   Brandon, for example, has argued that the theory of natural selection should not be viewed as a body of general laws, but as the prescription for a research program. As such its central claims need not meet standards of testability, and fitness need not be defined in terms that assure the nontriviality, testability, and direct explanatory power of the theory of natural selection. In that sense, Brandon makes common cause with the later Popper. Popper originally argued the claim that the theory of natural selection was unfalsifiable pseudoscience. Later he came to hold that theory of natural selection was a scientifically respectable but nevertheless untestable organizing principle for biological science (Brandon 1990, 139–140).