Philosophers of science have generally lost patience with attempts to discredit theories as “unscientific” by using philosophical or methodological litmus tests. Such so-called “demarcation criteria” — criteria that purport to distinguish true science from pseudo-science, metaphysics and religion — have inevitably fallen prey to death by a thousand counter examples. Well-established scientific theories often lack some of the allegedly necessary features of true science (e.g., falsifiability, observability, repeatability, use of law-like explanation, etc.), while many disreputable or “crank” ideas have often manifested some of these same features. … As the philosopher of science Larry Laudan has shown, such contradictions have plagued the demarcation enterprise from its inception. As a result, most contemporary philosophers of science regard the question ‘what distinguishes science from non-science’ as both intractable and uninteresting. Instead, philosophers of science have increasingly realized that the real issue is not whether a theory is scientific, but whether a theory is true, or warranted by the evidence.