天可汗の現實と理想 --擴大解釋された唐太宗の天可汗--

Abstract

It has been said that the Tang emperor ruled China as the Son of Heaven and the steppe as the Heavenly Qaghan. This interpretation takes the Heavenly Qaghan as providing the opportunity to rule North and Central Asia. Many scholars have examined the actual significance of the Heavenly Qaghan based on this premise. Others, in contrast, have disagreed, pointing out that the Heavenly Qaghan should not be overly emphasized. So a scholarly consensus on how Tang Taizong as Heavenly Qaghan should be understood has not been reached. Bearing this issue in mind, this article examines the reality of Taizong as Heavenly Qaghan. As a result of this examination, we see that the Heavenly Qaghan in 630 (Zhenguan 4), which has previously been regarded as important, was used exclusively between Taizong and the remainder of the Türks, and at this point it is impossible to link it to Tang rule over North and Central Asia. It has also been argued that Taizong was again enthroned as Heavenly Qaghan in 646 (Zhenguan 20), but an examination of historical sources makes clear that this interpretation itself cannot stand. Therefore, Taizong as Heavenly Qaghan was only a title used in relation to the remainder of the Türks. Why then has the title Heavenly Qaghan been over emphasized and seen as providing the opportunity to rule over North and Central Asia? It's because of the Tongdian (通󠄁典) written by Du Yu (杜佑). To develop his argument on frontier defense policy more persuasively, Du Yu idealized Taizong, situating him as the Heavenly Qaghan reigning supremely over the barbarians. Thereafter, people of the Tang tended to be influenced by Du Yu and described Taizong as the idealized Heavenly Qaghan found in the Tongdian. As a result, Taizong as Heavenly Qaghan deviated from reality, and he came to be seen as the idealized ruler reigning over the barbarians of North and Central Asia. Based on the results of this analysis, it is difficult to understand Tang Taizong as Heavenly Qaghan providing an opportunity for his domination of North and Central Asia. In addition, as already pointed out by previous scholarship, the Tongdian does not simply describe the history of the system, but also contains Du Yu's positions on policy matters. Therefore to accept uncritically what is written there about the Heavenly Qaghan is to accept Du Yu's idealized Heavenly Qaghan that deviates from reality, and when discussing Taizong as the Heavenly Qaghan, we must use the Tongdian with caution.