"the reason why I don't believe"

"'I can tell myself now that my lack of belief is a final proof that the Church is right and the faith is true.  I had cut myself off for twenty years from grace and my belief withered as the priests said it would.  I don't believe in God and His Son and His angels and His saints, but I know the reason why I don't believe and the reason is—the Church is true and what she taught me is true.  For twenty years I have been without the sacraments and I can see the effect.  The wafer must be more than a wafer.'
     "'But if you went back . . .'
     "'If I went back and belief did not return?  That is what I fear, Mr Dunlop.  As long as I keep away from the sacraments, my lack of belief is an argument for the Church.  But if I returned and they failed me, then I would really be a man without faith, who had better hide himself quickly in the grave so as not to discourage others.'"

     Pierre Morin to Mr Dunlop, in Graham Greene's "A visit to Morin," in Graham Greene:  Complete short stories (New York:  Penguin Books, 2005), 262-263 (249-263).