 As is standard within the intellectual milieu dominated by Aristotelian physics, Israeli opined that the generation and passing away of terrestrial objects was the result of recombination of elements and their attendant properties (heat, coldness, wetness and dryness), a process which is governed by the movement of the cosmic sphere. Later thinkers would, via astrology, attribute certain roles in this process to the “intelligences” governing individual celestial objects and their relative positions. The heavens, which are not composed of the four elements and hence not affected by their contrary qualities, are not subject to generation and degeneration. (Isaac Israeli [Book of Definitions], p. 48)