Phi: A Voyage from the Brain to the Soul
Giulio Tononi
Pantheon Books, 2012 ($30)

In his book Phi, neuroscientist Tononi imagines Galileo Galilei, the 16th-century astronomer, drifting into a dream that takes him on a journey to understand consciousness. Part fantasy novel, part scientific expedition, Phi follows Galileo as he puzzles over what consciousness is, where it comes from and what beings can possess it.

Tononi invokes Dante's Divine Comedy by having guides, all groundbreaking scientists, introduce Galileo to different facets of consciousness. The first guide is the sharp-tongued biologist Francis Crick, who reveals the parts of the brain that contribute to consciousness. The two men visit mathematician and astronomer Nicolaus Copernicus, who has suffered a cerebral hemorrhage and fallen into a vegetative state. His misfortune illustrates how damage to the corticothalamic system can destroy consciousness. In a healthy individual, this system regulates functions such as sleep, awareness, memory and thought.

Alan Turing, the mathematician, becomes Galileo's second guide and challenges him to define consciousness. Turing suggests that even simple machines can produce a conscious experience. Galileo disagrees, arguing that although a digital camera has the capacity to store tremendous amounts of information, a brain can handle more. Communication among neurons allows the brain to generate knowledge; this integration of ideas is what creates consciousness. Galileo dubs this concept of consciousness “phi.”

Finally, Charles Darwin walks Galileo through the implications of phi—what expands consciousness, for example, and how phi can diminish with time. In the library of poet and essayist Jorge Luis Borges, they observe how imagination enhances the quality of our conscious experience. In a Kafkaesque incident, however, the dark side of phi emerges: manipulation of our neural circuitry is shown to elicit the most excruciating pain. Galileo also learns how consciousness can be nurtured or extinguished and how it evolved, having surfaced in other animals and in humans before birth.

Along the way, a mysterious notetaker reflects on each chapter, identifying the artistic, scientific and historical references that inform Galileo's journey. Although these notes allow the reader to identify Tononi's allusions, they also compound the confusion, adding one more voice to the cacophony. It is possible that his ambitious approach is intended as a metaphor: as with the dialogue among neurons, the conversation among ideas in the book shapes our conscious experience. The reliance on metaphor, however, gives Tononi's explanations an oblique, hazy quality. Phi, like Galileo's wending path, remains unwieldy and mysterious.