nce moves round
its subject, which itself moves not; for no Science demonstrates its
own foundation, but presupposes that. The second similitude is the
illumination of the one and the other. For each Heaven illuminates
visible things; and thus each Science illuminates the things
intelligible. And the third similitude is the inducing of perfection
in the things so inclined. Of which induction, as to the first
perfection, that is, of the substantial generation, all the
philosophers agree that the Heavens are the cause, although they
attribute this in different ways: some from the Movers, as Plato,
Avicenna, and Algazel; some from the stars themselves, especially the
human souls, as Socrates, and also Plato and Dionysius the
Academician; and some from celestial virtue which is in the natural
heat of the seed, as Aristotle and the other Peripatetics. Thus the
Sciences are the cause in us of the induction of the second
perfection; by the use of which we can speculate concerning the Truth,
which is our ultimate perfection, as the Philosopher says in the sixth
book of the Ethics, when he says that Truth is the good of the
intellect. Because of these and many other resemblances, it is
possible to call Science, Heaven.

Now it remains to see why it is called the third Heaven. Here it is
requisite to reflect somewhat with regard to a comparison which exists
between the order of the Heavens and that of the Sciences Wherefore,
as has been previously described, the Seven Heavens next to us are
those of the Planets; then there are two Heavens above these, the
Mobile, and one above all, Quiet. To the Seven first correspond the
Seven Sciences of the _Trivium_ and of the _Quadrivium_,
namely, Grammar, Logic, Rhetoric, Arithmetic, Music, Geometry, and
Astrology. To the eighth Sphere, i.e., to the starry, correspond
Natural Science, which is termed Physics, and the first Science, which
is termed Metaphysics. To the ninth Sphere corresponds Moral Science;
and to the Quiet Heaven corresponds Divine Science, which is
designated Theology.

And the reason why this is, remains briefly to be seen. I say that the
Heaven of the Moon is likened unto Grammar because it is possible to
find a comparison to it. For if you look at the Moon well, two things
are seen to be proper to it which are not seen in the other stars: the
one is the shadow which is in it, which is no other than the rarity of
its body, in which the rays of the Sun can find no end