『三十頌』『性入法』の成立時期をめぐって：Thon mi sambhoṭaの生存年代

Tibetan traditions say that the thirty Tibetan characters were invented by Thon mi saṁbhoṭa, a minister under King Srong btsan sgam po, and that the same minister composed both Sum cu pa and rTags kyi ʼjug pa, works on Tibetan grammar.The clan name Thon mi occurs in Tibetan documents from Tun-huang, but the name of a minister， Thon mi saṁbhoṭa or Aanu’i bu, never does, either in the reign of Srong btsan sgam po or in later ones. There it is said only that the Tibetan characters originated at the time of Srong btsan sgam po.When compared to the contents of Sum cu pa and rTags kyi ʼjug pa, the Tibetan text of the stone pillar inscription of Zhol in Lhasa reveals some striking features, the most interesting of which is that the latter replaces ‘kyi’, the genitive particle explained in Sum cu pa, with ‘gyi’ in an places. Similar examples have been found in Tibetan documents from Tun-huang but are not conclusive as their dates are difficult to determine and they are prone to be affected by the scribes’ education. The stone pillar inscription, unlike them, preserves the text of a royal decree ensuring hereditary privileges for the descendants of Ngan lam stag sgra khong lod, thus reliable enough to prove that then ‘kyi’ was not yet in common use. On the other hand, rTags kyi ʼjug pa states the rule of accordance of particles as “a neutral (ma ning) suffix (rjes ʼjug) is followed by a final particle that is a neutral character (ming gzhi)”. This rule, which ceased to be widely adhered to after the adoption of new translation terms (skad gsar bcad), has left many examples in the inscription on the southern face of the Zhol stone pillar. Should Sum cu pa and rTags kyi ʼjug pa have been composed by one and the same person, they would fall between the end of the eighth century and 814. Other internal evidences show that Sum cu pa whose grammatical explanation is incomplete, is later than rTags kyi ʼjug pa. If we are to call the author of Sum rtags Thon mi saṁbhoṭa, he should be regarded not as the inventor of the thirty characters but as the composer of thirty ślokas…rTang kyi ʼjug consists of as many…sometime later than the reign of Khri srong lde brtsan, 742－797