"Power, Patronage, and the Authorship of Ars" is a study of books on the mechanical arts that appeared in the fifteenth century from Italy and south Germany. At this time a significant proliferation of such books occurred, some profusely illustrated, others exclusively textual. They include Latin books on military apparatus and other kinds of machines, German-language codices on gunpowder artillery and machines, humanist treatises on painting, sculpture, architecture, and the military arts, and vernacular writings on such subjects by practitioners. The author argues that the patronage that encouraged the creation of such books developed because of a new close alliance between political and military praxis and the mechanical arts. She suggests that such authorship elevated the status of the mechanical arts by explicating them in writing, rationalizing them, and associating them with ancient traditions. They were thus prepared for appropriation by the new experimental philosophy of the next era.