[page 46] The third historiographic genre is that of the Chos 'byung ("Origin of Buddhism"). The very first of such texts may have been the one written by the eleventh-century scholar Rong zom Chos kyi bzang po of which only a few fragments have surfaced so far.22 Although the reasons are still far from transparent, it is possible that with the proliferation of various doctrinal cycles a need was felt to place these in historical perspective and thereby legitimate them. In any case we find, starting with the twelfth century, an enormous upsurge of interest in Indo-Tibetan religious history in particular. Unfortunately, only a fraction of the potentially available literary corpus of such texts has been located and published to date. For, while those authored by the bKa' gdams pa masters Phya pa Chos kyi seng ge (1109-1169) and his student gTsang nag pa brTson 'grus seng ge have yet to be discovered, the earliest extant text belonging to this genre is the Chos la 'jug pa'i sgo ("Introduction to Buddhism") by the second Sa skya pa patriarch Master (slob dpon) bSod nams rtse mo (1142-1182), a work which he completed towards the end of 1167 or the beginning of 1168. The overall approach to its subject-matter and its architecture typifies many subsequent chos 'byung texts such as those by *lDe'u Jo sras, mKhas pa lDe'u and Bu ston Rin chen grub, but we do not know whether he was indebted for these to his teacher Phya pa. His work was succeeded by the magnificent text of Nyang ral's chos 'byung which, however, bears little resemblance to it in terms of its scope and structure. bSod nams rtse mo's text deals in the main with the life of the Buddha, while Nyang ral principally deals with the religious environment of Tibet's imperial period. The thirteenth century, too, knew of a considerable number of such treatises, the sole information concerning which is owed to a very brief remark by Bu ston as well as potentially to a number of quotations in his own chos 'byung. He notes the existence of such treatises by Khro phu lo tsā ba Byams pa'i dpal (1172/73-1236), Chag lo tsā ba Chos rje dpal (1197-1264) and mChims Nam mkha' grags (1210-1285) to which he apparently had access when writing his own well-known work sometime between 1322 and 1326. The present whereabouts of these treatises, if they are still extant, is unknown. As few as two bona fide chos 'byungs that probably belong to this century have come down to us, namely those by *lDe'u Jo sras and mKhas pa lDe'u. Ne'u Paṇḍita Grags pa smon lam blo gros' sNgon gyi gtam[page 47] me tog phreng ba ("An Account of the Past, A Garland of Flowers") of 1283 (Chab spel, NE'U), while often referred to as a chos 'byung, styles itself in the introductory lines as a rgyal rabs. There is much in the manner in which the subject-matter is treated that is strongly reminiscent of a chos 'byung, so that we may characterize it as a text that falls midway between these two other genres.23