As a young student he easily distinguished himself by the translation of several philosophical, mathematical, and medical books from Arabic or Latin into Hebrew. King Robert of Naples, who was then living in the south of France, hearing of his proficiency, commissioned him to go to Rome and translate some Hebrew books into Latin for him. While Kalonymos was in Rome he was a great favourite with all who knew him intimately, and, owing to his fine appearance, his prominent position, and his manifold accomplishments, he had no difficulty in obtaining entry into the best Roman society. Several of his contemporaries, and more especially Immanuel di Roma, a friend of Dante, speak of him in high terms, and bestow upon him, too, his father's title of Nasi.
Whilst in Rome Kalonymos was asked by the leaders of the Jewish community of Avignon, where he and his parents had lived for some time, to come thither in order to take a petition to the Pope, who was then residing there, praying that he would exert his influence in favour of the Jewish inhabitants of Avignon, for whose extermination the Christian population had planned a secret plot. It is not known what the result was. Graetz, in his History of the Jews (vol. VII, p. 305), states that Kalonymos died about the year 1337, but he does not mention the place of his death.
Kalonymos's chief work is, by general consent, his Eben Bochan (“The Touchstone”), manuscripts of which are to be found in several libraries, including those of Munich, Leyden, Paris, and Florence. Printed as an editio princeps at Naples in 1489, a second edition appeared at Venice in 1558; it was subsequently published at Sulzbach in 1705, and again at Fürth (without a date), and also at Lemberg in 1865. In 1878 Dr. Kayserling edited the late Dr. Meisel's posthumous German translation in verse, to which he added a brief sketch in German of Kalonymos's life and principal works.
Among the scholars who have discussed the Eben Bochan may be mentioned Bartholocci, Wolf, Zunz, Geiger, Gross, Steinschneider, and Neubauer. It is pretty generally agreed that it was composed about the year 1324, that is to say, at a comparatively early period of the author's life. This theory is supported by the fact that it contains passages in which Kalonymos refers to his youth and unmarried state, and that its style is in many places marked by a singular freshness and vivacity which is seldom found in the writings of older men. The work is remarkable for its conciseness and epigrammatic force, and is further distinguished by the ingenuity with which Biblical and Talmudical phrases are woven into a kind of mosaic. It is somewhat similar in style to the Bechînath Olam, the author of which, Yedaya Bedaresi, was Kalonymos's contemporary. But while Bedaresi never failed to preserve the sternness and dignity peculiar to a moralizing philosopher, Kalonymos not infrequently relieved the seriousness of his narrative by flashes of humour and irony. He censures and ridicules the foibles of his Jewish contemporaries, but confesses at the same time, more in jest perhaps than in earnest, that he himself was not quite innocent of the same faults. One of the most humorous parts of the Eben Bochan is that at which the author makes merry over his own misfortune in being born a male child of Jewish parents. For as such he has during all his lifetime to bear the heavy yoke of the six hundred and thirteen precepts (תרי״ג מצוות), together with various other Talmudical restrictions. The following free translation will give an idea of the author's style and mode of expression:—
Oh, hapless sire, distraught with cares,
Whose wife to him male children bears,
For all of them, or rich or poor,
Have only suffering to endure;
This is caused by the Jewish creed,
Whose yoke is hard to bear, indeed.