“ It is very hard for a man to defend anything of which he is entirely convinced. It is comparatively easy when he is only partially convinced. ”
 G. K. Chesterton, Orthodoxy (1908). copy citation

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“But a key and a lock are both complex. And if a key fits a lock, you know it is the right key. But this involved accuracy of the thing makes it very difficult to do what I now have to do, to describe this accumulation of truth. It is very hard for a man to defend anything of which he is entirely convinced. It is comparatively easy when he is only partially convinced. He is partially convinced because he has found this or that proof of the thing, and he can expound it. But a man is not really convinced of a philosophic theory when he finds that something proves it.” source