Comparisons between the Roman Empire and America are commonplace but also of enduring interest to pessimists seeking the secrets of decline. One explanation for Rome’s fall is that it was overrun by barbarians. But barbarians were already on the inside, many of them fighting for the emperor, as historian Finley Hooper observed. Incessant warfare and plagues were factors. A shortage of manpower and depletion of the soil may have contributed to economic decline.

The theory that seems most relevant to contemporary America is simple: The Roman Empire went bankrupt. Taxes soared even as the economy withered. People entered the civil service, where they could join the “tax-collecting units” oppressing those who still worked. Moreover, Rome became infected with a “loss of spirit,” wrote Hooper. Fear about the future pervaded the whole society. People felt that they had no say in their own destiny. The individual’s sense of responsibility “had been drained away by the increasing use of coercion by the government even for what seemed desirable goals at the time.”

All those notes have a familiar ring today. We may not feed people to lions, but our governments are very good at dreaming up “desirable goals” — regulatory fine-tuning of the cosmos, attempts to remove anxieties and discomforts from life. As with the Romans, the goals have outrun our means to pay for them. Increased longevity and technological advances have confounded the assumptions on which our entitlements were originally based. The money to pay for 30-year retirements and limitless health care simply isn’t there.

In short, our expectations have to change. Our joyride on high octane consumption and corrosive debt is coming to an end. We don’t need visionaries who promise to “change the world.” We need sober bean counters. We must live within our means. Politicians won’t save us. They’ll continue to promise free lunches while they demonize one another, as if the solution to our problems lay in a simple choice between Democrats and Republicans. Meanwhile, they’ll keep picking our pockets and distributing the proceeds to special interests.

Standard and Poor’s recently downgraded the credit of the United States. Several states are headed towards bankruptcy. The rest of the world is gaining on us, but we still act as if we’re the only game in town. We beat our chests about “American exceptionalism” while China eats our lunch.

Can we summon the same kind of energy and determination to face this challenge as we have in times of war? Or are we “exhausted” as the Romans were and so addicted to our entitlements that we’re incapable of reform? The image comes to mind of the Romans huddling inside their walls, while the conquering warlord stood at their gates, laughed at them and declared, “The thicker the hay, the easier it is mowed.”