Of all the manifestations of wild and extravagant behaviour exhibited by Caligula during his brief reign, nothing has better served to confirm the popular notion of his insanity than his apparent demand to be recognised as a god. Cruelty and incompetence may be unattractive traits of a ruthless despot, but they do not in themselves prove mental instability. A claim to divinity, however, seems inseparable from madness. The evidence for the supposed cult of Caligula in Rome is characteristically confused and incomplete, and must be evaluated with perhaps even more than the usual caution and scepticism. Most importantly, however, we must be careful not to impose on the ancient world our own preconceptions of what constitutes a sound and healthy relationship between the human and the divine.