What was wrong with Nietzsche? Why did he go mad? The question has been much discussed, partly by members of the medical profession who have taken to diagnosing the great dead as a recreation, and partly by Nietzsche scholars. The latter usually have a vested interest in the outcome. Broadly, if they are admirers of Nietzsche, they favour a purely physiological diagnosis – usually the traditional one of syphilis – while if they are opponents they favour a psychological one. If, that is, Nietzsche's madness was the product of psychological factors arising from within his personality, it becomes possible to make the argument that his philosophy is tainted by those same factors; that it is, as the reviewer of Beyond Good and Evil claimed (p. 406 above), ‘pathological’. Opponents generally wish to open up this possibility, admirers to close it down.

Nietzsche suffered, we have seen, time after time, awful bouts of depression that sometimes brought him close to suicide (p. 357 above). In June 1887 he describes himself as having been depressed for an entire year, a condition (Winston Churchill's ‘black dog’) which he describes as a worse form of suffering than all his physical ailments, ‘the worst penalty there is for life on earth’. Yet at other times he experienced moments of great elation, elation coloured by touches of grandeur, and increasingly by megalomania.