What does the quote “To choose doubt as a philosophy of life is akin to choosing immobility as a means of transportation” from Life of Pi mean?

The quote in question appears at the very end of chapter seven, and it is one of my favorite quotes from the entire text.

I'll be honest about it. It is not atheists who get stuck in my craw, but agnostics. Doubt is useful for a while. We must all pass through the garden of Gethsemane. If Christ played with doubt, so must we. If Christ spent an anguished night in prayer, if He burst out from the Cross, "My God, my God, why have you forsaken me?" then surely we are also permitted doubt. But we must move on. To choose doubt as a philosophy of life is akin to choosing immobility as a means of transportation.

Pi is a wonderfully intelligent character, and he has one of the most unique perspectives on religion I have ever seen. He has found a way to incorporate Christianity, Islam, and Hinduism into his own personal belief system. For Pi, belief in something is important, and that opinion is further highlighted through his interactions with Mr. Kumar. Mr. Kumar is a strong atheist. Science, experimentation, logic, reason, and experience contribute to his faith.

There are no grounds for going beyond a scientific explanation of reality and no sound reason for believing anything but our sense experience. A clear intellect, close attention to detail and a little scientific knowledge will expose religion as superstitious bosh. God does not exist.

Pi definitely doesn't agree with Mr. Kumar, but Pi respects Mr. Kumar's stance. Kumar has chosen to believe in something. On the other hand, agnostics don't put their faith in anything, and that really bothers Pi. Agnosticism allows for the possibility of anything while at the same time doubting everything, and that really angers Pi. Agnostics have chosen not to believe in anything, which simply doesn't make any sense to Pi.