With the relentless rise of neuroscience, it is becoming increasingly difficult to hold on to the complexity of subjective experience. If we can show that seeing unknown people by the bedside, or hearing voices in an empty room, is caused by damage to the brain, then, one could ask, is that not enough?
And is it not reassuring to be told, for example, that the bewildering encounters a person might have with benign or terrifying others (who are not “really” there) are due to some kind of cortical misfiring rather than to madness?
Maybe all such experiences are produced by bangs in the brain, whether as a result of accidents, illness, drug abuse or something genetically unlucky.
Perhaps that even extends to religious experiences: moments of awesome encounter with an Other who seems to transcend everything and to be wholly benign and loving. Maybe God is a kind of phantom limb, hallucinated to make sense of a neurological gap.
Oliver Sacks’s new book gives rise to a lot of thoughts of this kind. It is built out of case examples of people whose hallucinations vary, from those surrounding sleep, through auras preceding epilepsy and migraine, to deliriums and what he calls “phantoms, shadows and sensory ghosts”. He includes letters from readers of his other books, attesting to their own hallucinatory experiences and draws on a large back-catalogue of 19th- and 20th-century neurological writing to document the durability and pervasiveness of hallucinations.
He also offers a long, engaging look at his own indulgence in psychotropic drugs and the effects they had on him, and describes his life-history of powerful migraines that had an important influence on his choice of career.
These personal sections, which evoke the terror and curiosity that Sacks felt, the damage done and the gains made, are in many ways the strongest in an uneven and sometimes emotionally flat book. They are written from inside and outside at the same time, combining the intimacy of subjectivity with the clarity of academic thought, in a way that illuminates both sides of the bargain.
This inside-outside combination is the main achievement of Hallucinations. Ethically, one might say, it offers something very important. By concentrating on hallucinations outside the sphere of psychiatry, it shows just how common and usually explicable they are.
But it also attests to their phenomenological force. These experiences can be crippling or transformative; they can mean an enormous amount to the people who have them. Sacks supplies here a reminder that minds and brains go together, and that what happens in one domain is of deep, and often deeply moving, importance for what happens in the other.
