God is what's good in me.
Johnny said this when he was six, and it says much about his life goal, which was also stated when he was young: to do some good for the world. Above his supreme intellect, Johnny has great humanity, wanting to help others as best he can. Yet this belief transcends mere altruism, and, as an agnostic (someone who does believe there is any proof of God's existence, but does not deny the possibility of said existence), Johnny wrestles with spirituality throughout his illness. He writes the "Unbeliever's Prayer" and tells God, if He exists, that he will "fight the good fight." Johnny does not need the existence of God to make him live a moral life; God is inside him, and he shares it with others.