 Karl Popper is probably the most famous proponent of prediction in the history of philosophy. In his lecture “Science: Conjectures and Refutations” Popper recounts his boyhood attempt to grapple with the question “When should a theory be ranked as scientific?” (Popper 1963: 33–65). Popper had become convinced that certain popular theories of his day, including Marx’s theory of history and Freudian psychoanalysis, were pseudosciences. Popper deemed the problem of distinguishing scientific from pseudoscientific theories ‘the demarcation problem’. His solution to the demarcation problem, as is well known, was to identify the quality of falsifiability (or ‘testability’) as the mark of the scientific theory. 