“Belief without doubt would not be required by an all-loving God, and it should not be worn as a badge of honor. … Anyone who does not occasionally worry that he may be a fraud almost certainly is. Nor does the worry absolve one from the charge; one may still be a fraud, just one who rightly worries about it on occasion. Likewise, anyone who does not occasionally worry that she is wrong about the existence or nonexistence of God most likely has a fraudulent belief.”