“The Heaven of Saturn,” he says, “has two properties by which it may be compared to Astrology. The first is the slowness of its movement through the twelve signs; for, according to the writings of Astrologers, its revolution requires twenty-nine years and more. The second is, that it is the highest of all the planets. And these two properties are in Astrology; for in completing its circle, that is, in learning it, a great space of time passes; both on account of its demonstrations, which are more than in any of the above-mentioned sciences, and on account of the experience which is necessary to judge rightly in it. And, moreover, it is the highest of all; for, as Aristotle says at the beginning of his treatise on the Soul, Science is of high nobility, from the nobleness of its subject, and from its certainty; and this more than any of the above-mentioned is noble and high, from its noble and high subject, which is the movement of the heavens; and high and noble from its certainty, which is without any defect, as one that proceeds from a most perfect and regular source. And if any one thinks there is any defect in it, the defect is not on the side of the Science, but, as Ptolemy says, it comes from our negligence, and to that it should be attributed.”