Marxism and Freudianism are Not Science

The difficulties connected with my criterion of demarcation (D) are important, but must not be exaggerated. It is vague, since it is a methodological rule, and since the demarcation between science and nonscience is vague. But it is more than sharp enough to make a distinction between many physical theories on the one hand, and metaphysical theories, such as ' psychoanalysis, or Marxism (in its present form), on the other. This is, of course, one of my main theses; and nobody who has not unde...