On a confusion about there being two types of consciousness.

Progress in the scientific study of consciousness has been impeded by several fundamental controversies. One pertains to a major divide between theories: sensory versus cognitive. Here, we argue that the key to resolving this controversy is to reevaluate the conceptual distinction proposed by Block in 1995 between phenomenal consciousness (P) and access consciousness (A). We propose that P and A should not be understood as two different types of consciousness, but as two necessary conditions for consciousness. We illustrate how this conceptual shift allows making substantial progress in answering several unresolved questions, such as the neural mechanisms and functions of consciousness, and the relationship between consciousness and attention. Our proposal motivates a selective unification across these different classes of theories.