1. We'll conserve more. This is a no-brainer to figure out. When energy costs more, we figure out ways to use less of it. That's good. If demand goes down, the price might also.

2. It replaces the $1 gas tax Congress never passed (and never will). Virtually every economist of every stripe says America would be stronger if we had long ago raised the tax on gasoline by $1 a gallon (or bring it up to $1 a gallon). Right now the federal tax is 18.4 cents a gallon and combined federal and state taxes are about 50 cents a gallon. Had Congress turned $2.50 a gallon gasoline a couple years back into $3.50 a gallon gasoline, maybe we'd be further down the conservation path in 2008. Why didn't this happen? Even someone as dim-witted as a Congressman knows, instinctively, that way a rat knows to avoid burning buildings, that a dollar-a-gallon gasoline tax is political suicide. It's a balancing act: America's future vs. the Congresman's political future. Instead, the rats stick with the tried-and-true forms of suicide, such as hanging out in airport restrooms.

3. $4 gasoline fights global warming. When something costs too much, you use less of it. Use less fuel, generate less CO2, (maybe) save the planet. I'm still not 100% convinced this global warming thing is real, but every month a couple more personal percentage points of personal opinion shifts from undecided to more-likely-real-than-not.

4. Big Oil finds more oil in the U.S.A. In some parts of the world, you can pump oil for a cost well under $10 a barrel, which means a profit of more than $100 a barrel. The more oil sells for, the more Big Oil (our Big Oil) and wildcatters are willing to search out new oil deposits, or tap into known reserves that were too costly to extract when oil was under, say, $50 a barrel. It's possible they'll then reap obscene profits, which means widows and orphans should rush out and buy Exxon stock and live comfortably on the dividends that will allow them to buy $4-a-gallon gasoline.

5. Alternative fuels look better and better. The more traditional motor fuels cost - gasoline and diesel made from dead dinosaurs and other stuff from long ago - the more things such as ethanol and biodiesel look cost-effective. And the more it makes sense to employ start-stop engines, brake regeneration, and full-on hybrids, that add a couple thousand dollars to the price of cars.

So next time you run your 27-gallon SUV's tank down near empty and the fill-up tops $100, just remember there's a bright side to the high cost of gasoline.