The Master and His Emissary, By Iain McGilchrist

Iain McGilchrist's ambitious and provocative study, subtitled "The Divided Brain and the Making of the Western World", should send thinkers and cultural commentators into the stratosphere. In it, he not only seeks to marry neurological science with a history of Western art and culture, but also to argue that that link between the two is a negative one. It is not until the penultimate chapter, though, that he nails his colours to the mast and declares himself a Romantic, who deplores the Enlightenment's privileging of reason and rationality.

Why he deplores those values can only be horribly simplified in a short review, but here goes: Romanticism is "a manifestation of right-hemisphere dominance" in the brain; rationality is represented by the left hemisphere. Both hemispheres have aspects of each other, of course, but the lack of exact symmetry between the two has suggested a warring between them. McGilchrist argues effectively that we made a conscious choice, over time, to privilege one side of the brain over the other, and that we made the wrong decision. When the right hemisphere is incapacitated, he says, the left part of the body "ceases to exist"; whereas for the left hemisphere, the body is already "something from which we are relatively detached". That left-hemisphere detachment has prevailed in art and science since the Ancients, McGilchrist argues, presumably because it avoids the messiness of emotion, how we treat the body, and so on.

We live, he argues, "in two different types of world". It is a powerful argument to suggest that humans have been suppressing parts of the brain in the interests of the state, or organised religion, say; and it is also a fascinating one that has real implications for cultural shifts. This may well be a book that comes into its own in the years to come.