Vyapti

(“pervasion”) In classical Indian philosophy, vyapti is the key condition determining the validity of an inference
(anumana). The accepted form of an
inference has three terms: An assertion
(pratijna) containing the thing to be
proved, a reason (hetu) containing
evidence to support the assertion, and
supporting examples (drshtanta). In
the stock example “there is fire on
the mountain, because there is smoke
on the mountain,” the assertion is
that there is fire, and the reason is that
there is smoke—with the underlying
assumption that smoke invariably
accompanies fire. In a valid inference,
the reason accounts for every case of
the thing to be proven; vyapti, or pervasion, is the term for this invariable
association between cause and effect.
For further information see Karl H.
Potter (ed.), Presuppositions of India’s
Philosophies, 1972.