The Two Fourth Councils

The Fourth Council is said to have been convened in the reign of the Kushan emperor Kanishka, around 100 CE at Jalandhar or in Kashmir. Theravada Buddhism had its own Fourth Council in Sri Lanka about 200 years earlier in which the Pali Canon was written down in toto for the first time. Therefore there are two Fourth Councils: one in Sri Lanka (Theravada), and one in Kashmir (Sarvastivadin).

It is said that for the Fourth Council of Kashmir, Kanishka gathered 500 monks headed by Vasumitra, partly, it seems, to compile extensive commentaries on the Abhidharma, although it is possible that some editorial work was carried out upon the existing canon itself. Allegedly, during the council there were all together three hundred thousand verses and over nine million statements compiled, and it took twelve years to complete. The main fruit of this Council was the compilation of the vast commentary known as the Mahā-Vibhāshā ("Great Exegesis"), an extensive compendium and reference work on a portion of the Sarvāstivādin Abhidharma.
Scholars believe that it was also around this time that a significant change was made in the language of the Sarvāstivādin canon, by converting an earlier Prakrit version into Sanskrit. Although this change was probably effected without significant loss of integrity to the canon, this event was of particular significance since Sanskrit was the sacred language of Brahmanism in India, and was also being used by other thinkers (regardless of their specific religious or philosophical allegiance), thus enabling a far wider audience to gain access to Buddhist ideas and practices. For this reason, there was a growing tendency among Buddhist scholars in India thereafter to write their commentaries and treatises in Sanskrit. Many of the early schools, however, such as Theravada, never switched to Sanskrit, partly because Buddha explicitly forbade translation of his discourses into Sanskrit because it was an elitist religious language (like Latin was in Europe in earlier times). He wanted his monks to use a local language instead; a language which could be understood by all. Over time however, the language of the Theravadin scriptures (Pali) became a scholarly or elitist language as well.