Don't you just love him? Heck look at this way, at least he makes us laugh!
Try this; in logic, an indemonstrable first principle, rule, or maxim, that has found general acceptance or is thought worthy of common acceptance whether by virtue of a claim to intrinsic merit or on the basis of an appeal to self-evidence. An example would be: “Nothing can both be and not be at the same time and in the same respect.”
http://www.britannica.com/eb/article-9011480/axiom
Oxygen exists is an axiom, to reject such an assumption you make a complete idiot of yourself, you got lungs, you breat air, mostly made up of oxygen therefore, oxygen exists. Gravity is an axiom, to refuse this postulate, you can make a complete ass of yourself "as you often do" LOL..
*Etymology: Latin axioma, from Greek axiOma, literally, something worthy, from axioun to think worthy, from axios worth, worthy; akin to Greek agein to weigh, drive -- more at AGENT
1 : a maxim widely accepted on its intrinsic merit
2 : a statement accepted as true as the basis for argument or inference : POSTULATE 1
3 : an established rule or principle or a self-evident truth
http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=axiom
**1. a self-evident truth that requires no proof.
2. a universally accepted principle or rule.
3. Logic, Math.a proposition that is assumed without proof for the sake of study the consequences that follow from it.
http://www.infoplease.com/dictionary/axiom
This enough authoraty for ya?