The Vaiśeṣika philosophy is a naturalist school; it is a form of atomism in natural philosophy. It postulated that all objects in the physical universe are reducible to paramāṇu (atoms), and one's experiences are derived from the interplay of substance (a function of atoms, their number and their spatial arrangements), quality, activity, commonness, particularity and inherence. Knowledge and liberation was achievable by complete understanding of the world of experience, according to Vaiśeṣika school . The Vaiśeṣika darśana is credited to Kaṇāda Kaśyapa from the second half of the first millennium BCE. The foundational text, the Vaiśeṣika Sūtra, opens as follows,