“One does not see with the eyes; one sees with the brain, which has dozens of different systems for analyzing the input from the eyes.”

I saw this on the shelf at the library and immediately picked it up – Oliver Sacks! This is my second book of his that I have read, following his best-selling The Man Who Mistook His Wife for a Hat and Other Clinical Tales. Hallucinations aren’t really something I had given a lot of thought to prior to this book. Like most, I categorized them in the realm of drugs or mental illness, something to be remedied. Sacks explores a lot of different types of hallucinations in this book, thought notably, not the kinds you see from schizophrenia or similar mental illness. As he mentions in the blurb, one can experience hallucinations for a variety of reasons. Though I have never had any myself, this book made me surprised at how common this sort of thing seems to be.One of the best parts of the book is when Sacks describes his own drug-fueled early adulthood as a medical resident, where he spent entire weekends doing some psychedelic or other, or self-medicating with questionable drugs. This, given his childhood history of migraines, certainly had me… side-eyeing him, but his descriptions are fascinating and honest. The other chapters go through different types of hallucinations, such as night-mares or phantom limbs. The mentions of case history from the 19th century and earlier were also interesting to read. There were some also thoughtful considerations about the nature of spiritual or enlightened experiences, and how hallucinations may have been responsible for a lot of historical ‘religious experiences’ or ‘visits from God’, etc. (Sacks tries not to press on this too much, but as an nonreligious person, I thought the analysis was spot-on.) At times, the book did seem to get repetitive and a bit too anecdotal; it would have been helpful to read this alongside some more modern scholarship about neuroscience. I read this book during a really stressful period in which I started studying for an exam that I must take, finishing two term-papers that were due last minute, and figuring out logistics for a move. Needless to say, this book took me longer to read than I anticipated, and I probably had a less enjoyable experience because of how fragmented my reading of this was. Thus, I’m going to be a little more lenient with this book.Most of all, this book helped reinforce the idea that perception is largely a gamble put on by your brain. Your brain receives inputs from your touch receptors, optic nerves, and olfactory nerves, and countless others. If any one of these many parts get jumbled up, your brain ‘perceives’ something else entirely. Sacks’s admiration of the brain and its wonderful capabilities is a subtle but underlying theme as with his other books, I imagine. Given that I have aphantasia, I wonder if I’m ever going to experience hallucinations like what is described in this book. The idea that perceiving something that isn’t there can bring someone so much joy and peace… or alternatively, so much pain and horror, is yet another thing about the brain that inspires awe and respect.