first truth

plural first truths

1. A statement that is not proved but rather supposed or held as obvious, forming together with other such statements the basis of a system of statements obtained from them by inference; an axiom.

   1 more example

   These are the principles also treated of, in a former work, under the name of First Truths. They are not, like our knowledge of the other kind, the result of any process either of investigation or of reasoning; and, for the possession of them, no man either depends upon his observation, or has recourse to that of other men.

   1836, John Abercrombie, Jacob Abbott, The Philosophy of the Moral Feelings