That we may more easily perceive the Literal meaning of the first division, to which we now attend, it is requisite to know who and what are those who are summoned to my audience, and what is that third Heaven which I say is moved by them.

And firstly I will speak of the Heaven; then I will speak of those whom I address And although with regard to the truth concerning those things it is possible to know but little, yet so much as human reason can discern gives more delight than the best known and most certain of the things judged by the sense; according to the opinion of the Philosopher in his book on Animals.
I say, then, that concerning the number of the Heavens and their site, different opinions are held by many, although the truth at last may be found.

Aristotle believed, following merely the ancient foolishness of the Astrologers, that there might be only eight Heavens, of which the last one, and which contained all, might be that where the fixed stars are, that is, the eighth sphere, and that beyond it there could be no other.

Again, he believed that the Heaven of the Sun might be immediate with that of the Moon, that is, second to us.

And this opinion of his, so erroneous, he who wishes can see in the second book on Heaven and the World, which is in the second of the Books on Natural History.