In this paper we introduce two dimensions over which current and recent theories of consciousness vary. Vehicle theories of consciousness propose that consciousness arises from some inherent property of mental representations or neural systems, irrespective of the computations they perform.
Process theories propose that consciousness arises as a result of a particular form of computation.
Specialized theories view consciousness as arising from dedicated machinery. We review and situate nine theories of consciousness in the 2x2 matrix generated by the two dimensions. We then examine some difficulties with the precise characterizations of these dimensions. Vehicle theories are those that place greater emphasis on implementation.