We’ve come a long way in economic thought since Nixon blithely ushered in the era of stagflation with the words, “We are all Keynesians now.”

But the temptation of Keynesianism’s siren appeal — that it is possible for the government to steer the economy with the levers of taxation and spending as precisely as a captain steers a boat through a canal — still lingers on with the intractability of a clingy ex-girlfriend.

It looks as though both political parties have had a pint from the Keynesian Kool-Aid, enthusiastically plugging their bipartisan “stimulus package” as a way to fix the economy by increasing consumer demand.

This sounds like a win-win solution, and in a broad sense it may very well be. But when the rebate checks start going out this week, they probably won’t do much of anything to achieve their stated goal of propping up consumer spending when viewed in proportion to the amount of money given out.

In the government’s view, your ideal reaction to suddenly having a few hundred extra dollars to spend would be to go down to the Apple store in the U-Village and buy a shiny new iPod.

Unfortunately, odds are that you’re probably more worried about tuition bills, student loans and rent than updating your gadget collection.

The “extra money” freed up by the rebate may not be realized until we find that we don’t have to write that last debt repayment sometime in our late twenties, or that we didn’t accrue as many finance charges on our credit cards. We’ll be happy then, but that wasn’t the point of the stimulus program.

Money sent to people in the workforce won’t do much to affect consumer spending either. Barring a massive windfall, such as a lottery win or an inheritance, most people spend according to their income rather than how much money is sitting in their bank account at any given moment. The government’s stimulus transfer will simply be subsumed into efforts to pay off mortgages credit card debt and money for retirement or education. Again, this is great, but it won’t “fix” the economy.

Of course, there’s a strong case to be made that any choice by the federal government to put back in your pocket a portion of what it took out in the first place is a step in the right direction. Trying to force all government agencies to clean up wasteful spending is a noble enterprise. And while a marginal-rate tax cut would be better than a one-time injection of cash, the stimulus package at least does move money from public hands back into private hands in a passable manner.

The only flaw in this abstract justification is the fact that a significant chunk of the money will go to people who paid no federal income tax anyway, making the “rebate” more of an unwarranted handout in some cases. And of course, low-income Americans are the ones who would want to spend the least.

In the end, the economy runs on its own cycle, in a manner too multifaceted and complex for Congress to “fix.” When the economy recovers, it will have been a result of market forces, not a one-time payment.

So when the figurative tax man comes by to return your money, go forth and be happy — but don’t expect your post-graduation job prospects to change for the better or worse because of it.