Integrated information theory is "a theory of consciousness that starts from the self-evident, essential properties (axioms) of experience and translates them into the necessary and sufficient conditions (postulates) for the PSC substrate of consciousness. The axioms are intrinsic existence (my experience exists from my own intrinsic perspective); composition (it has structure), information (it is specific), integration (it is unitary) and exclusion (it is definite). The corresponding postulates state that the physical substrate of an experience must have cause–effect power upon itself (intrinsic existence); its parts must have cause–effect power within the whole (composition); and the cause–effect power of the PSC must be specific (information), irreducible (integration) and maximally so (exclusion). The fundamental identity of IIT states that the quality or content of consciousness is identical to the form of the conceptual structure specified by the PSC, and the quantity or level of consciousness corresponds to its irreducibility (integrated information Φ)." - Tononi et al 2016, Nature Neuroscience Reviews