Referring to Odysseus’ speech that inspires, unifies, and invigorates the Greeks in Homer’s Iliad, from which Aristotle quotes in the final sentence of book Lambda, translator Joe Sachs says in a footnote, “Similarly, the divine intellect described by Aristotle does not create things or the world, but confers upon them their worldhood and thinghood” (Metaphysics, p. 252n). It is that which the what-it-is of every other thing presupposes. For Aristotle, the thought thinking itself identified with the first cause is the condition of their intelligibility, and the condition of the possibility of there being any intelligibility at all. Otherwise, everything would be in “chaos and night”.
For Aristotle, there could be no such thing as a beginning of time, nor could there be anything “before” time, since before and after presuppose time. The first cause and the stars persist forever, but to my knowledge he never clearly refers to anything being strictly eternal or outside of time altogether, as is true of God for Augustine.
Platonic forms might be outside of time, but Aristotle does not recognize forms of the Platonic sort. However, he says that the hylomorphic kind of form he does recognize is not itself subject to becoming or change. What becomes or changes is the composite of form and matter.
The first cause is also said to be exempt from becoming and change. We have recently seen, though, that Aristotle has a very specific concept of becoming and change. Any kind of new state — whether of body, soul, intellect, or knowledge — does not count for him as a becoming or a change.
The intuition behind this seems to be that becoming and change apply to processes that are continuous, whereas a new state may be considered to be something discrete. With composite things, he says that a new state may also be accompanied by a change or becoming in something else that is related to it.
The first cause, though, would be unaffected by anything else, so this would probably prevent its having a new state. Also, as a pure entelechy, it should always be in a state of completion or fulfillment, which would probably also rule out its having any new state. So while not technically eternal in the Augustinian sense of outside of time altogether, according to Aristotle it persists forever inside of time, without becoming or change, and it seems not to have any new states either.
The “firstness” of the first cause, then, does not refer to any kind of firstness in time. It is first in the sense that everything else has a dependency on it, while it has no dependency on anything else.
A puzzle related to the first cause is that it seems it is supposed to be both a pure that-for-the-sake-of-which, and a non-perceptible independent particular thing that persists forever. In general, we would not expect any particular thing to be a pure that-for-the-sake-of-which. But perhaps the thought thinking itself that he says characterizes the first cause is in fact a bridging term that could meet the conditions for both.
Thought thinking itself seems as if it may be the same as pure contemplation (theoria). In the Nicomachean Ethics, he says that contemplation seems more divine than human, and seems to feel a need to justify his claim that it applies to humans at all, but he associates it with what he considers to be the highest possible human virtue. As the highest possible virtue, it would qualify as an unconditional that-for-the-sake-of-which. If it is not just the idea of thought thinking itself but an actual thought thinking itself, then it is also a particular thing.
He also identifies it with the good and the beautiful, but this does not mean the Platonic idea of the Good as a logical universal that is supposed to have a univocal meaning. What gives it universal import is not logical universality, but its unique concrete relation to all other things. The concrete particular thing that is pure thought thinking itself is superlatively good and beautiful, just because it is a pure entelechy. A pure entelechy for Aristotle is itself the highest conceivable perfection, and is thus easily equated with the good and the beautiful in an unqualified sense.