The abrupt reversal of culturally ascribed primacy in the science–technology relationship—namely, from the primacy of science relative to technology prior to circa 1980, to the primacy of technology relative to science since about that date—is proposed as a demarcator of postmodernity from modernity: modernity is when ‘science’ could, and often did, denote technology too; postmodernity is when science is subsumed under technology. In support of that demarcation criterion, I evidence the breadth and strength of modernity’s presupposition of the primacy of science to and for technology by showing its preposterous hold upon social theorists—Marx, Veblen, Dewey—whose principles logically required the reverse, viz. the primacy of practice; upon 19th and 20th century engineers and industrialists, social actors whose practical interests likewise required the reverse; and upon the principal theorizers in the 1970s of the role of science in late 20th century technology and society. The reversal in primacy between science and technology ca 1980 came too unexpectedly, too quickly, and, above all, too unreflectively to have resulted from the weight of evidence or the force of logic. Rather, it was a concomitant of the onset of postmodernity. Oddly, historians of technology have remained almost wholly unacknowledging of postmodernity’s epochal elevation of the cultural standing of the subject of their studies, and, specifically, have ignored technology’s elevation relative to science. This I attribute to the ideological character of that discipline, and, specifically, to its strategy of ignoration of science.