We can distinguish two kinds of moral universalization tests for practical principles. One requires that the universal practice of the principle, i.e., universal conformity to it by all agents in a given world, satisfies some condition. The other requires that conformity to the principle by any possible agent, in any situation and at any time, satisfies some condition. We can call these universal practice and universal applicability tests respectively. The logical distinction between these tests is rarely appreciated, and many philosophers (...) systematically confuse them with each other. In practice, UP tests are more frequently used to defend deontological norms, while UA tests are used to defend consequentialist norms. Both conceptual argument and practical examples of their applications will show that UA tests are decisively superior to UP tests for grounding moral norms, casting greater doubt upon deontological theories which rely upon the latter unless they can reformulate their arguments using some version of a UA test. (shrink)