When I use a word . . . Medical analogies and analogues

Some of the earliest uses of the words “analogy” and “analogue” related to medical matters, the former in Philip Barrough’s textbook, <i>The Methode of Physicke</i> (1583) and the latter in William Whewell’s <i>History of the Inductive Sciences</i> (1837), reporting the Theory of Analogues that the French naturalist Étienne Geoffroy Saint-Hilaire had propounded in his <i>Philosophie Anatomique</i> of 1818. Today, analogies of different kinds are often used in medical practice. Examples include: visual analogue scales; reasoning from known pharmacological properties of existing compounds to hypothesised ones in new compounds during drug development; and analogical models, such as structural pharmacokinetic models, especially those that are physiologically based, and the Markov models that are used in cost-effectiveness analyses of therapeutic interventions, typically medicines. But no matter how good or bad an analogy or an analogical model is, it can only establish the probability of a conclusion.