Most people, if they had really learned to look into their own hearts, would know that they do want, and want acutely, something that cannot be had in this world. There are all sorts of things in this world that offer to give it to you, but they never quite keep their promise. The longings which arise in us when we fall in love, or first think of some foreign country, or first take up some subject that excites us, are longings which no marriage, no travel, no learning, can really satisfy. I am not now speaking of what would be ordinarily called unsuccessful marriages, or holidays, or learned careers. I am speaking of the best possible ones. There was something we grasped at, in that first moment of longing, which just fades away in the reality. I think everyone knows what I mean. The wife may be a good wife, and the hotels and scenery may have been excellent, and chemistry may be a very interesting job: but something has evaded us.
[But] The Christian says, ‘Creatures are not born with desires unless satisfaction for those desires exists’… If I find in myself a desire which no experience in this world can satisfy, the most probable explanation is that I was made for another world. If none of my earthly pleasures satisfy it, that does not prove that the universe is a fraud. Probably earthly pleasures were never meant to satisfy, but only to arouse it, to suggest the real thing. If that is so, I must take care, on the one hand, never to despise, or be unthankful for, these earthly blessings, and on the other, never to mistake them for the something else of which they are only a kind of copy, or echo, or mirage.
— C.S. Lewis, Mere Christianity, 136-137