Full Idea
An axiom is a principle which must be grasped if anyone is going to learn anything whatever.
Clarification
'Axioms' are the initial assumptions
Gist of Idea
An axiom is a principle which must be understood if one is to learn anything
Source
Aristotle (Posterior Analytics [c.327 BCE], 72a17)
Book Reference
Aristotle: 'Posterior Analytics (2nd ed)', ed/tr. Barnes,Jonathan [OUP 1993], p.2