I am only going off of the video you linked to. Does Craig actually claim ” abstract objects do not really exist”? It seemed to me that his issue was that all abstract things necessarily begin in god and that Platonism implies abstract ideas are created ex nihilo, meaning something is created outside or beyond the purview of god’s will or essence. The necessity of Craig’s argument is, I believe, contingent on god’s existence as the distinction is unnecessary if there is no god.
I Think if he believed abstract objects didn’t exist he might have a difficult time explaining god. Where he explains Fictionalism, I believe, he was showing how abstractions are taken for granted as physical things or properties of physical things. It has been a few days since I watched the video but I recall him mentioning a brown dog. The dog exists physically and is made of physical things but what is brown? Brown is a property, and can be defined by not having any of the properties of another color but nowhere on earth can I locate a Brown. For that matter, take Donovan Bailey: He IS fast. That, and I think WLC would agree, is a perfectly useful statement. Like brown, fast is not a thing but the statement implies that “he” a physical thing “is” an abstract object “fast”
So, if I were to claim god does not exist because metaphysical things don’t exist in “reality” I would, in the least, have to greatly limit, what I consider, my understanding of the world and admit that most of speech is all baloney. That’s my take on this, anyway.
Professor Casey has requested that we send him a email to let him know when we make new posts you might shoot him one if you want to ensure his response.
p.s. I recall seeing mises 007 and you talking in the forum and I thought ” John Dee and 007, fancy that”