‘What is madness?’ is a corker of a question, and it is perhaps unfair to be somewhat disappointed with Darian Leader’s attempt to answer it. Don’t get me wrong: the book has its merits. It contains many excellent clinical observations. Given the arcane liturgy of the Church of Lacan, I was particularly pleased by the reference to a patient who, bamboozled by talk of the Lacanian concept of the Name of the Father, wanted to have it surgically implanted – a perfect example of the psychotic tendency to misplace the abstract as concrete (and vice versa). We meet a man who became so unsure of the meaning of words that he had to carry a dictionary on his back. Another found relationships difficult, because he would perceive the face of the girl he was interested in as a skull, and see his own skeleton through his skin during sex. Leader is good on the fact that a real event and a delusion are perfectly compatible – the spouses of some people with delusional jealousy are unfaithful – and on the complexities of causation: in some cases a belief is not mistaken, but the unshakable quality of certainty attached to it can be a sign of psychosis. He observes, as Kretschmer did, the either/or, black-and-white nature of the schizophrenic world. On another theme, one of Leader’s patients catalogued her symptoms, and in her sessions with him referred only to their numbers. These are beautiful insights into the nature of psychotic disorders, the sort of things that tend to get filtered out of the colourless, systematised descriptions that are too common in mainstream psychiatric literature.