The heuristic value of Pylyshyn's cognitive impenetrability theory is questioned in this commentary, mainly because, as it stands, the key argument cannot be challenged empirically. Pylyshyn requires unambiguous evidence for an effect of cognitive states on early perceptual mechanisms, which is impossible to provide because we can only infer what might happen at these earlier levels of processing on the basis of evidence collected at the post-perceptual stage. Furthermore, the theory that early visual processes cannot be modified by cognitive states implies that it is totally pointless to try to investigate interactions between consciousness and neurosensory processes.