Half a century of political Marxism and Soviet social science deflected Marxist thought from its canonical sources. Communism and Marxism were so intertwined by events of the twentieth century that it is difficult to see what remains of the latter after the demise of the former. Specifically, three foundational principles—“being determines consciousness,” the Asiatic Mode of Production, and “the ideas of the ruling class are the ruling ideas”—have been corrupted by heartfelt ideological commitments. A review of those principles against the background of Marxist writing on the history of science stakes out research frontiers that remain to be reconnoitered.