 For the reasons just rehearsed, an eternal and unchanging First Mover entails an eternal and unchanging first thing moved, and observation suggests that this must be the outermost sphere of the stars, whose diurnal rotation in turn moves everything within its ambit: “there is a moved thing that is first by nature, which moves the whole, and which terminates every movement whose mover is external…. The mover of this [first] moved thing is, of itself, not a body and is absolutely and essentially unmoved” (EpiPhys 8.242 {141}). Past this first ceaseless motion, the causal story becomes increasingly complex, under the influence of the celestial intelligences. Ibn Rushd is suspicious of the unrealistic convolutions of Ptolemaic cosmology, preferring to honor the principles of Aristotelian physics even where that leaves a gap between theory and observation (Sabra 1984; Endress 1995). A strikingly personal remark describes how he had once aspired to close that gap, but has now, in his old age, abandoned the project (LongMeta XII.45 {1664}). Anticipating the modern rise of scientific specialization, he yields the field to those who devote themselves solely to this one science (LongMeta XII.48 {1679}).