The best way to test economic theory is to go to Wal-Mart. Do people buy more of something when its price drops? Just ask that guy in front of you with a six-pack of toilet plungers in his cart. Will people ever be selfless enough for communism to work? Probably not so long as they’re capable of trampling someone to death in their quest for a cheaper pair of underwear.

It’s in Wal-Mart as well where I finally got George Gilder’s point. Gilder was perhaps the most famous proponent of supply-side economics, a catchall phrase that came to mean all that liberals perceived to be evil about the Reagan years, and likewise all that Wall Street bankers and other market-minded folks loved about that era. Gilder argued that the demand side doesn’t drive markets, because the innovations that fuel an economy are rarely foreseen, let alone widely demanded. Instead, innovation—and hence economic growth—is driven by the supply side, by entrepreneurs offering new products and services that people didn’t realize they wanted until they saw it. The path to economic strength, then, is in crafting policies that reward, rather than punish, entrepreneurs who develop profitable innovations.

This came home to me as I stood in Wal-Mart this weekend holding a measuring cup. We already have a measuring cup, but it’s a two-cupper, and sometimes I just need the one cup. And sometimes I need measures of different liquids, which means I have to add something from the two-cupper, and then go fill it with the other ingredient, and then add that one. It seems so much more Food Channelly to have all my ingredients at the ready, each in its allotted cup.

This is no proof of supply-side economics; in fact, it may well be the opposite. But what made me pause was a nearby baking tray, the kind that has some kind of fancy air-cooling layer, or some such thing, that is supposed to make your cookies all the fluffier. I didn’t know they had something like that. And I wanted it, too. Even better, on the aisle I’d just left was one of those hand-held mixers, the kind you put into whatever bowl or cup you’re mixing. At a reasonable price, I should add.

That’s when it hit me, that Gilder was right. I didn’t ask for any of these things, but now that someone had supplied them, I was sorely tempted to load up my cart. Then it also hit me that, though he wasn’t making a theological argument, Gilder had touched on something spiritual, which is that our darkened hearts are capable of bottomless hunger. If someone places something attractive before us, even though we were content before, the very existence of it will open up a hole, a want, a craving. And the worst thing we can do is give in to the craving, because we’ll only train ourselves to want more and more.

I’ve never been much of an ascetic—I would fast in a dire emergency, or keep an involuntary vigil when compounded worries kept me from sleep—but I’m starting to see the value of denying our wants. I’m not talking about moderation, about denying ourselves things we don’t really need, whatever that means. I’m talking about denying ourselves things we might actually have a good use for, solely for the sake of keeping our flesh in check.

It’s easy to say right after Thanksgiving, of course, but I’m planning on doing a good bit more fasting in the coming year, and less purchasing as well, and not just because the economy is going into the tank. It’s the spiritual strength of this country—and of me—that’s in even greater danger of going into the tank, and all these fat and easy years have made us none the stronger. So my first victory was putting that measuring cup back. It’s just one cup, but I suppose that’s how a lot of big things get accomplished, a few ounces at a time.