What is that thing where I make a statement that contains its own truth value internally without the need to rely on anything outside itself or at least the need to refer to something externally?

axiom?

tautology?

first principle?

Tautology?

self-evident

Axiom.

If you're talking philosophy, analytic?

https://en.wikipedia.org/wiki/Analytic%E2%80%93synthetic_distinction

The analytic–synthetic distinction is a semantic distinction used primarily in philosophy to distinguish between propositions (in particular, statements that are affirmative subject–predicate judgments) that are of two types: analytic propositions and synthetic propositions. Analytic propositions are true or not true solely by virtue of their meaning, whereas synthetic propositions' truth, if any, derives from how their meaning relates to the world.[1]

The philosopher Immanuel Kant uses the terms "analytic" and "synthetic" to divide propositions into two types. Kant introduces the analytic–synthetic distinction in the Introduction to his Critique of Pure Reason (1781/1998, A6–7/B10–11). There, he restricts his attention to statements that are affirmative subject–predicate judgments and defines "analytic proposition" and "synthetic proposition" as follows:

• analytic proposition: a proposition whose predicate concept is contained in its subject concept

• synthetic proposition: a proposition whose predicate concept is not contained in its subject concept but related

per se notum

Intrinsic?