It defends the existence of God perfectly.
He actually dissects Aquinas' proofs quite well in this book.
I'll never fully understand why believers feel the need to defend the existence of God. I know God exists, and my human inability to prove his existence amounts to basically nothing. If more Christians were worried about their own walk with God, and less about arguing with atheists, we'd all be better off. Of all the conversions I've seen, including my own, not one came about because a Christian had a convincing argument.