Once upon a time, people thought that all perception was conscious. Indeed, it was widely believed that all mental states are conscious, so the problem of explaining consciousness collapses into the problem of explaining mentality. But things have changed. Most people now believe that a lot goes on unconsciously. Indeed, some people believe that mental states that are not perceptual in nature are never conscious. That’s a matter of controversy. Less controversial is the claim that perceptual states are conscious some (...) of the time, but not all of the time. This raises a question. When are perceptual states conscious? A theory of consciousness is, in large part, an answer to that question. In this chapter, I will offer a few critical remarks on one answer that has been popular in philosophy, and then I will offer a defense of another answer that has emerged out of cognitive science. To avoid undue suspense, the answer that I favor is that perceptual states become conscious when and only when the perceiver is attending. (shrink)