 A significant part of The Sweets of Refutation is devoted to the question of whether various items in the Nyāya-Vaiśeṣika ontology can be satisfactorily defined. In the Aphorisms on the Vaiśeṣika System (Vaiśeṣika-sūtra), Kaṇāda (2nd century CE) offered an ontological scheme that included six positive categories (bhāva-padārtha-s), namely, substance (dravya), quality (guṇa), action (karma), universal (sāmānya), ultimate differentiator (viśeṣa), and the relation of inherence (samavāya). In Of the Seven Categories (Saptapadārthī), the later Vaiśeṣika philosopher Śivādityamiśra (12th century CE) added the negative category of absence (abhāva) to the list. This scheme of seven ontological categories was adopted by Nyāya-Vaiśeṣika philosophers like Udayana who combined this ontological scheme with the epistemological commitments of Nyāya. In the fourth chapter of The Sweets of Refutation, Śrīharṣa sets himself the task of dismantling this ontological scheme: he begins by attacking the notion of a positive category, and then attacks the definitions of substance, universal, ultimate differentiator, relation, and absence.