AXIOM

a universally recognized principle

a saying that is widely accepted on it's own merits

SYN - maxim

"He had always thought that the princple of love your neighbor as your self was an axiom which cultures from all around the world agreed upon."

"What bothered him about this leftist proffessor was not so much that he had views that went against his own but that he presented many things as axiom which Bill thought were rather controversial."

"He knew he had won the argument when he had buttressed his view with this axiom."