  The two features of prescriptivity and universalizability remained the twin pillars of Hare’s theory ever afterwards. The term “universalisability” was to become the title of a slightly later paper (1954/5) which also sorted out a confusion that causes real trouble in Aristotle and Kant. “General” terms (such as “man” or “Greek”) contrast with “singular” ones (such as “Socrates”). However, in the case of maxims, one needs to keep two distinctions apart: a maxim may be “universal”, rather than “singular” or (ambiguously) “particular”, in referring to no individuals (unless within the scope of a preposition such as “like” which converts the name of an individual into the vague specification of a kind); a maxim may also be “general”, rather than “specific”, in identifying a wide class of agent or act—a difference that is one of degree (so that the universal rule “Always give true evidence” is more specific than “Always tell the truth”, and more general than “Always give true evidence on oath”). Any discussion of the practicality and acceptability of “general principles” needs to keep these distinctions apart. Hare’s clarity on the matter is his most important non-disputable contribution to philosophy.