The assumption isn't "belief in God" though. The assumption is that God exists. What Zhai is saying is that you cannot assume something to be true, and then use that assumption to come up with a proof that the assumption is true.
Assumptions are either true or false, and the state of an assumption is unknown. You can use assumptions to learn things about certain other statements, but you cannot say anything about the truth value of the actual assumption.
Assumptions are either true or false, and the state of an assumption is unknown. You can use assumptions to learn things about certain other statements, but you cannot say anything about the truth value of the actual assumption.
