Indian systems of philosophy have paid considerable attention to the problem of knowledge and the means of obtaining it. The object to be known is called ‘prameya’ (‘that which is measured or known’), the means of knowing it is ‘pramāṇa’ (‘the measure’) and the know-ledge obtained thus is ‘pramā’ (‘that which is measured’).
The pramāṇas accepted by the various schools vary from two to six. However, almost all the theistic schools are agreed on three of them and consider them as more basic. They are: pratyakṣa (direct perception), anumāna (inference) and āptavākya (testimony), the āgama or scriptural testimony being considered the highest in the last category.
When smoke is seen on a distant hill, though fire itself is not seen directly, we conclude that there is fire on the hill since smoke is invariably associated with fire. Here, the means of our know-ledge of fire on the hill is ‘anumāna’ or inference. We are measuring (mā = to measure) or knowing the object of know-ledge (fire), following (anu = to follow) a given premise (i.e., the smoke and the invariable concomitance of smoke with fire known to exist from our earlier experiences).
Some technical terms commonly used while defining anumāna are: ‘sādhya’ (what is to be proved; here, the fire), ‘hetu’ (the cause for such inference; here, smoke) and ‘pakṣa’ (that which takes a side, or causes doubts; here, the hill).
See also PRAMĀṆAS.