How should we imagine the situation in the case of Caligula? Do we suppose that there is a Roman emperor who behaves irrationally, whose speech is incomprehensible, whose perceptions of reality are disturbed, and who commits all sorts of crimes in this condition, without anyone’s intervening to stop him? If that had been so then an accusation of insanity would have had to be leveled, not at the emperor, but rather at the society that surrounded him: at the Roman aristocracy first and foremost, meaning the Senate that carried out his decisions, the magistrates in Rome who followed his instructions, and the military commanders and governors in the Empire who obeyed his orders. Blame would fall also upon the treasury officials who reallocated enormous sums at his behest, upon the people who saw him daily and advised him, and lastly upon the people of Rome themselves, who cheered him at the Circus and theater. If Caligula was mad, why wasn’t he silently removed from public view and placed under the care of a physician — just as was done when rulers in later European history became mentally ill?

By no means do all modern authors assume Caligula was insane. In view of the clearly denunciatory tendency of the ancient sources, a number of scholars — notably Willrich, Gelzer, Balsdon, and Barrett — have attempted to clarify what actually occurred under his rule. Great progress has been made on some particular questions: By comparing contemporaneous sources and earlier traditions with later ones, it has been possible to weed out false information, like the allegation of incest. Assertions by ancient authors that contradict the intention of their own works — statements that have crept in by mistake, as it were, or references to events too well known to be omitted — have been shown to be reliable. And finally scholars can draw on the entire body of surviving documents to become familiar with the broader context of the times and develop a theory of the politics, society, religion, and mindsets of the period; this makes it possible to distinguish between plausible and implausible reports in the sources.