Are there any unmistakable outward signs in a person surrendered to God? Would he be cantankerous? Would he smoke?
I think of the advertisements for ‘White Smiles’ Tooth Paste, saying that it is the best on the market. If they are true, it would follow that:
(1) Anyone who starts using it will have better teeth;
(2) Anyone using it has better teeth than he would have if he weren’t using it.
But you can’t test it in the case of one who has naturally bad teeth and uses it, and compare him with [someone] who has never used tooth paste at all.
Take the case of a sour old maid, who is a Christian, but cantankerous. On the other hand, take some pleasant and popular fellow, but who has never been to Church. Who knows how much more cantankerous the old maid might be if she were not a Christian. and how much more likeable the nice fellow might be if he were a Christian? You can’t judge Christianity simply by comparing the product in those two people; you would need to know what kind of raw material Christ was working on in both cases.
"Answers to Questions on Christianity," God in the Dock (Eerdmans: 1970) 59.