At first glance, Reilly's thesis appears reasoned and structured.1 But his argument is flawed, such that he misses the most important reason for the distinction between psychiatry and neurology, with which a Martian would surely concur. Reilly states that ‘most organs (such as lungs, kidneys, hearts and eyes) are treated by a single medical specialty’. Not so. A cardiac surgeon operates on the heart, determines which patients would benefit from surgery, and manages pre- and post-operative care. A cardiologist's talents lie elsewhere. Similarly, the division between psychiatry and neurology is defined by knowledge and skill. This is no artificial distinction imposed by a quirk of history, but reflects a difference in the very nature of the knowledge and skill base developed by doctors as they specialise. One cannot expect every trainee neurologist to additionally become expert in, say, holistic and developmental assessment, psychological formulation and complex diagnostic classifications of a nature unknown outside psychiatry. These are for trainee psychiatrists to focus on. Doctors do not practise in isolation, but as members of multidisciplinary teams. Nurses and others develop similarly specialist knowledge and skills to work with patients with broadly different presentations. Of course, there are small areas of overlap, but Reilly falsely dichotomises these to fuel his argument: I had no idea conversion disorder was the preserve of neurologists. At best, he puts forward a case for closer working and more shared care of patients between the two specialties. But two specialties they most assuredly are.