What Is the Integrated Information Theory of Consciousness?

In the first instance, IIT is formulated as a theory of the physical basis of the 'degree' or ‘level’ or ‘amount’ of consciousness in a system. In addition, integrated information theorists have tried to provide a systematic theory of how physical states determine the specific qualitative contents of episodes of consciousness: for instance, an experience as of a red and round thing rather than a green and square thing. I raise a series of questions about the central explanatory target, the 'degree' or ‘level’ or ‘amount’ of consciousness. I suggest it is not at all clear what scientists and philosophers are talking about when they talk about consciousness as gradable. I also raise some questions about the explanation of qualitative content.