Twain has a moment of questioned faith in Chapter 6. What inspires this questioning? Is he questioning his faith or the object? Why does he question at all?

Twain is brought to a Jesuit cathedral and shown what is purported to be the cross that Jesus was crucified upon. According to Twain, he isn't sure if the cross is genuine, but he has serious doubts because the cross is polished and looks new. His faith in God does not seem to be in questions, just his faith in man.