An infinite series of causes is possible only potentially, not actually. Even St Thomas admitted the possibility of an eternal cosmos, as long as it was acknowledged that God is the primary cause of such a thing. Bertrand Russell was such a mathematician that he assumed working with abstract infinite sets granted their existence in the actual world, indeed AS the actual world. This is, however, as erroneous as saying that because we can, semantically and mentally, "handle" unicorns, therefore they actually exist. He made much of this in his 1948 debate with Copleston, citing Japanese novels as a case of fictional causes having real effects. But even this point fails to see that God is beyond being in an analogously supreme way to fictional characters who do indeed have a sort of personal efficacy, just as lines have an oblique, extra-dimensional efficacy in forming lines in Riemann spaces. If God were MERELY another efficient cause, he would indeed be subsumable to the total causal matrix of the cosmos, as reified by Russell. But, in fact, God is the transcendent cause of both cosmic efficient causality and the coherence of the physical "set" that may someday describe the cosmos in toto.