Upadhi

(“obstruction”) In Indian logic, a counterexample that renders an inference
(anumana) invalid by showing that the
reason (hetu) given as evidence for the
initial assertion (sadhya) is not invariably true. For example, the inference
that “there is smoke because there is
fire” was judged invalid because of the
counterexample of the red-hot iron ball,
which was considered fiery but not
smoky. Since the red-hot iron ball was a
class of fiery things that did not smoke,
it showed that the reason given for the
inference did not account for every case
of the thing to be proved (sadhya)—and
thus raised the possibility that there
were other such cases as well. This
invalid inference fails the requirement
known as pervasion (vyapti), in which
the reason must account for every
possible case; this is critical for validity
in an inference. Needless to say, the
search for such counterexamples was an
essential part of Indian logic, since
one such example could discredit an
opponent’s argument. For further
information and elaboration, see
Karl H. Potter (ed.), Presuppositions of
India’s Philosophies, 1972.