begged the question

Begged the question originally meant assumed the conclusion in an argument—using as a premise the very thing you're trying to prove.

Saying the Bible is true because it's the word of God begs the question of whether it is the word of God.

In common usage, the phrase has shifted to mean raised or invited the question: His absence begged the question of where he'd been all night.

Traditionalists object to this newer sense, but it now dominates everyday speech.