"A thing may be too sad to be believed or too wicked to be believed or too good to be believed; but it cannot be too absurd to be believed in this planet of frogs and elephants, of crocodiles and cuttle-fish."

There is one very fixed, and I think very false, conception current in human life--the conception that to laugh at a thing is in some strange way to score off it. The literature of blasphemy, for instance, always assumes that when a thing has been shown to be ridiculous, it has in some way been shown to be disgusting or untrue. So far from having been shown to be disgusting, it has not even been shown to be undignified; so far from having been shown to be untrue, it has not even been shown to be improbable. ... A thing may be too sad to be believed or too wicked to be believed or too good to be believed; but it cannot be too absurd to be believed in this planet of frogs and elephants, of crocodiles and cuttle-fish. The round earth itself is so round that it is impossible to say for certain that it is not standing on its head.

-April 18, 1903, Black and White
Quoted in The Man Who Was Orthodox" A Selection from the Uncollected Writings of G. K. Chesterton, collected by A.L. Maycock (1963)