The neuroscientist Giulio Tononi at the University of Wisconsin has worked on his "Integrated Information Theory" or simply "Phi" since 2004. Tononi's strategy is to first define the properties of consciousness and then infer the properties that a physical substrate needs to have to have in produce those other (phenomenological) properties. Tononi has designed an algorithm for calculating the degree of network interconnectedness. This quantity, known as Phi, measures the amount of information that is not localized in the individual parts of the system but is spread out over the entire network. Tononi's big postulate is that Phi measures the degree of consciousness because that is the physical property that accounts for the phenomenological properties of consciousness. The value of Phi is high in a hierarchical system composed of independent clusters that interact tightly, such as in the human brain. Tononi's algorithm (also implemented in software) generates a sequence of state transitions that corresponds to the system's stream of consciousness. Note that the system does not need to be a biological system.

This time Giulio Tononi has written a Dantesque "Divine Comedy" that takes the reader from Hell to Paradise via Purgatory following not Dante but Galileo (the father of modern science). In each of the three realms Galileo is led by a different person, just like Dante in his journey. The first part, led by a neuroscientist, is a tour of how the brain works. The second part, led by Alan Turing, explains how consciousness can arise from the integration of information (what Tononi called "phi"). The third part, led by Charles Darwin, speculates that consciousness might still be evolving, just like everything else that is alive. Along the way Galileo has encounters with Copernicus and Borges that help clarify issues here and there. The book has little to offer in terms of groundbreaking theories. Tononi's "phi" is hardly more than a personal belief. His work with neuroscientists such as Edelman has not proven much in that direction, other than the very vague fact that some kind of integration is obviously important for me to be able to think and operate. The book is nice to read, but, by the end, there is little one can write about. Cute idea, though.

See instead Edelman Gerald & Tononi Giulio: "A Universe of Consciousness" (Basic, 2000)

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