During his debate with Arif Ahmed and Andrew Copson at the Cambridge Union Society, Peter S. Williams gave a lucid illustration for the argument for the existence of God based on the contingency of material reality.[1]

Imagine if I asked you to loan me a book.  You say you don’t have it, but you’ll ask your friend to loan you his, and in turn you’ll loan it to me.  When you ask your friend for the book, he says he does not have it, but he’ll ask his friend to borrow his copy, and in turn he’ll loan it to you, who will loan it to me.  If this process continues ad infinitum, I will never receive the book.  If I do receive the book it is because the process of requesting to borrow the book is not infinite, but temporally finite.  Somewhere down the chain of requests to borrow the book, someone actually had the book without having to borrow it from someone else.