Most historians agree that earthquakes, droughts or barbarians did not unravel classical Athens or imperial Rome.
More likely the social contract between the elite and the more ordinary citizens finally began breaking apart - and with it the trust necessary for a society's collective investment and the payment of taxes. Then civilization itself begins to unwind.
Something like that has been occurring lately because of the actions on Wall Street and in Washington, D.C. The former "masters of the universe" who ran Wall Street took enormous risks to get multimillion-dollar bonuses, even as they piled up billions in debt for their soon-to-be-bankrupt companies.
Financial wizards like Robert Rubin at Citicorp, Richard Fuld at Lehman Brothers and Franklin Raines at Fannie Mae - all of whom made millions as they left behind imploding corporations - had degrees from America's top universities. They had sophisticated understanding of hedge funds, derivatives and subprime mortgages - everything, it seems, but moral responsibility for the investments of millions of their ordinary clients.
The result of such speculation by thousands of Wall Street gamblers was that millions of Americans who played by the rules, and put money each month away in their 401(k) plans and elsewhere, lost much of their retirement savings. Many likely will have to keep working well into their 60s or 70s, and delay passing on their jobs to a new generation awaiting employment.
Yet most disgraced Wall Street elites will retain their mega-bonuses and will not go to jail. Their legacy is having destroyed the financial confidence of a society that depends on putting capital safely away to be directed for investment by responsible overseers.
A sort of unraveling of the entire system of credit and debt may follow from the loss of confidence in Wall Street. Ads on radio now blare out to the rest of us how to renegotiate our mortgages, how to avoid paying the Internal Revenue Service and how to walk away from freely incurred credit-card debt. We hear not to trust in mutual funds or even banks - but instead, like medieval hoarders, to revert to the age-old safety of gold. Apparently, the institutions run by our elites aren't trustworthy, so why should we put any faith in them?
Meanwhile, we are learning that the brightest and best-educated Americans at the highest levels of government simply refuse to pay their required taxes. Yet because the IRS audits a tiny percentage of taxpayers, voluntarily compliance with our tax code is the glue that holds together a sophisticated society and separates it from a failed state.
Rep. Charles Rangel, New York Democrat, is the chairman of the Ways and Means Committee that overseas our tax laws. But his lawyer recently admitted Mr. Rangel didn't report some $75,000 in income.
Timothy Geithner is the new treasury secretary and oversees the IRS. Yet Mr. Geithner improperly wrote off his son's summer camp fees as a dependent-care expense, and failed to pay thousands of dollars in Social Security and Medicare taxes.
Then there is former Sen. Tom Daschle, who was nominated to be secretary of health and human services. It was revealed that he owed the IRS more than $140,000 in taxes on unreported free limo services; as a result, he had to ask President Obama to withdraw his nomination.
Nancy Killefer, who just withdrew her name from consideration as "performance czar," did not pay required taxes for domestic help.
The husband of labor secretary nominee, Hilda Solis, had more than a dozen liens for back taxes on his property and just now paid up amid public outcry. (The issue is relevant, since the couple filed a joint income tax return.)
Mr. Daschle, Mr. Geithner, Mrs. Killefer and Mrs. Solis did not disclose their tax liabilities until they were nominated to high office and scrutinized by the press.
And they apparently did not pay their back taxes until their appointments were in jeopardy from public disclosures. That raises disturbing questions: Would we have known about such tax dodging had our best and brightest not wished career advancement in government? And would they have ever paid up if they had not been caught?
Take your pick - on the one side, we have free-market capitalists who took huge amounts of money as their companies eroded the savings of tens of millions; on the other, we have supposedly egalitarian liberals who skipped paying taxes. The result is the same. Our best educated, wealthiest and most connected in matters of finance proved our dumbest - and our political leaders were less than ethical in meeting their moral responsibilities as citizens.
If ordinary Americans were to follow the examples of Wall Street and Washington elites, the nation would neither collect needed revenue nor invest its capital. All that is a recipe for national decline and fall.
Victor Davis Hanson is a nationally syndicated columnist, a senior fellow at Stanford University's Hoover Institution and a recipient of the 2007 National Humanities Medal.