The three cardinal aims of science are prediction, control, and explanation, but the greatest of these is explanation. It is also the most inscrutable: Prediction aims at truth, and control at happiness, and insofar as one has some independent grasp of these notions, one can evaluate science's strategies of prediction and control from the outside. Explanation, by contrast, aims at scientific understanding, a good intrinsic to science, and therefore something that it seems one can only look to science itself to explicate.

Philosophers have wondered whether science might be better off abandoning the pursuit of explanation. Pierre Duhem (1954), among others, argued that explanatory knowledge would have to be a kind of knowledge so exalted as to be forever beyond the reach of ordinary scientific inquiry: it would have to be knowledge of the essential natures of things, something that neo-Kantians, empiricists, and level-headed practitioners of science could all...