Aleister Crowley is the most notoriously transgressive figure in modern Western esotericism, and his best known precept is "Do what thou wilt". This article seeks to elucidate the place of Crowley's precept in the history of esotericism and transgression. More specifically, it seeks to make two points. First, it shows, through an investigation of its sources and influences, that the precept had highly transgressive overtones in the period when Crowley adopted and popularised it. These overtones extended to sexual excess, religious deviancy and fascist politics. Second, it argues that the precept was repurposed in a major way in the latter part of the twentieth century. The precept became domesticated, as the founders of the Wicca movement subsumed it into their own ethical maxim, the "Wiccan Rede". This development serves as an example of how some of the more transgressive and problematic elements of the Western esoteric tradition have come to be softened and obscured in contemporary mass-market, suburban forms of practice such as Wicca.