It must have been interesting, anyway, two mystics arguing about whose mysticism, (the agnostic one or the theistic one) is the right one.
Russel's mysticism, it seems to me, consits of the reification of "language," which he more or less worships. Copleston's is a more traditional mysticism, but he does hold some awful Platonic views. For example this quote from the debate:
Why something rather than nothing, that is the question? This is not a question, it is a kind of insanity. Existense (something) cannot be contingent. If it were, it would be contigent on .... But if you name anything it is contingent on, it is something. There cannot be nothing. The question is stupid.
If I had been Russel I would have asked Mr. Copleston, "why does God exist?" If this is not a legitimate question about God, it is not a legitimate question about "existence," (which it is not). The concept of contingent existence is false, and once it is admitted non-contingent existence (of anything, including God) is possible, the concept is denied, and with it, Coplestons's major premise.
(Note: this is about existence, not existents, about which the question "why" is still not legitimate, however, the question, "how," is quite alright.)
I'm sure you will not agree with my opinion here, but it's differences of opinion that are worth discussing. Wouldn't it be rather dull and uninteresting if everyone agreed on everything.
[By the way, I have read Copleston, including his three volume A History of Philosophy which I found "big" but somewhat less than objective.]
Hank