Neural theories of consciousness come in many forms, though most in some way concern the so called “neural correlates of consciousness” or NCCs. Unless one is a dualist or other non-physicalist, more than mere correlation is required; at least some NCCs must be the essential substrates of consciousness. An explanatory neural theory needs to explain why or how the relevant correlations exist, and if the theory is committed to physicalism that will require showing how the underlying neural substrates could be identical with their neural correlates or at least realize them by satisfying the required roles or conditions (Metzinger 2000).