Self-evident; intuitively true; evident beyond contradiction.

of a proposition; necessarily true or logically certain

An apodeictic proposition in Aristotlean logic asserts things which are necessarily or self-evidently the case or impossible, in contrast to assertoric propositions which merely assert that something is or (is not) the case, or problematic propositions which assert only the possibility of something being true. For instance, "Two plus two equals four" is apodeictic. "Chicago is larger than Omaha" is assertoric.