Why is the brain divided? The difference between right and left hemispheres has been puzzled over for centuries. In this book, Iain McGilchrist draws on a vast body of recent brain research, illustrated with case histories, to reveal that the difference is profound - not just this or that function, but two whole, coherent, but incompatible ways of experiencing the world. The left hemisphere is detail oriented, prefers mechanisms to living things, and is inclined to self-interest, where the right hemisphere has greater breadth, flexibility, and generosity. This division helps explain the origins of music and language, and casts new light on the history of philosophy, as well as on some mental illnesses.