WALTER: "Why, William? Why would you do this? What can you possibly hope to gain by destroying both universes?"
WILLIAM BELL: "Walter, this was all your idea! Peter died, twice. You hated god. 'What kind of god would cause so much suffering?', that's what you said. So much pain. You decided to create a universe that would operate by your rules. And then, when you realized that you were smart enough to do it, you got scared. You asked me to cut out a portion of your brain."