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, The Methode of Physicke (1583) and the latter in William Whewell’s History of the Inductive Sciences (1837), reporting the Theory of Analogues that the French naturalist Étienne Geoffroy Saint-Hilaire had propounded in his Philosophie Anatomique 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.