Axiom

From Logic

In traditional logic, an axiom or postulate is a proposition that is not proved or demonstrated or, in some cases even demonstratable in theory, but considered to be either self-evident, or at the least required for a system to work. Therefore, its truth is taken for granted, and serves as a starting point for deducing and inferring other (theory dependent) truths.

In some cases, an axiom is defended through retortion.