… is from page 261 of Frank Knight ‘s 1956 collection On the History and Method of Economics ; specifically, it’s from Knight’s 1950 Presidential address to the American Economic Association, entitled “The Role of Principles in Economics and Politics “:
Since a fetish of “scientific method” in the study of society is one of the two most pernicious forms of romantic folly that are current among the educated, this theme ought to be developed at a length which is impossible here…. “Science,” in the meaning of the natural sciences, can of course do something toward both explaining and directing social events; and nothing is further from my purpose here than any belittling of the importance of ethics. What I insist upon is an understanding of the meaning and limitations of simple or statable principles in both areas. In the naive form in which both doctrines, scientism and moralism, are usually preached, both are antithetical to the principle or ideal of freedom; they imply, and if taken seriously would lead to, absolute authoritarianism.