On a causal theory of rational behavior, behavior is just a causal consequence of the reasons an actor has. One of the difficulties with this theory has been the possibility of the "wayward causal chains," according to which reasons can cause the expected output, but in such an unusual way that the output is clearly not intentional. The inability to find a general way of excluding these wayward chains without implicitly appealing to elements incompatible with a pure causal account (like (...) brute acts of will) has been a problem for the causal theory. This essay attempts to find a general solution to the problem. The solution rests on the premise that behavior-producing systems are goal-directed, and that on a purely causal analysis of goal-directedness it can be shown that the wayward chains' resulting in the goal is purely fortuitous because these chains do not subserve the function of the system. (shrink)