I have been reading a recently published book about the existence of all things (e.g. addressing the question, "Why is there something rather than nothing?"), and am struck by an interesting issue I see in the book and others like it. The author interviews philosophers (among other professionals) who often speak about the existence of things based on what one can imagine (e.g. one imagining something about possible worlds). It seems to me that there should be some kind of theory about how thoughts relate to the universe before anyone can conclude things about its nature. I know there are philosophers who have raised the question that the "laws" that govern thought/logic may be very different than the physical laws that govern the universe (and hence whatever theories we have about the world may be nothing more than our own ideas); so why is there such emphasis placed on imagination when discussing metaphysical issues? Why is the intelligibility of an idea about the universe (e.g. whether there are many universes) a criterion for determining the truth-value of the idea? Perhaps another way to say this is: why is the way we think about things somehow a true representation of how things are? Is it because this is about all we can ultimately do in philosophy (as opposed to, say, science)?

You asked, among other things, "Why is the intelligibility of an idea about the universe...a criterion for determining the truth-value of the idea?" I wouldn't say that an idea's being intelligible to us is a criterion for its being true: that would be thinking too highly of ourselves! But an idea's being intelligible to us is necessary for our determining (i.e., ascertaining) its truth-value and even for our entertaining the possibility that it's true. If an idea is unintelligible to us -- if we can't make any sense of it -- then we can't make sense of the assertion that the idea is true, or even possibly true, or false, or even possibly false. I think we can understand the claim that some unspecified aspects of reality are unintelligible to us. But we can't understand the suggestion that some particular unintelligible claim about reality might be true (or false, for that matter). That limitation applies to science just as much as to philosophy.

I suspect that the book you're reading is Jim Holt's Why Does the World Exist? If you're interested in a more scholarly approach to the question "Why is there something rather than nothing?" you might check out Tyron Goldschmidt's edited collection of essays, The Puzzle of Existence (Routledge, 2013). For what it's worth, I think the question is defective when construed in the way it's typically intended, as I try to show in my contribution to the collection.

Read another response by Stephen Maitzen
Read another response about Existence, Mind