On a recent trip to Home Depot, our 4-year-old Isaac asked his mother, “Why are we in here?”

“There’s a few things we need,” said my wife.

“Is it something we need, Mommy, or something you want?”

The great danger of teaching your children is that they might begin to listen. Reading Ron Sider’s review of Passing the Plate: Why American Christians Don’t Give Away More Money left me thinking about how much easier it is to ignore teaching when we are adults, and how easily wants become needs. The trends revealed by the book’s data on tithing are not new, but they are startling: A fifth of American Christians give nothing, and the average is 2.9 percent of income. Twelve percent of Protestants give a full tithe, and 4 percent of Catholics do the same. The authors estimate that if only the most strongly self-professing and church-attending Christians were to fully tithe, an additional $46 billion per year would be available for Christian causes.

Forty-six billion is chump change when you are a U.S. automaker looking for a government handout, but it’s serious money to struggling domestic and international Christian parachurch operations. We could do more, we future citizens of heaven, were we to give more from our earthly storehouses.

My experience is that the conversation tends to go in a couple of directions from here. The first is to run roundabout in a big circle, as follows: The data is flawed. Plenty of people call themselves Christian, but they don’t behave like Christians. That, of course, is precisely the point. Although this bit of circle-running allows objectors to salvage their image of the Church, it has the feel of someone cutting off rotten limb by rotten limb, disclaiming his or her membership in His body, and all the while declaring himself healthy.

The second argument is to seize on how much worse those other people are. Catholics give less than Protestants. Democrats give less than Republicans. Atheists give less than Christians. One-legged redheads give less than bug-eyed Virginians. It’s no more fruitful a discussion because that $46 billion foregone every year looms there like a corpse.

Which brings me to what I think we ought to consider, each of us, which is how our mental accounting works to distinguish needs from wants. I think, for example, that I visited Starbucks at least 100 times this year. I am pretty sure—though not completely certain—that I could forgo Starbucks without in fact murdering anyone. I think. Pushing further, it wouldn’t kill my family to forgo meat once a week. And what is a trip to McDonald’s compared to helping fund a missionary? All of us make these small decisions every day—precisely because they are small, because in the moment that five or 10 dollars seems so inconsequential.

Yet even if we were to get our accounting right, and start giving considerably more of our income, there is still this nagging sense that distinguishing needs from wants gets things all wrong. After all, Christ didn’t say for us to set aside everything we want, except insofar as it impinges on the basic necessities of life, and follow Him. He said to take up our crosses and follow Him.

This is the great and final need of man, and his greatest desire as well, converging on one point. It is the imperative that carries him unto death, following the God-man who said, strangely and clearly, come die with me that you might live. Compared to that, parsing needs from wants seems small-minded. And scarcely being able to hand over a nickel from every dollar we earn, in this the richest, safest, most pleasure-laden country on the planet, seems smaller still. In fact, if more of us were faithfully carrying our crosses—and I am at the top of that particular list of cowards—the less time we’d have to spend all that money that seems to be gone by the time the missionaries and hungry children come calling.