‘An axiom, postulate or assumption is a statement that is taken to be true, to serve as a premise or starting point for further reasoning and arguments. The word comes from the Greek axíōma (ἀξίωμα) “what is thought fitting”, “that which is thought worthy or fit” or “that which commends itself as evident”.’

From Axiom on Wikipedia

‘In an axiomatic system you start with premises that are known to be true, and rules that are known to be valid, in order to produce new statements that are guaranteed to be true. Conclusions can be reached by manipulating symbols according to sets of rules. Euclidean geometry is the classic example of the kind of generally useful tools made possible by formal axiomatic systems.’ P. 46, Tools for Thought by Howard Rheingold

See maxim.