…[I]t ought to be said that there exists no method-oriented definition of science under which all parts and sections of physics, chemistry, biology, geology, and other generally recognized natural sciences could qualify as “sciences.” Definitions of science which stress the theoretical system, the network of logically interrelated hypotheses using mental constructions of ideal exactness, undoubtedly exclude large parts of chemistry and biology. Definitions stressing repeatable experiments and verified predictions clearly exclude the parts of biology, geology, and cosmology which deal with the evolution of life, of the earth and of the universe. And even within physics — the discipline which is the science par excellence because most definitions of science were formulated with physics in mind as the model — the authorities are by no means agreed as to whether the deductive system or the inductive technique constitutes its scientific nature.
— Fritz Machlup, “The Inferiority Complex of the Social Sciences,” in Mary Sennholz and Vernelia Crawford (eds.), On Freedom and Free Enterprise: Essays in the Honor of Ludwig von Mises (Princeton: D. Van Nostrand Company, 1956), p. 164.
Machlup’s essay, suggested to me recently, is a great introduction to the idea that a strict definition of the “scientific method” — the one most commentators seem to have in mind when they judge economic’s claim to being a science — would exclude much of what we do consider science. It also serves as a reminder that what may call for a different method in economics is not a result of differences between the natural and the social sciences, but a problem that stems from the study of complex phenomena (something that exists in the natural sciences, as well).