And because, as has been said, this Lady was the daughter of God, the Queen of all, the most noble and most beautiful Philosophy, it remains to be seen who these Movers were, and what this third Heaven. And firstly of the third Heaven, according to the order which has been gone through. And here it is not needful to proceed to division, and to explanation of the letter, for, having turned the fictitious speech away from that which it utters to that which it means, by the exposition just gone through, this meaning is sufficiently made evident.
In order to see what is meant by the “third Heaven,” one has in the first place to perceive what I desire to express by this word Heaven alone: and then one will see how and why this third Heaven was needful to us. I say that by Heaven I mean Science, and by the Heavens “the Sciences,” from three resemblances which the Heavens have with the Sciences, especially by the order and number in which they must appear; as will be seen by discussing that word Third. The first similitude is the revolution of the one and the other round one fixed centre. For each movable Heaven revolves round its centre, which, on account of its movement, moves not; and thus each Science 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.