Rav Sherira Gaon רב שרירא גאון

The question was put by Rabbi Jacob ben Nissim of Kairouan. It was historical in substance: who followed whom, who wrote down what, why the Talmud looks the way it does.

The answer — the Epistle of Rav Sherira Gaon — is the only source of its kind written by a man inside the tradition and close in time to the events. Rav Sherira lists the generations of tannaim, amoraim and savoraim by name, explains what the savoraim added to the text, and names the heads of both academies in sequence over several centuries.

Almost everything known about the internal workings of the Babylonian academies and about how the Talmud was compiled comes from here. It is in no other source.

He himself headed Pumbedita for nearly forty years and passed the office to his son, Rav Hai. His end was hard: at ninety he was imprisoned on a denunciation together with his son, and their property was confiscated. He is reported to have lived to about a hundred.