As for the critical means to which I have alluded, the Gaon himself said somewhere that simplicity is the best criterion of truth, and this is the most characteristic feature of all his literary career. The Gaon studied Hebrew grammar in order to obtain a clear notion of the language in which the Scriptures are written. He tried to attain to the knowledge of the Bible by reading the Bible itself; and was not satisfied to become acquainted with its contents from the numerous quotations which are made from it in Rabbinical literature. Again, he studied mathematics, astronomy, and philosophy, as far as they could be found in Hebrew books. Certainly the Gaon did not study these subjects for their own sake, and they were considered by him only as a means to the end, or as the phrase goes, as the “hand‐maidens” of Theology, the queen of all sciences. But it may be looked upon as a mark of great progress in an age when Queen Theology had become rather sulky, continually finding fault with her hand‐ maidens, and stigmatising every attention paid to them as conducive to disloyalty. To these accusations the Gaon answered that Queen Theology does not study her own interests. Knowledge of all arts and sciences, the Gaon maintained, is necessary for the real understanding of the Torah which embraces the whole of them. From his own writings it is evident that he himself was familiar with Euclid, and his _Ayil Meshulash_ contains several original developments of Euclid. It was at his suggestion that a certain Baruch of Sclow translated Euclid into the Hebrew language.