The Integrated Information Theory (IIT) formulated for the first time in 2004 by the neuroscientist Giulio Tononi, is a theoretical framework aiming to scientifically explain phenomenal consciousness. The IIT is presented in the first part of this work. Broadly speaking, integrated information is an abstract quantitative measure of the causal power a system has on itself. The main claim of IIT is the identity between informational structures and experience. The nature of this identity will be the subject of the second (...) part. One can interpret the IIT as a fundamental law of nature connecting the physical domain to the mental domain. The philosophical implications of such a claim are numerous and they are subject to criticism. This will be the main concern of the third and last part. (shrink)