I have said that Asia and the ancient world had an air of being too old to die. Christendom has had the very opposite fate. Christendom has had a series of revolutions and in each one of them Christianity has died. Christianity has died many times and risen again; for it had a God who knew the way out of the grave. But the first extraordinary fact which marks this history is this: that Europe has been turned upside down over and over again; and that at the end of each of these revolutions the same religion has again been found on top. The Faith is always converting the age, not as an old religion but as a new religion. This truth is hidden from many by a convention that is too little noticed. Curiously enough, it is a convention of the sort which those who ignore it claim especially to detect and denounce. They are always telling us that priests and ceremonies are not religion and that religious organisation can be a hollow sham, but they hardly realise how true it is. It is so true that three or four times at least in the history of Christendom the whole soul seemed to have gone out of Christianity; and almost every man in his heart expected its end. This fact is only masked in medieval and other times by that very official religion which such critics pride themselves on seeing through. Christianity remained the official religion of a Renaissance prince or the official religion of an eighteenth-century bishop, just as an ancient mythology remained the official religion of Julius Caesar or the Arian creed long remained the official religion of Julian the Apostate. But there was a difference between the cases of Julius and of Julian; because the Church had begun its strange career. There was no reason why men like Julius should not worship gods like Jupiter for ever in public and laugh at them for ever in private. But when Julian treated Christianity as dead, he found it had come to life again.
-G. K. Chesterton, The Five Deaths of the Faith, On The Man Called Christ, The Everlasting Man, 1925
Read the rest of the section: The Five Deaths of the Faith
Read the lecture: The Everlasting Man