This paper presents Integrated Information Theory (IIT) 3.0, an advanced framework for understanding consciousness. IIT starts from phenomenological axioms: existence, composition, information, integration, and exclusion, which are formalized into postulates that specify how physical mechanisms must be configured to generate experience. These postulates define intrinsic information as "differences that make a difference" and integrated information as information specified by a whole that cannot be reduced to its parts. By applying these postulates at both the individual mechanism and system levels, IIT arrives at the identity that an experience is a maximally irreducible conceptual structure (MICS) and the set of elements generating it constitutes a complex. IIT predicts that a MICS specifies the quality of an experience and integrated information ΦMax specifies its quantity. Key results include the condensation of systems into major and minor complexes, the indirect relation of concepts to the external environment, the influence of anatomical connectivity on complexes, and the possibility of true "zombies" - unconscious feed-forward systems functionally equivalent to conscious complexes.This paper presents Integrated Information Theory (IIT) 3.0, an advanced framework for understanding consciousness. IIT starts from phenomenological axioms: existence, composition, information, integration, and exclusion, which are formalized into postulates that specify how physical mechanisms must be configured to generate experience. These postulates define intrinsic information as "differences that make a difference" and integrated information as information specified by a whole that cannot be reduced to its parts. By applying these postulates at both the individual mechanism and system levels, IIT arrives at the identity that an experience is a maximally irreducible conceptual structure (MICS) and the set of elements generating it constitutes a complex. IIT predicts that a MICS specifies the quality of an experience and integrated information ΦMax specifies its quantity. Key results include the condensation of systems into major and minor complexes, the indirect relation of concepts to the external environment, the influence of anatomical connectivity on complexes, and the possibility of true "zombies" - unconscious feed-forward systems functionally equivalent to conscious complexes.