||The causal theory of perception consists roughly of the claim that necessarily, if a subject S sees an object O, then O causes S to have a visual experience. Some have held that this claim is a conceptual truth. Thus, the idea is that in order to see an object, the object must be causally responsible for your visual experience. The causal theory of perception rules out certain problem cases as genuine instances of seeing: For instance, suppose that: (a) I seem to see a red ball at a certain distance and direction, (b) there is a red ball at precisely that distance and direction, but (c) unbeknownst to me, there is a mirror interposed between me and the red ball that reflects the image of a qualitative duplicate of the ball, and the reflection is what causes my visual experience. Here it seems wrong to say that I see the red ball behind the mirror. The causal theory of perception agrees with this judgment: Because the ball is not causally responsible for my experience, I do not see it.