Dore on Rowe on the Cosmological Argument

I recently came across an old paper by Clement Dore, entitled "Rowe on the Cosmological Argument" (1983). In it, Dore objects attempts to uphold Hume's objection to the PSR, by critiquing Rowe's defense of the principle. He writes:

[In] order to support the cosmological argument, PSR must be interpreted this way: "For any infinite set, S, each of whose members can be explained by another member, the question 'Why are there any members of S?.' can (only) be truly answered by referring to a cause which is not itself a member of S." But how much credibility has PSR, thus interpreted? Consider the question, "Why are there any things which are at least as large as a quark?" Rowe's claim that PSR (as presently interpreted) may be plausible appears to commit him to the thesis that the following may be plausible: "If there is a finite number of members of the set of things which are at least as large as a quark (call it S'), then S' is like my philosophy of religion class, in that we do not need to infer an irreducibly distinct cause of its having members. However, if S' has an infinite number of members, then it is subject to a causal explanation which does not reduce to the individual explanations of the individual members, namely, the following one: The individual members of S' exist because there is something smaller than a quark which is their ultimate cause." 

But of course, Dore argues, it is absurd to suppose that there must be something smaller than a quark which is the ultimate cause of the set S'. And since PSR (allegedly) commits one to such a claim, it seems that PSR must be rejected.

I found this line of argument noteworthy, if only because of how absurdly weak it seems. Firstly, because the cosmological argument doesn't require one to assume any infinite set of objects; the argument from contingency (for example) works identically well whether the totality of all contingent things is finite or infinite.

But there's another issue with Dore's line of reasoning. For assuming that S' has infinitely many members, it seems that we may still avoid his claim of absurdity with relative ease. Example: suppose that the universe had a beginning in time, with an initial state and physical laws that were/are metaphysically necessary (this is the view taken by, among others, Graham Oppy). In that case, S' would be explained by the initial state of the universe, in tandem with the laws of nature that necessarily follow from it. This claim hardly seems absurd, and it is hard to believe that it should lead one to abandon PSR.

Alternatively, suppose that the universe has existed for eternity, and that its existence is metaphysically necessary. In that case, we have a number of options. For instance, S' might be metaphysically necessary (e.g. if the universe is necessary and past eternal, and S' includes everything in the universe, it follows that S' is metaphysically necessary). Alternatively, S' might be explained by the laws of nature in tandem with the most fundamental physical entities, and these things might be metaphysically necessary. Or else, if nothing in the physical universe is necessary, then S' would need to be explained by something outside of the universe, in which case the cosmological argument is sound. None of these options seem so absurd as the merit the rejection of PSR.

[Note: Dore might consider the last result (i.e. the cosmological argument being sound) to be absurd; however, this would hardly constitute a genuine reply to that argument. For then Dore would be arguing as follows: "The PSR as required by the cosmological argument is absurd, because if it were true, it would entail the success of the cosmological argument." This might be sufficient grounds for rejecting PSR, but it will certainly not convince anyone who regards the cosmological argument as sound.]