Dear Louisa, Doug, Jimmy and Katie:

Under the Christmas tree this year were two “memory books” to be filled out by your grandparents. The gifts were a bit disconcerting: a reminder that Nana and Papa won’t be around forever. But they were also flattering: Who among us does not want to think their memories will be treasured by future generations?

The books are mostly concerned with the sort of detail (“The first car I drove was ___,” “I once got into hot water for ___”) that will make for fun comparisons in the future. But when you come of age, here is what we would really like you to know: just how lucky we are to be Americans.

As 2005 passes into 2006, you might be tempted to think otherwise. We are bombarded with images of war abroad, moral decay within and signs of a collapse of economic discipline. The “American era,” we are told, may be passing. As historian Victor Davis Hanson makes clear in his fine new book, “A War Like No Other: How the Athenians and Spartans Fought the Peloponnesian War,” which chronicles the decline and fall of democratic Athens, it has happened before.

Nobody could imagine that mighty Athens could lose. But three decades of fitful but murderous warfare against the expanding empire of Athens by Sparta and its neighbors, combined with imprudent Athenian leadership and some bad luck (in the form of a devastating plague that killed off a quarter to a third of the population of Athens), brought the capitulation of Athens in 404 B.C.

The great historian Thucydides, who nearly died of the plague and wartime rigors himself, observed how Athens also collapsed from within: “[C]itizens felt it better to spend quickly and live for pleasure, deeming both their bodies and their possessions as things of a day. Careful adherence to what was known as honor was popular with no one, inasmuch as it was doubtful whether anyone would be spared to attain it…. Reverence of the gods or respect for man’s law there was neither to restrain anyone.”

Does such a fate some day await America? Perhaps. But your grandmother and I were born in the early days of World War II, when half the world had been overrun by barbarians and America was still suffering the ravages of Depression. We also lived through the agony of Vietnam, where the death toll was far higher than Iraq. And then there was the Great Inflation of the 1970s, which in many ways was more subtly destructive of the economic and social fabric than the great deflation of the 1930s.

Each time America bounced back. And for that we largely have our Founders to thank. They constructed a durable system that allows for energetic government in time of true crisis but provides checks and balances that tend to restrain leaders from pursuing grand illusions of the sort that led to the downfall of Athens, where democracy was of a very limited sort.

American involvement in Iraq may prove to be imprudent. But if it does, our political system will move to correct the error. It’s significant that when the Framers met behind closed doors in Philadelphia in 1789, they understood their aim to be the creation not of a perfect union but “a more perfect union,” in the words of the Constitution.

They succeeded. There may be no permanent victories in our system of compromises, but that also means there are no permanent defeats. Which is why, when you are old enough to read this, and with a little effort on your generation’s part, you too will count your blessings on living in what will still be the greatest country on earth.

Love, Nana and Papa.

Mr. Bray is a Detroit News columnist.