The conventional thinking in political circles is that the financial crisis on Wall Street — and, for that matter, Main Street — settles the debate over whether Americans should be able to invest a portion of their contributions to Social Security in private savings accounts.

The argument goes: Imagine what would have happened, over the last week, to the retirement security of millions of Americans if their investment in Social Security had been parked in the stock market.

Fair enough. Investment is always a risk, and many Americans don't like the idea of risking any part of their Social Security. That is true in the best of markets, let alone in one as shaky as this one.

But there is another side to that coin. It could also be argued that our Wall Street woes are an economic wake-up call for Americans, one that reminds them they can't afford to put out of their minds difficult questions about their own financial security just because those questions make them uncomfortable. It makes clear that our elected officials have to show some leadership with tough issues, and not simply kick the can down the road for future generations to solve. And it makes the case that Americans shouldn't put all their retirement eggs in one basket, but should diversify investments and do what they can to preserve Social Security.

We would love to have that conversation. But frankly, we usually wind up having it alone. Neither Republicans nor Democrats have ever shown much appetite for it. So wedded are they to the powerful yet provincial AARP that they're terrified of tinkering in any way with the current system.

The problem is that the system is unsustainable, as should be evident with the impending retirement of 70 million baby boomers - brought to you by smaller corps of younger workers who will be taxed to the gills to pay for it. Consider this: In 1946, the cost of supporting one retiree was divided between 42 workers. Now we're approaching the point where the cost of each retiree will be divided between only two workers. That is bound to put enormous strain on those workers. The real trouble begins in 2016 when - according to the experts - more will be going out in benefits than coming in as payroll taxes.

The financial crisis has changed Wall Street and our lending institutions. But it can't change demographic reality.

Social Security is basically a Ponzi scheme that collects and redistributes wealth from one generation to another. Whether or not we think that is a good and fair idea, that is the system we have.

The question is whether the time has come to alter the formula. Perhaps we could raise the retirement age to 70, or cut benefits by tying them to inflation instead of wages, or means-test the program so that millionaires forfeit their return. Or perhaps, dare we say, we could allow for the private investment of a portion of our contribution to Social Security to try to enhance the return to individuals.

Don't like that idea? Fine. Think it impractical and dangerous? Got it. Let's hear your alternative. Criticizing an idea without proposing a better one is no longer acceptable — not with the wolves at the door.

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