Moral judgement appears to presuppose free will, and science appears to presuppose determinism. Since the sciences are, for the most part, an established body of knowledge accepted by all, ethics must meet the challenge that it seems to contradict an axiom of science. In the apparent conflict between ethics and science, however, the onus lies on the moral philosopher, at least as much as on the philosopher of science, to examine the presuppositions on each side which seem to clash with each other. Science, it is generally thought, presupposes determinism and morality presupposes free will. If these presuppositions conflict, one have a fundamental inconsistency between two departments of thought—and not of thought alone, but of thought on which we base action. It has been thought that libertarianism means that acts, or some acts, are uncaused, and that the view denies the universality of the causal axiom, ‘Every change has a cause’.