| Quote #1
"Though I've never understood how God could expect his creatures to pick the one true religion by faith—it strikes me as a sloppy way to run a universe." (13.46)
Jubal doesn't necessarily disregard faith, but his inner rationalist finds the notion less than convincing or, at the very least, not fulfilling.
| Quote #2
But with bleak honesty Jubal admitted that the Fosterites might own the Truth, the exact Truth, nothing but the Truth. The Universe was a silly place at best… (14.109)
Not being able to know the truth means there is always the possibility that claims of truth that Jubal finds unconvincing might still be right. It's Jubal's "best to keep an open mind" philosophy at work.
| Quote #3
"Thou Art God," Mike repeated serenely. "That which groks. Anne is God. I am God. The happy grasses are God. Jill groks in beauty always. Jill is God. All shaping and making and creating together—" (14.180)
Mike's Martian heritage translates this as an answer for who or what is God. Very similar to pantheism, the idea is that God and the universe are identical, one and the same.