‘If you argue with a madman, it is extremely probable that you will get the worst of it; for in many ways his mind moves all the quicker for not being delayed by the things that go with good judgment. He is not hampered by a sense of humour or by charity, or by the dumb certainties of experience. He is the more logical for losing certain sane affections.
Indeed, the common phrase for insanity is in this respect a misleading one. The madman is not the man who has lost his reason. The madman is the man who has lost everything except his reason . . . Now, speaking quite externally and empirically, we may say that the strongest and most unmistakable mark of madness is this combination between a logical completeness and a spiritual contraction. The lunatic’s theory explains a large number of things, but it does not explain them in a large way. I mean that if you or I were dealing with a mind that was growing morbid, we should be chiefly concerned not so much to give it arguments as to give it air, to convince it that there was something cleaner and cooler outside the suffocation of a single argument.’
~ G. K. Chesterton
G.K. Chesterton: An Appreciation by Mark Shea