 On one familiar view, we can know a priori the fundamental moral principle (or principles), e.g., the principle that one ought to perform the action that has the overall best consequences, or the principle that one ought to act in accordance with virtue, or whatever the basic moral principle really is. Some hold we can know the principle via analysis or because it defines the moral term it is about. We can then know every day moral propositions about particular actions or types of actions by inferring them from the fundamental principle in conjunction with empirical facts.