Caligula, the third emperor of Rome, figures today as the classic template for a Mad King. To a man, antique historians—Seneca, Tacitus, Suetonius, Cassius Dio, the whole bunch—reported that he was “mentally ill,” “sick,” and “insane.” Their list of his abominations is long and includes bloodthirstiness; incest; delusions of godhood; transvestism (a consequence of his appearances at state functions as Diana); the use of the legions to make war on Olympus (specifically, Neptune); the forcible prostitution of highborn Roman matrons; and the appointment of a favorite racehorse, Incitatus, to the Senate.

In the introduction to his new biography, Caligula, the Swiss classicist Aloys Winterling ranges himself in the camp of contemporary historians—by no means a tiny minority—who claim that the third emperor was not, in fact, mad. The argument is based both on the unreliability of the ancient sources, which are in critical disagreement about the catalogue of Caligula’s infamies, and on the fact that even his most outlandish behaviors do not fit with Roman ideas about insanity (which also absolved the afflicted of responsibility). Winterling quickly summarizes the proofs of this position and moves on to a far more interesting question: If the accounts of Caligula are indeed calumnies or misrepresentations, what exactly was it about his leadership that incited his contemporaries to vilify him so? The answer Caligula advances is that, in an attempt to redefine the relationship between ruler and Senate, the young princepsdeeply humiliated the Empire’s ruling class. His legacy was their