Auxiliary statement or hypothesis

Any claim conjoined with a theory that is under test, in order to derive observable predictions from the theory. (Auxiliary statements are sometimes called "auxiliary hypotheses"; this name is somewhat misleading, since in a good test, the auxiliary statements are typically already well confirmed.)

The background knowledge required to draw testable consequences from a theory is found in the auxiliary hypotheses. No theory alone entails testable predictions, so auxiliary hypotheses always participate in the testing of a theory.