Postulate

(αἴτημα, postulatum, that which is asked or assumed to prove something else). "According to some, the difference between axioms and postulates is analogous to that between theorems and problems: the former expressing truths which are self-evident, and from which other propositions may be deduced; the latter, operations which may easily be performed, and by the help of which more difficult constructions may be effected." There is a difference between a postulate and a hypothesis. When you lay down something which may be, although you have not proved it, and which is admitted by the learner or the disputant, you make a hypothesis. The postulate, not being assented to, may be contested during the discussion, and is only established by its conformity with all other ideas on the subject.