Although our mental lives involve many conscious states, it is generally recognized that many mental states also occur without being conscious. The difference has to do with whether we are, in some way or other, conscious of the states in question. If one is in no way whatever conscious of a mental state, we do not count that state as being conscious, at least not as we intuitively draw the commonsense distinction between conscious and nonconscious states. It is another question just how we are conscious of those states we do count as conscious, a question that has often divided theorists and to which I will shortly turn. But if one is not at all conscious of a state, that state is not a conscious state.

Rosenthal, D. M. (2000). Consciousness, Content, and Metacognitive Judgments. Consciousness and Cognition, 214, p. 203. doi:10.1006/ccog.2000.0437