English: Axioms and postulates of integrated information theory (IIT). The illustration is a colourized version of Ernst Mach's ‘View from the left eye’

(i) Intrinsic existence

Consciousness exists: my experience just is. Indeed, that my experience here and now exists—it is real or actual—is the only fact I am immediately and absolutely sure of, as Descartes realized four centuries ago. Moreover, my experience exists from its own intrinsic perspective, independent of external observers.

(ii) Composition

Consciousness is structured: each experience is composed of many phenomenological distinctions, elementary or higher order, which also exist. Within the same experience, for example, I may distinguish a book, a blue colour, a blue book and so on.

(iii) Information

Consciousness is specific: each experience is the particular way it is—it is composed of a specific set of specific phenomenal distinctions—thereby differing from other possible experiences (differentiation). Thus, an experience of pure darkness and silence is what it is because, among other things, it is not filled with light and sound, colours and shapes, there are no books, no blue books and so on. And being that way, it necessarily differs from a large number of alternative experiences I could have. Just consider all the frames of all possible movies: the associated visual percepts are but a small subset of all possible experiences.

(iv) Integration

Consciousness is unified: each experience is irreducible to non-interdependent subsets of phenomenal distinctions. Thus, I experience a whole visual scene, not the left side of the visual field independent of the right side (and vice versa). For example, the experience of seeing written in the middle of a blank page the word ‘HONEYMOON’ is irreducible to an experience of seeing ‘HONEY’ on the left plus the experience of seeing ‘MOON’ on the right. Similarly, seeing a blue book is irreducible to seeing a grey book plus the disembodied colour blue.

(v) Exclusion

Consciousness is definite, in content and spatio-temporal grain: each experience has the set of phenomenal distinctions it has, neither less (a subset) nor more (a superset), and it flows at the speed it flows, neither faster nor slower. Thus, the experience I am having is of seeing a body on a bed in a bedroom, a bookcase with books, one of which is a blue book, but I am not having an experience with less content—say, one lacking the phenomenal distinction blue/not blue, or coloured/not coloured; nor am I having an experience with more content—say, one endowed with the additional phenomenal distinction high/low blood pressure. Similarly, my experience flows at a particular speed—each experience encompassing a hundred milliseconds or so—but I am not having experience that encompasses just a few milliseconds or instead minutes or hours.