Examining the philosophical foundations of theories in computational psychology, and cognitive science in general, is a methodology that is likely to yield strong results to problems in the philosophy of mind. O n e such problem is the problem of intentionality. A n intentional property is semantic: it has parts which refer or are true. T h e problem is to explain w h y these properties are empirically, and hence causally, respectable. A s in all special, "non-basic" sciences, an empirically respectable property has sufficient conditions for its instantiation. But specifying such conditions for the intentional properties used by computational psychology proves difficult, since apparently neither physical nor computational identity are enough. A solution is proposed by examining in some detail the computational theory of vision. A key element of this theory requires that the intentional properties attributed to representations are constrained by considering the later computational uses to which these representations must be put. This constraint is strong enough to yield sufficient conditions for a given representation to have a given intentional property. Since analogous constraints are likely to be found in other cognitive d o m a i n s , the result argued for constitutes an important methodological a n d philosophical insight about cognitive science in general.