Sherira was a Gaon of the old school, who valued the Talmud above everything, and steered clear of philosophical ideas. He was sufficiently acquainted with the Arabic language to use it in answering questions which were directed to him by the Jewish communities in Moslem countries. He preferred, however, to make use of the Hebrew and Chaldee languages, and had no taste for Arabic literature. His literary activity was entirely devoted to the Talmud and cognate subjects. He did not trouble himself much about Biblical exegesis, but his moral earnestness makes us overlook his lack of higher culture. As a judge, he always endeavored to elicit the truth and to decide accordingly. As head of the school, he spared no pains to spread instruction far and near, hence his decisions are voluminous. But Sherira kept most conscientiously to Talmudic precedents in framing his decisions; and on one occasion severely criticised a master who taught his young slave the Bible, and when he had grown up, allowed him to contract an illegal marriage with another slave, because this was contrary to the decision of several Talmudical teachers. Sherira was versed in theosophy, which had but few followers at his time. Sherira is especially distinguished on account of his "Letter," which is the main authority for the history of the Talmudical, post-Talmudical, and Gaonic periods of Jewish history. Jacob ben Nissim (Ibn-Shahin), a pupil of the Chushiel who had been taken captive to Africa, and who taught the Talmud in Kairuan, sent a letter of inquiry in the name of the community of Kairuan to Sherira. In it the following questions were propounded: "In what way was the Mishna written down? If the traditional law is of remote origin, how does it happen that only authorities of a comparatively recent period are known to us as bearers of the same? In what order were the various books of the Mishna compiled?" Jacob also asked about the order of the Saboraim and the Geonim, and about their respective terms of office. Sherira wrote an answer (987) half in Hebrew and half in Chaldee, in which he threw light upon several dark portions of Jewish history. The chronicle of the Saboraim and Geonim as given by him is our guide for this epoch. Sherira in this "Letter" answers the questions put to him with the simple straightforwardness of the chronicler. But his opinions about the Exilarchs of the line of Bostanaï, and about some of his contemporaries, _e. g._, about Aaron Ibn-Sarjadu, are not altogether unbiased. We have to thank the Gaon Sherira for the preservation of the facts of Jewish history from the period of the conclusion of the Talmud till his own time. It was not in his power to produce an historical work of a critical character, nor, indeed, was this possible for the genius of the Middle Ages.