In this chapter, Maimonides speaks as a scientist to remind the reader that while some astronomical questions are a matter of settled proof — “e.g., it has been proved that the path of the sun is inclined against the equator; this cannot be doubted” — others are the subject of what we might call scientific speculation.

But it has not yet been decided whether the sphere of the sun is excentric or contains a revolving epicycle, and the astronomer does not take notice of this uncertainty, for his object is simply to find an hypothesis that would lead to a uniform and circular motion of the stars without acceleration, retardation, or change, and which is in its effects in accordance with observation. He will, besides, endeavour to find such an hypothesis which would require the least complicated motion and the least number of spheres.

Of the two competing theories: excentricity or epicycles, Maimonides prefers the former to the latter because it is ‘the least complicated’ of the hypotheses on offer. Similarly, one could posit for the sake of simplicity a model which assigns to all the fixed stars a single revolving sphere; Maimonides himself does as much in the previous chapter.

It is, however, not impossible that the stars should have each its own sphere, with a separate centre, and yet move in the same way… Nevertheless the species of the stars can be numbered, and therefore we would still be justified in counting the spheres of the fixed stars collectively as one, just as the five spheres of the planets, together with the numerous spheres they contain, are regarded by us as one.

He also includes a side discussion about a threefold division of the Creation:

  1. “the pure Intelligences”
  2. “the bodies of the spheres endowed with permanent forms”
  3. “the transient earthly beings, all of which consist of the same substance”

A process of emanation is described in which each of the three aspects of creation:

the ruling power emanates from the Creator, and is received by the Intelligences according to their order: from the Intelligences part of the good and the light bestowed upon them is communicated to the spheres, and the latter, being in possession of the abundance obtained of the Intelligences, transmit forces and properties unto the beings of this transient world.

Lastly, he includes a moving discussion which seeks to claim these philosophical truths for ‘his people’:

these theories are not opposed to anything taught by our Prophets or by our Sages … But when wicked barbarians have deprived us of our possessions, put an end to our science and literature, and killed our wise men, we have become ignorant; this has been foretold by the prophets, when they pronounced the punishment for our sins: “The wisdom of their wise men shall perish, and the understanding of their prudent men shall be hid” Isaiah 29:14. We are mixed up with other nations; we have learnt their opinions, and followed their ways and acts … Having been brought up among persons untrained in philosophy, we are inclined to consider these philosophical opinions as foreign to our religion, just as uneducated persons find them foreign to their own notions. But, in fact, it is not so.

Commentary Maimonides shows remarkable persipcacity in his approach to scientific theories and their relation to observation. Astronomical observations can be fit into one of several possible theoretical frameworks, between which there was much scientific debate. In the geocentric understanding which prevailed at the time, many observed phenomena required the positing of either epicycles or eccentric rotation; Maimonides is aware that while both models may come close to describing and predicting astronomical phenomena, it is preferable to choose the “least complicated” one; in other words, Occam’s Razor. His further discussion about the number of the spheres to be ascribed to the fixed stars shows, further, that he is aware that one may choose to use two different descriptions (essentially, two different scientific theories) based on what aspect of the natural world one is trying to describe or predict.