Sacks opens the book by informing the reader that due to surgery on his right shoulder a month earlier, he needs to write with his non-dominant left hand. His body has adapted to this in a number of ways, including using his toes to grip objects when necessary. Some of these adaptations were intentional, while others he learned as he healed.

This is, Sacks proclaims, the ultimate paradox of disease and disorder: that while they may limit the human body in one way, “[O]ne may sometimes see them as creative too—for if they destroy particular paths, particular ways of doing things, they may force the nervous system into making other paths and ways” (xiv). Citing the work of neurologist A.R. Luria, Sacks posits that disorder and disease ought to challenge physicians to consider the brain not as a static or concrete organ, but one capable of ongoing evolution and adaptation. This is all the more extraordinary given the many small, vital parts of the brain that must work together in harmony.

The brain’s “remarkable plasticity” has changed the way Sacks views his own patients (xv). Whereas his earlier books tackled the subject of the preservation or loss of the self through disease and disorder, he has since realized that this is overly simplistic.