Hetu

(“reason”) In Indian philosophy, this is
an important part of formulating an
inference (anumana). In this context,
the word has two differing meanings,
one general, the other more obscure.
The accepted form for an inference has
three terms: a hypothesis (pratijna), a reason (hetu), and examples (drshtanta);
each of these three have their own constituent parts. In its most general sense, the
word hetu refers to the reason or evidence
that supports the assertion in the initial
hypothesis. For example, the hypothesis
that a mountain is on fire would be supported by the reason that there is smoke on
the mountain.
In a narrower sense, hetu can also
refer to the part of a reason that proves
the hypothesis. For example, if one
proves the statement “the mountain is
on fire” with the reason “the mountain
has smoke,” the part of the reason that
indicates that there is smoke is the hetu.