Round this point centres the whole dispute about the methods proper to political theory. There are, broadly speaking, two schools of political theorists, if we set aside the psychologists. One school, by collecting facts, aims at reaching broad generalisations about what actually happens in human societies; the other tries to penetrate to the universal principles at the root of all human combination. For the latter purpose facts may be useful, but in themselves they can prove nothing. The question is not one of fact, but one of right.