Written by one of the world’s great experts in neurology, this brilliant work shows Yves Agid to be not only an accomplished neuroscientist but also an elegant essayist. Agid brilliantly summarizes, in sparkling prose, how our conscious and subconscious worlds intersect, and how conscious behaviors can be revealed by understanding the subconscious forces at work. In the great tradition of medical science, he uses examples from his clinical experience, in patients with Parkinson disease and other ailments, to illuminate how circuits within the basal ganglia of our brain regulate and influence many aspects of “voluntary” decision making. I cannot imagine a more approachable or enjoyable introduction to modern neuroscience than this beautiful little volume. Wise, charming, and playful, it should be essential reading for anyone who cares about how we think and behave.