What first drew me to neurology was diagrams: long tracts in the cord, decussation in the pons, cortical maps. Neurology, somewhat like haematology, immunology and chemical pathology, can be a very diagrammatic specialty. My question is this: where in our diagrams do we place a person’s motivations, thoughts or feelings? Death certificates pronounce D to be due to C, which is due to B and so on, but this kind of logic is unconvincing when we try to incorporate psychological or social factors in a causal chain leading to a neurological symptom.

Many diseases are supposed to be caused by stressful events or, more vaguely, by “anxiety”. Anxiety hovers in neurological parlance some distance both from its DSM IV usage and from our everyday experience. Patients may protest (if they dare) that they have nothing to worry about, but neurologists will still often insist that their headaches, dizziness and so on are caused by anxiety. “Psychogenesis”, as Aubrey Lewis wrote, is a “confused …