Likewise, with regard to the fixed stars’ being in the eighth sphere, they claimed to know this because those stars never eclipse anything, whereas other bodies may eclipse them; and as for the spheres that carry them, they inferred their existence from the observed motions.

Knowledge of the exact speed of those motions, of the mutual eclipsing of some bodies by others, and the like, rests entirely on observation. At best it comes down to a few individuals who witnessed something and then related it to others; it is not established by mass-transmitted reports, but for the most part by solitary ones. Observational error, moreover, is well known. Because of this, the observations of the early and the later astronomers differ over the motion of the fixed stars: do they cover one celestial degree every one hundred years, or every sixty-six and two-thirds years, as was asserted by the Maʾmūnian observers? When the students of celestial configuration informed them of the motion of the sphere, they took that as evidence that the sphere possesses a soul which moves it by volition, for its movement is circular and therefore, they said, not natural. From the nine spheres they inferred nine souls, and from the nine spheres together with a tenth intellect they deduced ten intellects, the tenth being the first entity to emanate from the Necessary Existent. They further claimed that the sphere moves in imitation of the First Cause so that the potentialities and dispositions within it might be brought forth. The ultimate goal of philosophy, in their eyes, is to resemble the First Cause to the extent possible; this, they say, is the divine science—first philosophy and the supreme wisdom—yet it rests on premises so feeble that this is not the place to spell them out.

The point is that their system is built upon propositions that some people advance on the basis of intuitive surmise. When they admit that, in such matters, no demonstrative proof can be produced against an opponent, and that their physical propositions rest on what some people transmit from experiments, then if there is no proof in either domain, they possess no demonstration for what is distinctive to them. As for what they share with the rest of mankind, that is not attributable to them, nor is it part of their special science. Where, then, is the demonstration for the philosophical sciences—especially since the customary regularities that constitute the bulk of their universal sciences are liable to fail, as we have explained elsewhere? We know that in most of what they claim to possess demonstratively, they have no certain proof; nevertheless, we shall mention some of their inconsistencies.