But if the above is the gist of the traditions, the position described is not clear. The council is recognized by Mahayanists yet it appears to have resulted in the composition of a Sarvâstivâdin treatise, and the tradition connecting the Sarvâstivâdins with the council is not likely to be wrong, for they are recognized in the inscription on Kanishka's casket, and Gandhara and Kashmir were their headquarters. The decisions of councils are often politic rather than logical and it may be that the doctors summoned by Kanishka, while compiling Sarvâstivâdin treatises, admitted the principle that there is more than one vehicle which can take mankind to salvation. Perhaps some compromise based on geography was arranged, such as that Kashmir should be left to the Sarvâstivâdin school which had long flourished there, but that no opposition should be offered to the Mahayanists elsewhere. The relations of the Sarvâstivâdins to Mahayanism are exceedingly difficult to define and there are hardly sufficient materials for a connected account of this once important sect, but I will state some facts about it which seem certain. It is ancient, for the Kathâvatthu alludes to its doctrines.[200] It flourished in Gandhara, Kashmir and Central Asia, and Kanishka's casket shows that he patronized it.[201] But it appears to have been hardly known in Ceylon or Southern India. It was the principal northern form of Hinayanism, just as the Theravâda was the southern form. I-Ching however says that it prevailed in the Malay Archipelago. Its doctrines, so far as known, were Hinayanist but it was distinguished from cognate schools by holding that the external world can be said to exist and is not merely a continual process of becoming. It had its own version of the Abhidharma and of the Vinaya. In the time of Fa-Hsien the latter was still preserved orally and was not written. The adherents of this school were also called Vaibhâshikas, and Vibhâshâ was a name given to their exegetical literature. But the association of the Sarvâstivâdins with Mahayanists is clear from the council of Kanishka onwards. Many eminent Buddhists began by being Sarvâstivâdins and became Mahayanists, their earlier belief being regarded as preliminary rather than erroneous. Hsüan Chuang translated the Sarvâstivâdin scriptures in his old age and I-Ching belonged to the Mûlasarvâstivâdin school;[202] yet both authors write as if they were devout Mahayanists. The Tibetan Church is generally regarded as an extreme form of Mahayanism but its Vinaya is that of the Sarvâstivâdins.