I will prove to you that God exists

[Sheldon]

In the book you refer to he fields the hypothetical that universe had to be as it is. He rebuts the hypothesis because it begs the question why if a universe has to be in a certain configuration, why is it the narrow configuration that causes planets, star, galaxies, molecules and ultimately life to exist. It doesn't solve the problem only pushes it back. That's why he continues to believe in multiverse theory.

The puzzle is not with why we have a universe configured for planets and stars and life and all that. The puzzle is simply with why the universe is configured a particular way, regardless of what it leads to. Even if it were established that God exists, the puzzle still remains. Why this universe rather than another?

Multiverse views provide a potential answer to this puzzle by simply suggesting that this universe is just one of many universes out there, which does away with the puzzling aspect of a seemingly arbitrary configuration of a lone universe.

@Drew_2013 Note the word I have enlarged, think carefully, and if you're able objectively and critically about what this means, and why. It's a clue as to why the "fine tuning" religious argument, is weak and poorly reasoned.