In De anima III.2, Aristotle speaks of “perceiving that we are seeing and hearing”, which is usually interpreted as some form of reflexive awareness. This reflexive awareness has been interpreted either as a type of content which is part of every act of first-order perception (Caston), or as a type of content which is supplied by second-order perception that accompanies first-order perception (Kahn, Johansen). In this paper I argue for the latter view by emphasizing that reflexive awareness crucially involves awareness not only of the activity of the special senses, but also of their inactivity. I show why awareness of inactivity of one’s senses is of vital importance for animals and I adduce evidence that Aristotle was alert to that fact. I ascribe reflexive awareness to the common sense and propose that the common sense is always active in the waking state, continually registering the incoming motions from all the different sensory channels, but also registering omission of incoming motions from particular sensory channels. Thus, we perceive that we are seeing and hearing, but also that we are not seeing or hearing, when it so happens. This presents us with two different cases: that of the co-occurrence of both tokens, and that of the occurrence of a token of second-order perception without a token of first-order perception. Moreover, I show that the common sense is inactive in sleep, which causes simultaneous inactivity of the special senses, too. So, in sleep we are not seeing and hearing anything, but we do not perceive that we are not seeing and hearing. Because no monitoring takes place in sleep, we are unaware of the fact that our senses are not exercised by external objects, which is one of the conditions for being deceived by dreams, since dreamers tend to take dreams to be perceptions of real things. So, sleep gives us the case of non-occurrence of both tokens. The remaining permutation is the case of the occurrence of a token of first-order perception without a token of second-order perception, which I suggest is exemplified by excessive stimuli coming from one sense and impeding the stimuli arriving from another sense.