Abstract

This is the 1992 Marquette Aquinas lecture, the fifty-third in a distinguished series sponsored by the Wisconsin Alpha Chapter of Phi Sigma Tau. Though presented as a lecture, it is clearly the outline of a project that draws upon Ernan McMullin's considerable knowledge of the history of the philosophy of science and his realistic assessment of contemporary scientific inquiry. His is a large canvas and he admittedly paints with wide brush strokes. His major thesis, contra the positivism that lingers in some quarters, is that nothing other than a realist philosophy of science will enable one to make sense of contemporary natural science. A very literal reading of Aristotle leads him to distance himself from the Stagirite in certain respects, but McMullin's is fundamentally an Aristotelian analysis of science. To have science is not merely to know what is given in experience and codified in laws of nature, but to have an explanation of the given in terms of its proper causes. It is not enough to know that copper is malleable, conducts electricity, takes on a certain hue under such and such circumstances, and has a melting point of 1083 degrees centigrade. To have scientific knowledge of a material which has been used since antiquity is to know why it has these properties. Such knowledge is not obtained by simple observation, but is gained by the inference which leads to the postulation of an unobserved structure. McMullin believes that empiricists in the tradition of Bacon, Hume, and Mill are hard pressed to explain the inferential leap from observed effect to inferred cause. In passing he notes, "Though Bacon is trying very hard to separate himself from the Aristotelian tradition, one can still catch echoes of [Aristotle's] epagoge". Reviewing Mill's logic of science, McMullin observes that at the same time Mill was writing that causal relations hold only between observables, "the growing reliance of natural scientists on non-inductive inference to and from observables was leading to dramatic advances in fields like optics, chemistry and theory of gases".