Call it the paradox of being old and thinking young. A man in his 90s makes the case for the future -- even the future in space -- as well as anyone. The man is Jacques Barzun, the eminent Columbia University historian, and his argument is presented in From Dawn to Decadence.

At 877 pages, it’s a brick. And the subject -- the last 500 years of Western Civilization -- is even heavier. Yet it’s been on The New York Times best-seller list for the past six weeks, reaching as high as #3.

At a time of worldwide economic boom, it’s easy to criticize Barzun’s thesis. America, in particular, seems full of confidence and swagger at the dawn of the 21st century.

And yet as anybody clicking on to SPACE.com is painfully aware, one of the characteristics of Western Civilization since the late 15th century -- an enduring commitment to exploration -- is strangely absent from today’s world. Humans have not been to another world since the Apollo 17 astronauts, Eugene Cernan and Harrison Schmitt, last lifted off the moon in December, 1972.

One of the burdens hindering space exploration is its terminology, which has naturally, but unhappily, been adapted from colonialism and imperialism. So along with images of astronauts and rocket ships come visions of conquest and colonization -- and from there, it’s just a hop and a skip to thoughts of "manifest destiny" and "white man’s burden."

Perhaps conscious of this unfortunate linguistic similarity, the late Gerard O’Neill, the Princeton physicist, often spoke of the "humanization" of space. Yet even he couldn’t completely avoid the word-choice-trap; the full title of his 1977 book, laying out his theories of orbiting "islands in space," is The High Frontier: Human Colonies in Space.

Barzun can’t help the pro-space crowd with prospective advice on future nomenclature, but he can help the outward-bound with perspective on the past.

Consider, for example, Christopher Columbus, the DWEM -- dead white European male -- who helps kick off Barzun’s narrative. Ignoring the pieties of political correctness, which he seems to regard as little more than a passing fever, Barzun labels Columbus a "true hero."

Recalling the worldwide outcry against the Genoese seafarer during the quincentennial of his voyage in 1992, Barzun fully acknowledges the atrocities against Native Americans committed by the Spanish and those that followed the conquistadors. "But to blame Columbus" for all this, Barzun insists, "is a piece of retrospective lynching."

Indeed, Barzun views the centuries-long flow of Europeans across the Atlantic and other oceans as inevitable; he has a lofty sense of historical tides that begs comparison to Edward Gibbon, Arnold Toynbee -- or Isaac Asimov. And so, just as "revisionist" and "post-revisionist" historians have endlessly spun the wheel of historical evaluation on figures ranging from George Washington to Richard Nixon, it’s possible to imagine that Barzun and those that come

after him will help improve Columbus’ current low standing.

And if past explorers get a boost, then maybe future explorers will, too.

Barzun makes empathetic room for other explorers and adventurers, real and imagined, from Henry David Thoreau to John Muir to Robinson Crusoe. He even pauses to praise the father of science fiction, Jules Verne, for his "stirring tales" about "going to the moon, traveling under the sea, and using power at a distance by means of rays."

Yet when he comes to the present, Barzun suggests that underneath the hum and thrum of the cyberized, globalized economy, a once-pulsing ventricle of the human heart -- the desire to strive, to seek, to find, and not to yield, as Tennyson put it in his poem "Ulysses" -- has suffered an infarction.

We have tumbled into a time of decadence, the nonagenarian argues, although he looks to a better future he is unlikely to live to see. Remarkably for a liberal-arts Ivy Leaguer, he is unabashedly pro-science and pro-technology, citing "the wonders of the space program."

Barzun closes his book with a prologue for the future, in which he extrapolates current trends leading to "a blight . . . of boredom."

What cures that? "A resurrected enthusiasm in the young and talented," he suggests, "who keep exclaiming what a joy it is to be alive." It is from them that a "renascent culture" comes.

The cultural and political crusade for space exploration, of course, is in desperate need of a renaissance. So if the would-be colonizers --oops, make that humanizers -- of space can arm themselves with Barzun’s historical perspective, they could begin a new chapter in the course of

human events: a progressively pro-space narrative.

With the right leadership, they could be persuaded to pick up where Columbus, Verne, and Cernan & Schmitt left off, and so begin the new millennium with a new dawn of exploration and expansion.