ABSTRACT
Integrated information theory (IIT), developed by Giulio Tononi and colleagues, aims to provide a theory of consciousness with explanatory, predictive, and inferential power, starting from phenomenology itself. IIT contrasts with current approaches that start from the neural correlates of consciousness (NCC) with the hope of identifying generalized principles about the nature of consciousness. Instead, IIT first identifies the essential properties of every experience from consciousness itself. From these “axioms” of phenomenology, IIT then infers a set of requirements (“postulates”) for a physical system to be a substrate of consciousness, while the NCC serve as empirical data for evaluating IIT’s predictions. In particular, IIT predicts that the quality or content of an experience is structurally identical to the cause-effect structure of its physical substrate, and that the quantity or level of consciousness corresponds to the amount of intrinsic cause-effect power the substrate has onto itself. IIT, moreover, offers a theoretical formalism that, in principle, makes it possible to evaluate whether a physical system complies with the IIT postulates and thus forms a physical substrate of consciousness, to quantify the level of consciousness of such a system, and to provide a full account of its phenomenological structure in causal terms.
