PHYSICS

The text begins by describing celestial movements related to the poles.
...ascending indeed to the highest the primum mobile or first moving sphere as the wise man has declared, but [it proceeds] from the highest circle and from them is the motion from the mover of the highest. For the motions of the spheres are upon their own poles, and the poles are indeed the two extremities of the axis of the heaven; or they do not require an axis upon which they might move, as is the case with artificial things. Therefore, they move upon the place of fixed poles, or the axis which is in the orb itself. Therefore, the diversity of their motions is from the diversity of the poles, not from the diversity of the centers, and this is manifest of itself.

It is clear that any sphere necessarily has motion upon its own poles, and by this motion, it is distinguished from other spheres and surrounded by the higher one. If it were not so, then both would be the same sphere, and it would not be true that the spheres have two designated poles, nor would they have motion upon them. And since they would not have motion upon them, it would be ridiculous, and then the poles would exist for it in vain. Therefore, it is impossible to posit a sphere that does not have motion upon its two poles, by which it is distinguished from the higher one surrounding it, and by that motion it is known and discerned from it. And when any sphere has motion upon its two poles and also another motion by which it follows the higher one in its motion, then there will perfectly be a diversity of motion of any of the spheres from its own motion upon its poles and also from its following the motion of the higher one and its own motion through it. Furthermore, these two motions or more are coupled in the same sphere and mixed, and through this composition its motions are diversified, and the declinations of the planets from one another are diversified.

And since they discovered that they change the locations of the two equinoctial points with the circle of the sun's declination, they established from this two translations of the two poles of the orb of signs the zodiac around the poles of the equinoctial, and it seemed to them that the distance between the two poles of the orb of signs and the poles of the diurnal motion is not always toward the same part. We have already said that this sphere, called the orb of signs, is positive, and it is a circle upon which, and outside of which, the planets are here and there, and sometimes they approach it and sometimes they move away from it, and this is true and is found in any of them, and we have already said the cause of this thing. This circle, called the orb of signs, is designated by the sun in its motion, as Ptolemy said, and since it is positioned with respect to it as we have said, the other planets sometimes move upon it and sometimes to its two sides. The declination of any planet from this circle and the equinoctial is always of the same distance and limits.

However, the motion of the planets in the oblique circle and its two sides is established by them as being the motion of these planets according to the order of the signs, namely from west to east, contrary to the motion of the universe, for they saw, as we have said, that they move backward daily. But the Sun and Moon always move retrogradely; indeed, this motion is sometimes fast, sometimes slow, and sometimes moderate. The remaining five planets sometimes move forward, namely from east to west, and sometimes from west to east, and this is for the most part. And so they are called wanderers errantes planets, for they found two diverse motions for them, between which is a station, which is their existence in the same place for some days, and a direction, which is their motion toward the east. They called the motion that is with the motion of the universe a regression and an error. Along with this, they also found in each of them velocity and slowness, as in the sun and moon, for those motions conserve their regularity and measure, as we have said.

And because Ptolemy found these diverse motions for these planets, he sought out a theory for them by which their arrangement might be perfected, and from his position, the particulars are ordered and its revolutions can occur. He imagines according to this that which he applies regarding the causes of these diverse motions, and they are all coupled in one sphere of their spheres. And therefore the motions of any planet, with their diversity, are placed gathered in the substance of its sphere, and each of the seven spheres of the planets, according to his position, couples the number of spheres moving with diverse motions. All indeed are of diverse centers, and all move upon their centers, not upon poles, and each moves with its own motion proper to itself, one entering into the other, and their gathering is a sphere in itself; and with this...