The Buddhist abhidharma traditions developed a more complex schematization of conditionality than that found in the early sources. These systems outlined different kinds of conditional relationships. According to K.L. Dhammajoti, vaibhāṣika abhidharma developed two major schemes to explain conditional relations: the four conditions (pratyaya) and the six causes (hetu).Dhammajoti, Bhikkhu K.L. (2009) Sarvāstivāda Abhidharma, p. 143. Centre of Buddhist Studies, The University of Hong Kong. The vaibhāṣika system also defended a theory of simultaneous causation.Dhammajoti, Bhikkhu K.L. (2009) Sarvāstivāda Abhidharma, pp. 162-163. Centre of Buddhist Studies, The University of Hong Kong. While simultaneous causation was rejected by the sautrāntika school, it was later adopted by yogācāra.Dhammajoti, Bhikkhu K.L. (2009) Sarvāstivāda Abhidharma, pp. 159-161. Centre of Buddhist Studies, The University of Hong Kong. The Theravāda abhidhamma also developed a complex analysis of conditional relations, which can be found in the Paṭṭhāna.Karunadasa, Y (2010). The Theravada Abhidhamma. Its Inquiry into the Nature of Conditioned Reality, p. 262. Centre of Buddhist Studies, The University of Hong Kong. . A key element of this system is that nothing arises from a single cause or as a solitary phenomenon, instead there are always a plurality of conditions giving rise to clusters of dhammas (phenomena). The Theravāda abhidhamma outlines twenty four kinds of conditional relations.Karunadasa, Y (2010). The Theravada Abhidhamma. Its Inquiry into the Nature of Conditioned Reality, pp. 264–265. Centre of Buddhist Studies, The University of Hong Kong. .
