In this chapter, Maimonides explains the arguments used by Aristotle to prove the eternity of the Universe. It is clear that Maimonides considers him to be the philosopher par excellence because he says

No notice will be taken of the opinion of any philosopher but that of Aristotle; his opinions alone deserve to be criticized, and if our objections or doubts with regard to any of these be well founded, this must be the case in a far higher degree in respect to all other opponents of our fundamental principles (من خالف قواعد الشريعه).

  1. An argument from the eternity of motion and time: if we assume that motion had a beginning, then how did the ‘first’ motion start? Either one would have to posit a ‘first’ motion that was itself eternal, or we would need an infinite chain of causes. Similarly, since time is a measure of motion, time also is eternal.

  2. The First Substance (مادة الأولى) common to the four elements is eternal. For if it had a beginning it would have come into existence from another substance; it would further be endowed with a form, as coming into existence is nothing but receiving Form. But we mean by “First Substance” a formless substance; it can therefore not have come into existence from another substance, and must be without beginning and without end.

  3. The heavenly substance (which for Aristotle was a fifth type of matter) performs circular motion rather than the rectilinear motion of the four sublunary elements. Therefore, unlike the four elements of our experience, the heavenly substance “contains no opposite elements” and “whatever is destroyed, owes its destruction to the opposite elements it contains”. Hence, the heavens are indestructible and therefore they must be eternal. Maimonides points out that Aristotle therefore assumes a ‘one-to-one and onto’ correspondence between indestructability and not-having-a-beginning.

  4. When the Universe did not yet exist, its existence was either possible or necessary, or impossible. If it was necessary, the Universe could never have been non-existing; if impossible, the Universe could never have been in existence; if possible, the question arises, What was the substratum of that possibility? for there must be in existence something of which that possibility can be predicated. This is a forcible argument in favour of the Eternity of the Universe.

  5. If God produced the Universe from nothing, He must have been a potential agent before He was an actual one, and must have passed from a state of potentiality into that of actuality–a process that is merely possible, and requires an agent for effecting it

  6. If an agent is active at one time and inactive at another, this reflects (for ordinary agents) differences in circumstances which can be more or less favorable for an intended action. But

    God is not subject to accidents which could bring about a change in His will, and i s not affected by obstacles and hindrances … it is impossible, they argue, to imagine that God is active at one time and inactive at another.

  7. Because “Nature is wise and does nothing in vain”, “this existing Universe is so perfect that it cannot be improved, and must be permanent; for it is the result of God’s wisdom”.
  8. An arugment from ‘commonsense’: “all people have evidently believed in the permanency and stability of the Unvierse (كل الناس يصرحون بدوام السماء و ثباتها)”, attributing to them the residence of God or other spiritual beings. Maimonides does not consider this to be a proof in the philosophical sense, but he says that arguments of this kind are offered “to support the results of his philosophical speculation by commonsense”.

Maimonides offers an additional argument against his own stated position of Creatio ex nihilo, without attributing it to Aristotle:

How could God ever have been inactive without producing or creating anything in the infinite past? How could He have passed the long infinite period which preceded the Creation without producing anything, so as to commence, as it were, only yesterday, the Creation of the Universe?