 But what does it mean to say that introspection is like perception? In what respects? As Shoemaker (1994a, 1994b, 1994c) points out, in a number of respects introspection is plausibly unlike perception. For example, introspection does not involve a dedicated organ like the eye or ear (though as Armstrong 1968 notes, neither does bodily proprioception). Both friends and foes of self-detection accounts have tended to agree that introspection does not involve a distinctive phenomenology of “introspective appearances” (Shoemaker 1994a, 1994b, 1994c; Lycan 1996; Rosenthal 2001; Siewert 2012): The visual experience of redness has a distinctive sensory quality or phenomenology that would be difficult or impossible to convey to a blind person; analogously for the olfactory experience of smelling a banana, the auditory experience of hearing a pipe organ, the experience of touching something painfully hot. To be analogous to sensory experience in this respect, introspection would have to generate an analogously distinctive phenomenology—some quasi-sensory phenomenology in addition to, say, the visual phenomenology of seeing red that is the phenomenology of the introspective appearance of the visual phenomenology of seeing red. This would seem to require two layers of appearance in introspectively attended sensory perception: a visual appearance of the outward object and an introspective appearance of that visual appearance. (This isn’t to say, however, that introspection, or at least conscious introspection, doesn’t involve some sort of “cognitive phenomenology”—if there is such a thing—of the sort that accompanies conscious thoughts in general: See Bayne and Montague, eds., 2011.)