Obversion
Obversion (ob*vẽr"shun) , noun
[Latin obversio a turning towards.]
1.
The act of turning toward or downward.
2.
(Logic) The act of immediate inference, by which we deny the opposite of anything which has been affirmed; as, all men are mortal; then, by obversion, no men are immortal. This is also described as “immediate inference by privative conception.” — Bain