The Collaborative International Dictionary
Apagogic \Ap`a*gog"ic\, Apagogical \Ap`a*gog"ic*al\, a.
Proving indirectly, by showing the absurdity, or
impossibility of the contrary.
--Bp. Berkeley.
Wiktionary
a. (alternative form of apagogic English)
Usage examples of "apagogical".
The apagogical proofs have, however, this advantage with regard to their evidence over direct proofs, that contradiction always carries with it more clearness in the representation than the best combination, and thus approaches more to the intuitional character of a demonstration.
In that case the rule applies, non entis nulla sunt praedicata, that is, everything that has been asserted with regard to an object, whether affirmatively or negatively, is wrong, and we cannot therefore arrive apagogically at the knowledge of truth by the refutation of its opposite.