Walter, God is science. God is polio and flu vaccines and M.R.I. machines, and artificial hearts. If you are a man of science, then that’s the only faith we need.
Except for our core characters, no scientist on Fringe was as consequential to the plot as Dr. Alistair Peck of MIT. Although he was the subject of an intense FBI investigation, he turned out to be one of Walter Bishop’s greatest friends… though, in strictly flat and linear time, Walter never met him.
Peck did not believe in a God beyond science. Yet, he either became God to Walter, or allowed God to speak to Walter through him, depending on how you view the meaning of his white tulip drawing.
His final actions foreshadowed the self-sacrifice that Walter Bishop had to make in order to save the world from the Observers. And like Alistair, Walter was able to send a message to Peter from the outside of time.
(BTW… here is a totally cool story from Peter Weller about how he came to guest star on Fringe. It’s a long story, but worth it!)