Buddhist studies scholars Akira Hirakawa (1915–2002) and Bibhuti Baruah have expressed skepticism about the teacherstudent relationship between Mahākāśyapa and Ānanda. They have argued that there was discord between the two, as indicated in the early texts. Hirakawa has further hypothesized that Mahākāśyapa and Ānanda were co-disciples, with the same teacher being Gautama Buddha, so there would be no need for a transmission between the two. East Asian religion scholar Elizabeth Morrison cites a tract by the Zen scholar Qisong (1007–1072) about the tradition of patriarchs in Buddhism. He noted the problem of a transmission between co-disciples who are not master and student. He resolved the problem by comparing Mahākāśyapa and Ānanda to siblings who inherit according to birth order. Responding to Hirakawa's arguments, Silk further argues that the unilinear nature of the transmission made it impossible for both Mahākāśyapa and Ānanda to receive the transmission from the Buddha, so Ānanda had to receive the transmission from Mahākāśyapa instead.