Is vision informationally encapsulated from cognition or is it cognitively penetrated? I shall argue that intentions penetrate vision in the experience of visual spatial constancy: the world appears to be spatially stable despite our frequent eye movements. I explicate the nature of this experience and critically examine and extend current neurobiological accounts of spatial constancy, emphasizing the central role of motor signals in computing such constancy. I then provide a stringent condition for failure of informational encapsulation that emphasizes a computational (...) condition for cognitive penetration: cognition must serve as an informational resource for visual computation. This requires proposals regarding semantic information transfer, a crucial issue in any model of informational encapsulation. I then argue that intention provides an informational resource for computation of visual spatial constancy. Hence, intention penetrates vision. (shrink)