Any agnostic or atheist whose childhood has known a real Christmas has ever afterwards, whether be likes it or not, an association in his mind between two ideas that most of mankind must regard as remote from each other; the idea of a baby and the idea of unknown strength that sustains the stars. His instincts and imagination can still connect them, when his reason can no longer see the need of the connection; for him there will always be some savor of religion about the mere picture of a mother and a baby; some hint of mercy and softening about the mere mention of the dreadful name of God. But the two ideas are not naturally or necessarily combined. They would not be necessarily combined for an ancient Greek or a Chinaman, even for Aristotle or Confucius. It is no more inevitable to connect God with an infant than to connect gravitation with a kitten. It has been created in our minds by Christmas because we are Christians; because we are psychological Christians even when we are not theological ones. In other words, this combination of ideas has emphatically, in the much disputed phrase, altered human nature. There is really a difference between the man who knows it and the man who does not.
-G. K. Chesterton, Orthodoxy, Part 2 Chapter 1