Joseph's reputation rests, however, not on his rabbinical knowledge or his poetical abilities, but on his activity in the field of religious philosophy. In a short treatise written in Arabic (the title being probably "Al-'Alam al-Saghir") and, according to Moritz Steinschneider, translated by Nahum ha-Ma'arabi into Hebrew under the title "Olam Katan", he expounds his views on the most important problems of theology. Though not an original thinker (at every point of his system he borrows very largely from Solomon Ibn Gabirol's "Fons Vitæ"),