nApagoge(Logic) An indirect argument which proves a thing by showing the impossibility or absurdity of the contrary.
Century Dictionary and Cyclopedia
napagogeIn logic: Abduction (which see). The demonstration of a proposition by the refutation of its opposite (from Aristotle's ἡ εἰς το\ ἀδύνατον ἀπαγωγή, reduction to the impossible): commonly called indirect proof.
napagogeIn mathematics, a progress or passage from one proposition to another, when the first, having been demonstrated, is employed in proving the next.
Webster's Revised Unabridged Dictionary
Gr. a leading away, fr. to lead away; from + to lead