  Consider a simple example: Suppose Lilian believes that a glass in front of her contains water, and this belief (together with her desires) causes her to reach for the glass. Her behavior is an instance of trying to get water, and it’s the instantiation of this property (and not, say, the property of being a certain kind of bodily motion) that we’re wondering about when we ask whether the intentional property of her belief is causally relevant.  (If our interest lay solely in explaining a particular bodily motion, we would rest content with a non-psychological, purely physiological explanation.) But now the answer seems straightforward. For what makes Lilian’s behavior a trying for water is that it’s caused by a belief whose content concerns water. Once we realize that the behavioral property of the effect is itself broad, its connection to the intentional mental property seems clear.