'Nature' is a highly important term in the ethical discourse of the Middle Ages and, as such, a leading concept in medieval literature. This book examines the moral status of the natural in writings by Alan of Lille, Jean de Meun, John Gower, Geoffrey Chaucer, and others, showing how-particularly in the erotic sphere-the influences of nature are not always conceived as wholly benign. Though medieval thinkers often affirm an association of nature with reason, and therefore with the good, there is also an acknowledgement that the animal, the pre-rational, the instinctive within human beings may be validly considered natural. In fact, human beings may be thought to be urged almost ineluctably by the force of nature within them towards behaviour hostile to reason and the right.