G. K. Chesterton, “Christianity and Rationalism” (1904, The Clarion), G. K. Chesterton, Collected Works, vol. 1, pp. 373 – 380.
The following argument for the truth of Christianity comes from the Blatchford controversies, a civil exchange between anti- and pro-Christians in the pages of Robert Blatchford’s Clarion, 1904, from which G. K. Chesterton’s contributions have been culled and published in vol. 1 of his Collected Works:
“The Secularist says that Christianity has  been a gloomy and ascetic thing, and points to the procession of austere or ferocious saints who have given up home and happiness and macerated health and sex. But it never seems to occur to him that the very oddity and completeness of these men’s surrender make it look very much as if there were really something actual and solid in the thing for which they sold themselves. They gave up all pleasures for one pleasure of spiritual ecstasy. They may have been mad; but it looks as if there really were such a pleasure. They gave up all human experiences for the sake of one superhuman experience. They may have been wicked, but it looks as if there were such an experience.” (375 – 6)
“It is perfectly tenable that this experience is as dangerous and selfish a thing as drink. A man who goes ragged and homeless in order to see visions may be as repellent and immoral as a man who goes ragged and homeless in order to drink brandy. That is a quite reasonable position. But what is manifestly not a reasonable position, what would be, in fact, not far from being an insane position, would be to say that the raggedness of the man, and the homelessness of the man, and the stupefied degradation of the man proved that there was no such thing as brandy.” (376)
“That is precisely what the Secularist tries to say. He tries to prove that there is no such thing as supernatural experience by pointing at the people who have given up everything for it. He tries to prove that there is no such thing by proving that there are people who live on nothing else.” (376)
“Again I may submissively ask: ‘Whose is the paradox?’ The frantic severity of these men may, of course, show that they were eccentric people who loved unhappiness for its own sake. But it seems more in accordance with commonsense to suppose that they had really found the secret of some actual power or experience which was, like wine, a terrible consolation and a lonely joy.” (376)
“Thus, then, in the second instance, when the learned sceptic says to me: ‘Christian saints gave up love and liberty for this one rapture of Christianity,’ I should reply, ‘It was very wrong of them. But, having some notion of the rapture of Christianity, I should have been surprised if they hadn’t.’” (376)