 One source for the theory of analogy is the doctrine of equivocal terms found in logic texts. Until the early twelfth century, the only parts of Aristotle’s logic to be available in Latin were the Categories and On Interpretation, supplemented by a few other works including the monographs and commentaries of Boethius. The Categories opens with a brief characterization of terms used equivocally, such as ‘animal’ used of real human beings and pictured human beings, and terms used univocally, such as ‘animal’ used of human beings and oxen. In the first case, the spoken term is the same but there are two distinct significates or intellectual conceptions; in the second case, both the spoken term and the significate are the same. We should note that equivocal terms include homonyms (two words with the same form but different senses, e.g., ‘pen’), polysemous words (one word with two or more senses), and, for medieval thinkers, proper names shared by different people. By the mid-twelfth century the rest of Aristotle’s logic had been recovered, including the Sophistical Refutations in which Aristotle discusses three types of equivocation and how these contribute to fallacies in logic. For writers throughout the later middle ages, the discussion of analogical terms was fitted into the framework of univocal and equivocal terms provided by Aristotle and his commentators. We will return to this below.