SELF-EVIDENT

understood by itself, completely clear

See also primitive notion and axiom. In epistemology (theory of knowledge), a self-evident proposition is one that is known to be true by understanding its meaning without proof.Some epistemologists deny that any proposition can be self-evident. For most others, the belief that oneself is conscious is offered as an example of self-evidence. However, one's belief that someone else is conscious is not epistemically self-evident.The following metaphysical propositions are often said to be self-evident:A finite whole is greater than any of its parts.It is impossible for the something to be and not be at the same time in the same manner.
See more at Wikipedia.org...

Adjective
1. evident without proof or argument; "an axiomatic truth"; "we hold these truths to be self-evident"
(synonym) axiomatic, taken for granted(p)
(similar) obvious

(a.)
Evident without proof or reasoning; producing certainty or conviction upon a bare presentation to the mind; as, a self-evident proposition or truth.
  

Synonyms and related words:
absolute, actual, admitting no question, apparent, axiomatic, clear, clear as crystal, clear-cut, confirmable, crystal-clear, definite, demonstrable, demonstratable, discernible, distinct, evident, explicit, express, factual, historical, inappealable, incontestable, incontrovertible, indisputable, indubitable, inescapable, irrefragable, irrefutable, manifest, noticeable, observable, obvious, open-and-shut, palpable, patent, perceivable, perceptible, perspicuous, plain, plain as day, provable, proverbial, real, seeable, self-explaining, self-explanatory, tangible, testable, to be seen, TRUE, unanswerable, unconfutable, undeniable, unimpeachable, unmistakable, unquestionable, unrefutable, verifiable, visible