There can be few historical figures who have made such a powerful impact on the popular imagination as the Roman emperor Caligula (died AD 41). Yet an accurate reconstruction of his life and reign largely eludes us. This is paradoxical. The source material is plentiful, even lavish, by the standards of antiquity. The problem lies not so much in the quantity of evidence available, but in its quality. For our information we are obliged to draw on ancient...