Format change is that same as last week. The A reference are those arguments in favor of things existing eternally, and the B reference are Thomas’s refutations. I’m highlighting only the most interesting arguments on both sides, else (again) this post would run to 4,000 words.
A For things which have no potentiality to non-being, cannot possibly not be. Now there are some creatures in which there is no potentiality to non-being. For there cannot be potentiality to non-being except in those things which have matter subject to contrariety: since potentiality to being and to non-being is a potentiality to privation and form, of which matter is the subject; and privation is always connected with the opposite form, since it is impossible for matter to be without any form at all. But there are certain creatures in which the matter is not subject to contrariety: either because they are entirely devoid of matter; for instance intellectual substances, as we shall show further on, or because they have no contrary, as heavenly bodies, and this is proved by their movement, which has no contrary. Therefore it is impossible for certain creatures not to exist: and consequently it is necessary that they exist always.
B For the necessity of being that we find in creatures, from which the first argument is taken, is a necessity of order, as was shown above: and a necessity of order does not compel the subject of a like necessity to have been always, as we proved above. For although the substance of heaven, through being devoid of potentiality to non-being, has a potentiality to being, yet this necessity follows its substance. Wherefore its substance once brought into being, this necessity involves the impossibility of not being: but it does not make it impossible for the heaven not to be, from the point of view where we consider the production of its very substance.
Notes In A it is true that “it is impossible for matter to be without any form at all” and that “intellectual substances” are “entirely devoid of matter”, but that does not mean, as B says, that the forms and intellectual substances were themselves not brought into being.
A Again. If time is everlasting, movement must be everlasting, since it is the reckoning of movement: and consequently movables must be everlasting, since movement is the act of a movable. Now time must needs be perpetual. For time is inconceivable without a now: even as a line is inconceivable without a point. But now is always the end of the past and the beginning of the future, for this is the definition of the now. Wherefore every given now has time preceding it and following it: and consequently no now can be either first or last. It follows therefore that movables which are created substances are from eternity.
B Also the fifth argument, taken from time, supposes rather than proves the eternity of movement. For since before and after and continuity of time are consequent upon before and after and continuity of movement, according to the teaching of Aristotle, it is clear that the same instant is the beginning of the future, and the end of the past, because in movement there is something assignable that is the beginning and end of the various parts of movement.
Wherefore it will not be necessary for each instant to be thus, unless every assignable instant that we conceive in time be between before and after in movement, and this is to suppose that movement is eternal. But he who supposes that movement is not eternal, can say that the first instant of time is the beginning of the future, and the end of no past. Nor is it incompatible with the succession of time, if we place therein a now that is a beginning and not an end, because a line in which we place a point that is a beginning and not an end, is stationary and not transitory; since even in a particular movement which also is not stationary but transitory, it is possible to designate something as only a beginning and not an end of movement: for otherwise all movement would be perpetual, which is impossible.
Notes As B notes, A merely states without proof “movables must be everlasting”. And most important: time can have a beginning, movements can have a start.
A Moreover. If a thing is not in the same state now and before, it must be, in some way, changed, for to be moved is not to be in the same state now as before. Now everything that begins to be anew, is not in the same state now as before. Therefore this must result from some movement or change. But every movement or change is in a subject, for it is the act of a movable. Now, since movement precedes that which is made by movement, for movement terminates therein, it follows that before anything made there pre-exists a movable subject. And since this cannot go on indefinitely, we must necessarily come to some first subject that begins not anew but always has been.
B The early natural philosophers had no conception of such a making, for it was their common opinion that from nothing naught is made. Or if any of them conceived the idea, they did not consider that the name of making was applicable thereto, since the word making implies movement or change, whereas in this origin of all being from one first being, the transformation of one being into another is inconceivable, as we have proved. For which reason neither does it belong to the natural philosophers to consider this same origin of things, but to the metaphysician, who considers universal being and things that are devoid of movement. We, however, by a kind of metaphor transfer the name making even to that origin, so that we say that anything whatsoever is made, if its essence or nature originates from something else.
Notes From nothing naught is made, hence there has to be a cause why there is something rather than nothing.
A Again. Whatever begins to be anew, it was possible, before it was, that it would be. For if not, it was impossible for it to be and necessary for it not to be: and so it would always have been a non-being and it never would have begun to be. Now that for which it is possible to be is a subject potentially a being. Therefore before everything that begins to be anew, there must pre-exist a subject which is a potential being. And since this cannot go on indefinitely, we must suppose some first subject which did not begin to be anew.
B Wherefore it is clear that neither is the second argument cogent, which was taken from the nature of movement. For creation cannot be described as a change save metaphorically, in so far as the created thing is considered to have being after non-being: in which way one thing is said to be made out of another, even in those things where the one is not changed into the other, for the sole reason that one succeeds the other, as day out of night.
Nor does the nature of movement that is brought into the argument justify the conclusion (since what nowise exists is not in any particular state) that when it begins to exist, it is in a different state now and before. Hence again it is evident that there is no need for a passive potentiality to precede the existence of all created being, as the third argument inferred. For this is necessary in those things which take their origin of being from movement, since movement is the act of a potential being.
But before a created thing was, it was possible for it to be, through the power of the agent, by which power also it began to be: or it was possible on account of the habitude of the terms, in which no incompatibility is found, which kind of possibility is said to be in respect of no potentiality, as the Philosopher says (5 Metaph.). For this predicate being is not incompatible with this subject world or man, as measurable is incompatible with diameter; and thus it follows that it is not impossible for it to be, and consequently that before it was, it was possible for it to be, apart from all potentiality. But in those things which are made by movement, it is necessary that they be previously possible in respect of a passive potentiality: and it is with regard to these that the Philosopher employs this argument (7 Metaph.).
Notes Reminder: A passive potency needs to actualized by something outside the thing. E.g., a thing coming into being because its created in some instant by God. An active potency is with respect to the thing itself. E.g., you now have the potential to walk away from your computer or device an enjoy this long weekend, a power which you can make actual. And I suggest you do so.