  Abraham ibn Daud’s importance lies in the fact that he was the first to present a coherent systematic interpretation of Judaism in light of the new challenge, namely Muslim Aristotelianism. The sustained use of Aristotelian doctrines and logical reasoning clearly distinguishes ER from the writings of earlier Jewish philosophers. Moreover, the manner in which he incorporates his Muslim (and to a lesser extent) Jewish sources in a carefully structured system in order to solve a religious problem is noteworthy. His thought develops along the following lines: substance—form – motion and transition from potentiality into actuality—soul – God—intelligences—prophet—freedom of the will—correspondence between correct knowledge and correct conduct—perfection.