An orgy, the dictionary tells us, is "a wild gathering, marked by promiscuous sexual activity, excessive drinking, etc." Burgo Partridge tells us precisely what that has meant down through the ages. He begins with the Greeks, who celebrated sexuality at Dionysian festivals, and the Romans, who imported unwholesome brutalities into their orgiastic celebrations. We then learn of the penchant for group sex displayed by medieval popes, the junketings of Restoration England, the aristocratic hedonists of the Hellfire Club and Scotland's notorious Wig Club, the orgiastic tastes of Casanova and the Marquis de Sade, right into the 20th century and the bizarre excesses of Aleister Crowley.