The ‘theory of the humours’, says this author, ‘remained an inexact but powerful tool for centuries, surviving scientific changes and offering clarity to physicians’. Whether that clarity ever led to real understanding, though, is a question to which there is still no simple answer. Dr Arikha, an historian with polymathic interests, is described here as intertwining ‘the histories of medicine, science, psychology, and philosophy’ – which seems a good way of starting this exploration.

The story is important to psychiatrists because, as Arikha well describes, for well over 2000 years, humoural theory was used to portray most aspects of a person's character, psychology, medical history, tastes, appearance, and behaviour. Though Harvey's discovery of the circulation of the blood is said to have started undermining the theoretical credibility of the humours in the 17th century, some medical manuals were still recommending treatments on this basis in the early 1900s. If one extends the concept, it is suggested here, today's hormones, neurotransmitters and other particles can be seen as multiplications of the humours, though losing the overall simplicity of the four originals.

Successive sections of the book deal with antiquity (from Hippocrates and Galen), the Eastern middle ages, the Western (with apothecaries and alchemists), the Renaissance, the first scientific revolution, early modernity (including the birth of psychiatry) and from the early 20th century to today. There are 30 illustrations, not all of high quality, as well as primary and secondary references for each chapter and a reasonable number of explanatory endnotes. Psychiatrists will no doubt find more interest in the later chapters, though a longer historical view seems enough to encourage medical humility: ‘it was not much more comfortable to fall ill [in the later 18th century] than it had been in the fifteenth’.

Hippocrates had been the first to set out a ‘regimen for health’, based on the principle of humoural balance, whose advice on diet, purging, bathing, bleeding, alcohol and sexual relations was to remain influential for immense periods ahead. It can still be seen in the programmes of expensive health resorts.

It is admitted that a history of the humours ‘is not a history of the modern neurosciences’, but the author claims that recent psychiatry was borne on the back of concepts strongly influenced by humoural theory, notably the melancholic and phlegmatic temperaments, which reappeared in Eysenck's dimensions of personality. Arikha sees neurotic depression as the ‘closest modern incarnation of the natural sort of melancholy described by Burton’ in his classic work. She identifies a ‘constancy in the structure of intuitive explanation’, whereby the way people represent health and illness to themselves still shows evidence of humoural thinking.

Not every reader, though, will be fully convinced that there has been as much consistency as this view of medical history promotes. There are also some simplistic judgements which some would wish to qualify. The book's most useful place is as a companion to more systematic treatments of the history of psychiatry.