(“Particular”), one of the six orthodox systems (darshans) of Indian philosophy, significant for its naturalism, a feature that is not characteristic of most Indian thought. The Sanskrit philosopher Kaṇāda Kāśyapa (2nd–3rd century AD?) expounded its theories and is credited with founding the school. Important later commentaries were written by Praśastapāda, Udayana, and Śrīdhara.

After a period of independence, the Vaisheshika school fused entirely with the Nyāya (q.v.) school, a process that was completed in the 11th century. Thereafter the combined school was referred to as Nyāya-Vaisheshika.

The Vaisheshika school attempts to identify, inventory, and classify the entities and their relations that present themselves to human perceptions. It lists six categories (category) of being (padārthas), to which was later added a seventh. These are:

(1) dravya, or substance, the substratum that exist independently of all other categories, and the material cause of all compound things produced from it. Dravyas are nine in number: earth, water, fire, air, ether, time, space, spirit, and mind.

(2) Guṇa, or quality, which in turn is subdivided into 24 species.

(3) Karman (karma), or action. Both guṇa and karman inhere within dravya and cannot exist independently of it.

(4) Sāmānya, or genus, which denotes characteristic similarities that allow two or more objects to be classed together.

(5) Viśeṣa, or specific difference, which singles out an individual of that class.

(6) Samavāya, or inherence, which indicates things inseparably connected.

To these six was later added abhāva, nonexistence or absence. Though negative in content, the impression it makes is positive; one has a perception of an absence where one misses something. Four such absences are recognized: previous absence, as of a new product; later absence, as of a destroyed object; total absence, as of colour in the wind; and reciprocal absence, as of a jar and a cloth, neither of which is the other.

The Vaisheshika system holds that the smallest, indivisible, indestructible part of the world is an atom (aṇu). All physical things are a combination of the atoms of earth, water, fire, and air. Inactive and motionless in themselves, the atoms are put into motion by God's will, through the unseen forces of moral merit and demerit.