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Karl Popper argued in 1974 that evolutionary theory contains no testable laws and is therefore a metaphysical research program. Four years later, he said that he had changed his mind. Here we seek to understand Popper's initial position and his subsequent retraction. We argue, contrary to Popper's own assessment, that he did not change his mind at all about the substance of his original claim. We also explore how Popper's views have ramifications for contemporary discussion of the nature of laws and the structure of evolutionary theory.