"Natural Law," International Encyclopedia of the Social Sciences, Vol. 2 (1968). Reprinted in Studies in Platonic Political Philosophy.
Natural law, which was for many centuries the basis of the predominant Western political thought, is rejected in our time by almost all students of society who are not Roman Catholics. It is rejected chiefly on two different grounds. Each of these grounds corresponds to one of the two schools of thought which are predominant today in the west, i.e. positivism and historicism. According to positivism, genuine knowledge is scientific knowledge and scientific knowledge can never validate value judgments; but all statements asserting natural law are value judgments. According to historicism, science (i.e. modern science) is but one historical, contingent form of man’s understanding of the world; all such forms depend on a specific Weltanschauung; in every Weltanschauung the “categories” of theoretical understanding and the basic “values” are inseparable from one another; hence the separation of factual judgments from value judgments is in principle untenable; since every notion of good and right belongs to a specific Weltanschauung, there cannot be a natural law binding man as man. Given the preponderance of positivism and historicism, natural law is today primarily not more than a historical subject.