 Medieval theories of analogy were a response to problems in three areas: logic, theology, and metaphysics. Logicians were concerned with the use of words having more than one sense, whether completely different, or related in some way. Theologians were concerned with language about God. How can we speak about a transcendent, totally simple spiritual being without altering the sense of the words we use? Metaphysicians were concerned with talk about reality. How can we say that both substances (e.g., Socrates) and accidents (e.g., the beardedness of Socrates) exist when one is dependent on the other; how can we say that both God and creatures exist, when one is created by the other? Medieval thinkers reacted to these three problems by developing a theory which divided words into three sorts, independently of context. Some were univocal (always used with the same sense), some were purely equivocal (used with quite different senses), and some were analogical (used with related senses). Analogical terms were thought to be particularly useful in metaphysics and theology, but they were routinely discussed in commentaries on Aristotle’s logic and in logic textbooks. The background to the discussion was given by what is often called the analogy of being or metaphysical analogy, the doctrine that reality is divided both horizontally into the very different realities of substances and accidents and vertically into the very different realities of God and creatures, and that these realities are analogically related. Nonetheless, the phrase “medieval theories of analogy” as used here will refer to semantic analogy, a set of linguistic and logical doctrines supplemented, at least from the fourteenth century on, by doctrines about the nature of human concepts.