inverts the usual order of causal explanations: If Johnny's throwing the ball explains the window breaking, his throwing preceded the breaking.

Purposive Explanations

How does Lauren's purpose explain her walking? Many philosophers would now say that the relation between her purpose and her walking is a special instance of ordinary physical causation. On a standard version of physicalism, an agent's purpose consists of beliefs and desires, which involve brain states that represent what is believed and desired...