History, Scientific Methodology, and the "Squishy" Sciences

One item of consensus that has emerged from research in history and philosophy of science over the past few decades is that there is not one scientific method but many. Although this has not yet found its way into many introductory science textbooks, it is a result that resonates with most scientists who recognize that research communities use many heterogeneous methods to pursue their theoretical and empirical tasks. The diversity of scientific methodology is on display historically in the edited volume Science Rules: A Historical Introduction to Scientific Methods. Peter Achinstein skillfully juxtaposes key texts on scientific methodology from the past 400 years with contemporary commentary and discussion. The format is illuminating. Descartes's rationalism is illustrated by three different examples and then dissected by Daniel Garber; Newton's inductivism regarding gravitation is seen through different sections of the Principia, then carefully considered by I. B. Cohen and criticized by Whewell; hypothetico-deductivism is exemplified in the Mill-Whewell debate on the wave theory of light, along with famous excerpts from Karl Popper; the "antirealism" of Duhem and van Fraassen is set beside the "realism" of Perrin and Salmon; Galileo's refutation of the tower argument is the centerpiece for both Feyerabend and Kuhn to (very differently) reject universal scientific methodology. In addition to his helpful introductory overviews to each section, the inclusion of Achinstein's own scholarly articles that treat similar topics emphasizes how these issues have ongoing relevance in philosophy of science.

An advantage of Achinstein's editorial tactic is in demonstrating how particular philosophical issues about scientific methodology are recurrent. The Mill-Whewell debate highlights the role of induction. For Whewell, the wave theory of light is substantiated by its fulfilling three criteria of theoretical adequacy in addition to accounting for known light phenomena: (1) it accurately predicts new phenomena; (2) it explains and predicts phenomena of a different kind from which the theory was originally formulated; and (3) it exhibits coherence and simplicity as the theory develops over time. Mill objects that Whewell's methodological recommendations do not address the origin of theories that are then evaluated according to these criteria. Since different theories can yield similar predictions, an inductive process must be utilized to formulate them in the first place. Popper rejects both of these because they involve inductive inferences rather than deductive ones. Achinstein's more recent analysis points out how the arguments of wave theorists such as Fresnel or Young can be reconstructed in terms of probabilistic inductive inferences.

Although this book is well conceived, it is focused on the "hard" physical sciences and says little about either the putative "soft" sciences such as sociology or the middle ground of biology and medicine (the "squishy" sciences, as John Earman likes to call them). Achinstein is fully aware of this and flags it in his introductory remarks: "The scientific examples pertain exclusively to physics. There are three reasons for this: historically much philosophy of science has been derived from concerns about physics; most of the scientists who have advocated scientific methods or rules that are supposed to be applicable to all the sciences have been physicists; and this focus reflects the interests of the editor" (p. 4). Leaving aside the last rationale, which is difficult to quarrel with, the other two reasons can be challenged. It is not at all clear (if not demonstrably false) that historically most philosophy of science has been motivated by physics. Maybe this was true in the middle part of the 20th century, with respect to logical empiricists and some of their students. But even this is questionable: Carnap, Feigl, Hempel, and others exhibited persistent interest in the conceptual foundations of psychological research. Some of the earliest known reflections on scientific methodology found in Aristotle were driven as much by biology as by physics, and there is no shortage of methodological reflections on medical investigation in the Hippocratic writings or in the work of Galen. Aristotelian influence reaches down into the Renaissance and thereafter...