This is a landmark in science writing. It resurrects from the vaults of neglect the polymath Jerome Cardano, a Milanese of the sixteenth century. Who is he? A gambler and self-harmer, inventor and chancer, plagued by demons and anxieties, astrologer to the kings, emperors and popes, stubborn and unwordly, the son of a mathematician and a brothel keeper, but also unacknowledged discoverer of so much: probability theory, imaginary numbers, statistics, atomic physics and even quantum theory.