In classical Indian philosophy two Sanskrit words are used for the atom, the smallest impartite physical entity: "aṇu" and "paramāṇu." On the existence of such atoms, the classical Indian philosophers were divided. Among the orthodox Brahmanic schools, the Nyāya-Vaiśeṣika philosophers were the preeminent defenders of atomism, with the Mīmāṃsā philosophers as allies. On the opposite side, the Vedāntins denied atomism. Among the non-Brahmanic schools, the Jainas were clearly atomists, as were the Hinayana Buddhists. Yogācāra Buddhism, however, was strongly critical of atomism, and so too was Madhyamaka Buddhism.

The division of opinion on the issue thus cuts across the division between the Brahmanic and non-Brahmanic schools. Instead, the range of views about atomism more closely reflects the different schools' commitment to realism. After all, atomism is usually associated with a...