  A new axiom is proposed, the Ground Axiom, asserting that the universe is not
a nontrivial set forcing extension of any inner model. The Ground Axiom is
first-order expressible, and any model of ZFC has a class forcing extension
which satisfies it. The Ground Axiom is independent of many well-known
set-theoretic assertions including the Generalized Continuum Hypothesis, the
assertion V=HOD that every set is ordinal definable, and the existence of
measurable and supercompact cardinals. The related Bedrock Axiom, asserting
that the universe is a set forcing extension of a model satisfying the Ground
Axiom, is also first-order expressible, and its negation is consistent.
