Because every observation they ever make seems to corroborate the Darwinian tautology, most scientists probably do believe that the theory is universally true. But as the philosopher of science Karl Popper saw, the same was true of Freudianism. For good Freudians, everything seems to confirm the theory because it is protected against falsification by its own logic. Likewise Darwinism. "To say that a species now living is adapted to its environment is, in fact, almost tautological," Popper wrote. "There is hardly any possibility of testing a theory as feeble as this."