「仮設とその根拠」を巡る思想展開 : 『菩薩地』から『顕揚聖教論』へ

The purpose of this paper is to show how the concepts of prajñapti (“the conventional designation”) and nimitta (“the causal basis”) have been developed in the Yogācāra school. In his Xian yang sheng jiao lun 顕揚聖教論VII 10, Asaṅga (ca. 330–405) formulates an argument to prove the existence of the dependent nature (paratantrasvabhāva) of things from the viewpoint of the Yogācāra theory. On the grounds that the conventional designation must have its causal basis, Asaṅga argues that there exists the dependent nature of things as it serves as the causal basis of the designation. The same idea is also expressed in the Tattvārtha Chapter 真実義品of the Bodhisattvabhūmi 菩薩地(ca. 230–300), which makes the point that a causal basis of the conventional designation is something that exists as a real entity (vastu). The idea refuted in both texts is that all the entities are the mere conventional designation (prajñaptimātram eva sarvam), which is quite often attributed to the Mādhyamika school. Furthermore, we notice that, in the Bodhisattvabhūmiviniścaya 摂決択分中菩薩地(ca. 350–380), a causal basis of the conventional designation is considered as that which arises in dependence on others (rten cing ’brel par ’byung ba). Accordingly, we may say that the concept of the causal basis, the germ of which is found in the Tattvārtha Chapter, is developed in the Bodhisattvabhūmiviniścaya and passed on to the Xian yang sheng jiao lun. Another point to notice is that the Mādhyamika scholar Bhāviveka (ca. 490–570), who criticizes the Yogācāra theory of the dependent nature by quoting the passage in question from the Xian yang sheng jiao lun, has in mind the arguments in the Tattvārtha Chapter. The idea Bhāviveka criticizes is that a causal basis of the conventional designation must be existent, which is commonly held by the Yogācāra scholars at that time.