The chapter begins by introducing the origin of the Abhidharma and the structure of Abhidharma texts, focusing on the role of matrices, texts in question-and answer-format and the status of the omniscience of the Buddha in the development of the Abhidharma. It examines the question of the authenticity of the Abhidharma texts, followed by a discussion of five major Abhidharma schools: Mahāsaṃghika and the Sthaviranikāya schools, Theravāda, Pudgalavāda, Sarvāstivāda, and Sautrāntika. The section on Mahāsaṃghika contains discussion of its anticipation of Mahāyāna themes, the Theravāda section examines a key Abhidharma text, the Kathāvatthu, the Pudgalavāda discussion focuses on its conception of a person (pudgala) as distinct from a self, while Sarvāstivāda and Sautrāntika concentrate on the specific theories of time that differentiate these two schools.