Analogy — A logical, semantic, and argumentative procedure that establishes a proportional similarity between distinct domains, allowing the same term to be applied to different things without having exactly the same sense, yet without senses that are wholly unrelated. The word derives from the Greek analogía, which originally meant mathematical “proportion,” and it acquires philosophical weight in Aristotle, who distinguishes the ways a word can be said of several things: univocally (identical sense), equivocally (unrelated senses), and in relation to a central term, as in his famous analysis of “healthy,” which is said of the organism, of food, and of complexion by reference to health — the so-called pros hen or analogy of attribution. The medieval tradition, above all Thomas Aquinas, develops the analogia entis (analogy of being) to argue that predicates such as “good,” “wise,” or “being” can be applied to creatures and to God analogically: neither univocally, which would reduce God to the scale of the created, nor purely equivocally, which would leave us unable to say anything meaningful about him. Analogy thus becomes the middle path that makes discourse about the transcendent possible. In epistemology and science, analogical reasoning grounds hypotheses, models, and explanatory metaphors, as when the atom is compared to a planetary system: the inference transfers properties from a known case to a similar one, with merely probable rather than demonstrative force. Analogy is therefore distinct both from univocity — explored later by Duns Scotus — and from purely rhetorical metaphor, standing between identity and mere homonymy.
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