THEORICA

...its own nature, or by desire, to assimilate itself to it and join in its motion, although the poles of each of them are different from its poles, and the poles of each one of them are different from the poles of another. And each one of them has, upon its own poles, a motion proper to itself, and all move towards the direction of the motion of the universe, as will be declared later.

And what ought to be proposed here is that each of the seven orbs existing under the orb of the fixed stars follows it in the motion of that same orb of fixed stars, just as it follows the supreme orb in the diurnal motion, and it distributes that oblique motion to it, namely, the one distributed to the orb of the signs original: "orbi signorum"; referring to the zodiac. For the other orbs find it from the fact that their poles follow its poles, as will appear in its place. Wherefore, in their stars, a change of position from their places appears over the length of time, although it has been hidden and is not seen by the senses except through the length of time. And when this motion is mixed with the motion of each of the seven planets, its arrangement and locations will be changed, and it will be difficult to discern them from them. And sometimes one of them follows a superior one in motion, and there will not be knowledge and differentiation of these two motions—that is, the motion of the superior from the motion of the inferior—among us. Wherefore the motions appearing to us are mixed and commingled; thus it will be difficult or impossible to discern between them which motions of each of these orbs are proper to them. Even if they are mixed with another, it still preserves the order, and the following of one to another appears to the senses.

FURTHERMORE, we say that the better order which we ought to follow in this little book is to begin from the supreme orb, whose motion is simple, coming to that which is of lesser simplicity until the last, which is closer to us. And our beginning will be from the place of the beginning of motion, for from there motions are discerned, and we pursue them according to order. And it is not our intention in this discourse to bring in the measurements of motions, nor to reveal their other accidents, nor to dwell on their particularities and the calculations of motions perfectly, for that would require a length of discourse, more subtle speculation, and recent observation. But our intention is to declare the quality of those motions and to join them with their diversity in each of the orbs and their order, without digression from their nature, nor removal of the orbs from the circular motion found in them. Thus, let the center of all be the center of the universe, and let their natural motions be toward the part of the motion of the universe, and let the intention of all be to join with the supreme and to follow it, or to seek to approach its motion. And he who is closer in his motion to it, his arrival at the intended end will be more perfect, and his diminution from it will be lesser. And the arrival of him who is more distant will be lesser, and his defect greater.

A DISCOURSE on the orb that moves with universal motion: We say that the supreme orb moves upon two poles that are fixed, and its motion is from east to west in a single revolution in a day with its night, and it is the mover of the universe. Its motion is the swiftest of all motions existing under it, and all orbs that are under it fall short of this motion. And the space of the defect of each orb from the universal motion will be according to the space of its removal from that mover or according to the proximity to it. And each of the orbs existing under it desires to assimilate itself to it and moves following it according to the measure of its virtue attributed to it from the supreme, and preserves its form by the motion proper to itself by which it moves upon its own poles by another motion, following indeed the motion of the supreme and subjecting itself to that motion and assimilating itself to the supreme.

And the motions of the orbs existing under the supreme orb differ in their following motion regarding velocity and slowness according to proximity and removal from the supreme, for the virtue in motion is according to the measure of proximity to the mover from which the virtue emanates. And since the motion of the supreme, simple orb is simple and there is no change in it, therefore it is always in the same mode of velocity. And the orb succeeding it has of the simplicity of motion according to the measure of its proximity to the simple, and its virtue in motion is stronger and its velocity greater, for it proceeds from the supreme. And the body, by how much more removed it will be from that, by so much its virtue is weaker, wherefore...