… is from page 109 of Leland Yeager’s and David Tuerck’s brilliant 1966 volume, Trade Policy and the Price System :
A distinction between empirical science and metaphysical speculation is justified. But we should not overdo the current fashion of carrying the supposed methods of natural science uncritically over into the social sciences. Natural scientists and economists alike are looking for facts of more general validity than those tied to specific historical circumstances. As the chemist Michael Polanyi once said, a determination of the speed at which water is running in a particular gutter, no matter how painstaking and precise, is not science. By and large, natural scientists have to arrive at their broad, generally valid, non-history-bound propositions by inference from painstakingly precise experimental measurements of many kinds. In economics, it so happens, the general, universally valid propositions can be derived from more direct observations, including introspection. It is illegitimate to identify hard-won facts with solid empiricism and easily-arrived-at facts with useless metaphysical speculation…. Obscure and uncertain facts that quite well may not hold true in times and places other than those for which they were determined seem like a shaky basis for propositions of generality and depth.