From Mere Christianity:

God made us: invented us as a man invents an engine. A car is made to run on petrol, and it would not run properly on anything else. Now God designed the human machine to run on himself. He Himself is the fuel our spirits were designed to burn, or the food our spirits were designed to feed on. There is no other. That is why it is just no good asking God to make us happy in our own way . . . God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing.

I was explaining to the dog earlier about the difference between desire and greed. I had graciously offered her some peanut butter as I was making a sandwich, enough that, in my mind at least, a reasonable creature would be satisfied. But not my dog. No, she swallowed it all as fast as peanut butter is willing to be swallowed and came begging again.

Desire is a good thing, a gift from God actually. It plays an invaluable role in our relationship with him, not to mention marriage and other facets of life. Greed is desire that has been hijacked by ego or wounds. It tears away at those parts of life just mentioned by planting in our minds a constant sense of dis-ease, a whisper, that maybe more would be better…”

Desire cries out for ultimate reality. Greed accepts, even promotes, all kinds of lesser substitutes but since they are only penultimate there isn’t any substantive satisfaction. Just more dis-ease, which leads to the overindulgence we normally think of as greed. More and more means less and less, which brings to mind more than a couple things Jesus had to say, doesn’t it?

As C. S. Lewis famously wrote:

“Indeed, if we consider the unblushing promises of reward and the staggering nature of the rewards promised in the Gospels, it would seem that Our Lord finds our desires, not too strong, but too weak.

“We are half-hearted creatures, fooling about with drink and sex and ambition when infinite joy is offered us, like an ignorant child who wants to go on making mud pies in a slum because he cannot imagine what is meant by the offer of a holiday at the sea. We are far too easily pleased.”