One of Oliver Sacks's subjects described being autistic among people as feeling like an anthropologist on Mars. Sacks took the image for his title and his attempt to understand a mind not by what it lacks, but by what it sees.

The title comes from Temple Grandin. Asked what it feels like to be autistic, she described the experience as being an anthropologist on Mars — observing human social behaviour from the outside, with curiosity and careful study, as a foreign culture one must learn rather than a native language one simply speaks. Sacks borrowed the image for his book because it described, with unusual precision, what he was trying to do in reverse: to enter the experience of minds very different from his own and understand them from within, on their own terms, rather than solely from the clinical vantage of what they deviate from.

The seven case studies in the book — a painter who loses all colour vision after an accident, a surgeon with Tourette's syndrome, a man blind since childhood who has his sight restored in middle age and finds the experience disorienting rather than liberating — are united by this methodological commitment. Sacks is not primarily interested in what is wrong with his subjects. He is interested in what their experience is like, and what it reveals about the mind's extraordinary capacity to build coherent worlds from radically different materials.

This places Sacks in a specific and unusual position in medical writing. The clinical tradition he was trained in treats deviation from neurological norms as deficit — as loss, damage, malfunction to be diagnosed and if possible corrected. Sacks never abandoned clinical rigour, but he kept asking a question that the clinical framework tends to foreclose: what is it like? Not what is wrong, but what is the texture of experience, what does the world look like and feel like and mean, from inside this particular way of being? That question requires a quality of imaginative attention that medicine does not formally teach, and that Sacks practised with unusual seriousness throughout his career.

He was not uncriticised for it. Some colleagues found his literary approach to case studies — the novelistic detail, the immersion in his subjects' inner lives — uncomfortably close to turning patients into characters. The tension is real. There is always a risk, in this kind of writing, that the writer's need for a compelling narrative shapes what gets seen and what gets left out, that the subject's experience is subtly organised around the observer's understanding of it. Sacks was aware of this, and the best passages in An Anthropologist on Mars carry a visible anxiety about it — moments where he registers the limits of his access, where the strangeness of another person's experience resists his attempts to enter it. Empathy in Sacks's work is not a technique that dissolves difference. It is a practice of sustained attention to difference — one that aims not to reduce another person's experience to something familiar, but to hold it in its full strangeness while remaining genuinely curious about what it contains.

Ric Burns's documentary Oliver Sacks: His Own Life (2020) is in some ways more moving than the books. It follows Sacks in the final months of his life, after his terminal cancer diagnosis, and finds him applying to his own experience the same quality of attention he brought to his subjects. He is curious about dying. He is curious about what it is like to know the end is close. He has no framework for it that feels adequate, and he says so. It is the most Sacksian thing imaginable.