Table 2.

Integrated Information Theory (IIT) axioms and postulates, with corresponding examples of experiences and mechanistic systems.

IIT axioms: Essential properties of experience	Example experiences	IIT postulates: Properties of physical systems capable of accounting for experience	Example systems
Intrinsic existence:
Experience exists from its own intrinsic perspective (i.e., subjectivity), independent of external observers.	My experience of a red apple has intrinsic existence in that it is both real to me and also private.	A system has cause–effect power upon itself; present states must inform probabilities of past and future states, so linking causes and effects.	A brain has internal connectivity that influences which states are likely to flow from the past to the future, given its present state; some parts of brains have more intrinsic connectivity than others.
Composition:
Experience is structured by the elementary or higher-order subjective distinctions out of which it is composed.	My experience of a red apple is composed of particular features, such as redness for color and apple shape for form.	A system is structured by the more elementary sub-systems out of which it is composed, and which have cause–effect power upon the system.	A brain is composed of neurons, whose particular configurations influence its past and future states; different parts of brains have different compositions.
Information:
Experience is particular in being composed of a specific set of subjective distinctions, so being differentiated from other possible experiences.	My experience of a red apple is informative in being perceived in terms of particular qualities of subjective redness (as opposed to greenness) and apple shape (as opposed to pear shape).	A system specifies a particular cause–effect structure that informs particular probabilistic repertoires of past causes and future effects for the system and sub-systems, so differentiating particular states from other possible states.	A brain can be configured in many different ways, and so any particular configuration is highly informative in terms of being distinguished from other possible configurations; some parts of brains are more informative than others in different contexts.
Integration:
Each experience is unified in being irreducible to independent subsets of subjective distinctions.	My experience of a red apple is integrated in that redness and apple shape are not independently perceived, but are instead combined into a unified whole.	A system specifies a unified cause–effect structure that is irreducible to independent sub-systems (phi > 0), including its minimally interdependent component.	A brain has properties that do not exist in its individual neurons considered separately; some parts of brains are more integrated than others in different contexts.
Exclusion:
Each experience is definite in content and spatiotemporal grain, specifying a particular set of subjective distinctions unfolding on particular spatiotemporal scales.	My experience of a red apple has particular contents with respect to space and time, with particular redness and apple shape being perceived at some spatiotemporal scales and not others.	A system specifies particular cause-effect repertoires over particular sets of elements at particular spatial and temporal grains. The boundaries of a system are defined by a complex entailing a maximally irreducible conceptual structure (MICS) existing at particular spatial and temporal grains, whose total integrated information is quantified as Phi-max.	A brain and its sub-systems have particular boundaries that determine the extent to which they function as integrative wholes in space and time; some parts of brains have clearer boundaries than others in different contexts (e.g., modularity).