Saadia was not the only Jew engaged in philosophy during the late ninth and early tenth century. He was rivaled by his near contemporary Isaac Israeli - philosopher and physician in Kairouan - who produced a very different literary corpus with strong ties not to Stoicism and Mu'tazilite kalam but to Neoplatonism. Each of Israeli’s surviving philosophical works includes discussions of the soul; a brief discussion of them will be given here.
Israeli’s Book of Definitions is Neoplatonic in form as well as content. Following the Alexandrian school tradition (and more directly its Arabic epigone al-Kindl), it presents a list of some 57 philosophical terms which are organized not alphabetically but conceptually. Following the definitions and descriptions of “philosophy” itself, he presents terms from above to below, according to their place within the cosmos: wisdom, intellect, soul, celestial sphere, sublunar, and celestial body.
The definitions given by Israeli are strongly metaphysical and generally fit into standard Neoplatonic emanationist cosmologies. Intellect is the first emanation or hypostasis, the specificality of all things and genus of genera; it knows itself and through knowing itself knows all other things; it is, however, of three types or stages: actual intellect; potential intellect; and a ‘‘second intellect’’ - which refers to the process of acquiring possible knowledge through sensation and experience, which can then be transformed into actual knowledge. Soul is second to intellect; it is a substance that perfects the body that possesses life potentially (according to Aristotle), or a substance connected with the celestial body (according to Plato).
After harmonizing these two views (following the standard Neoplatonic practice of harmonizing Plato and Aristotle), Israeli provides more detailed information about the different souls or types of soul, set in emanative order: The rational emanates from the intellect; it is highest in rank, is responsible for learning and knowledge in both the theoretical and practical spheres; it is because of the rational soul that one can receive reward or punishment. The animal soul is lower than the rational, from whose shadow it emanates; it is possessed by animals, is concerned primarily with sensation and movement, rather than reason and understanding; because animals cannot reason, they are not subject to reward and punishment. The lowest soul is the vegetative, which emanates from the shadow of the animal; it is concerned primarily with desire and governs the functions of nutrition, reproduction, growth, and decay. Contrary to humans and animals, vegetables are not in possession of reason, movement, or sensation.
The emanative scheme presented in The Book of Definitions is reproduced, with some variations, in The Book of Substances, The Chapter on the Elements, and The Book on Spirit and Soul. In these treatises Israeli’s ideas about soul and spirit are also sometimes explained in light of biblical terms and expressions. It is in his work where I Samuel 25:9 - ‘‘The soul of my Lord shall be bound in the bundle of life with the Lord thy God; and the souls of thine enemies, them shall he sling out, as from the hollow of a sling’’ - emerged as a popular biblical prooftext of both eternal reward and punishment for the soul, and where a Jewish eschatology is first developed out of Neoplatonic ideas and images. Like Saadia, Israeli combines biblical and rabbinic images with philosophy - in this case Neoplatonic philosophy - to create a striking image of the hereafter. For him, the soul is purified through good acts which correspond with reason, and is sullied by bad acts which are governed by the appetites of the animal soul. The pure soul is released into the spiritual realm, whereas the dark turbid soul remains below, caught in the cosmological sphere of fire, revolving eternally in this literal hell-fire.
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