Thanks to Barack Obama's Wednesday speech at West Point, everyone now knows that "America has rarely been stronger relative to the rest of the world," and that those who "argue otherwise — who suggest that America is in decline, or has seen its global leadership slip away — are either misreading history or engaged in partisan politics."

I sure am glad he clarified that.

There's just one problem: the U.S. most certainly is in decline relative to other nations.

I understand perfectly well why the president feels he cannot admit this (for political reasons), but it's unfortunate that he also feels the need to dismiss those making the opposite claim, and not only because they're right. It's unfortunate, above all, because the dismissal leaves untouched a pair of assumptions that the president's growing chorus of neoconservative and liberal internationalist critics nearly always make about America's relative decline — namely, that it can be stopped, and that it should be stopped.

Neither assumption is correct.

The most thoughtful form of the neoconservative/internationalist critique of President Obama's foreign policy can be found in the current issue of The New Republic, in a lengthy essay by Robert Kagan titled "The Allure of Normalcy. (If reporting in The New York Times is to be believed, Obama's speech was written in part as a rebuttal to Kagan.)

Kagan's guiding assumption throughout the essay is nicely encapsulated by the title of a grouchier and less sophisticated but otherwise quite complimentary 2009 essay by Charles Krauthammer in The Weekly Standard: "Decline Is a Choice."

Actually, it isn't.

America's decline relative to other world powers is very real, but it's happening apart from anything Barack Obama has done, and there's very little he or anyone else can do to stop it.

As my friend Noah Millman noted in a cogently argued blog post a few weeks ago, once an entity — a business, a nation — achieves a certain level of prominence, it has nowhere to go but down relative to competitors. This happened to Microsoft when it dominated 90 percent of the market for computer operating systems. And now it's happening to the United States, which came out on top after World War II and kept right on expanding its predominance through to the end of the Cold War, when, for a brief time, America was the overwhelmingly dominant power on the planet.

For a moment, it really was a unipolar world.

In absolute terms, the U.S. will remain the biggest single military power for some time to come, but other powers are rising, foremost among them China. When it comes economic heft — which can and often does fuel a nation's long-term military plans and ambitions — our dominance is far more precarious, with China already poised to surpass us by some measures before the end of this year, and several other nations and regions growing at rates that could have them overtaking us before the end of the century.

It's only an anecdote, but I think it's a telling one: Back in 1996, I won a grant from Germany's Alexander von Humboldt Foundation that enabled me to spend a year in Berlin conducting research on my doctorate. The grant — the German Chancellor Fellowship — had been founded by Helmut Kohl in 1990 to ensure that close German-American ties would persist after the fall of the Berlin Wall, the reunification of Germany, and the end of the Cold War. For that reason, the fellowship was available only to Americans.

Yet just a few years after my return from Germany, the applicant pool was expanded to include members of the Russian federation. Then it was enlarged again to permit Chinese applicants. Most recently, the foundation began accepting applications from India and Brazil. In 24 years, the U.S. has been demoted from a singular nation to one of five.

Welcome to the multipolar world.

Neocons and liberal internationalists can rail against this development all they want, but none of them has a plausible prescription for halting it — because there isn't one, at least short of actively seeking to impede the economic growth and expanding military capacity of other nations and regions of the world. That would merely gain us new and increasingly powerful enemies, and (paradoxically) make us look unworthy of acting as the leader of a genuinely free world.

Decline is not a choice. It's a fact. One we need to get used to.

But this doesn't mean the proper response is despair.

That's what one might conclude from reading Kagan's essay, which derives much of its cogency from its portrayal of the era stretching from the end of World War II to 2008 as some kind of respite from the bloody savagery of human history — savagery to which the world will rapidly return if the U.S. continues on its perilous course of choosing decline.

Unlike some cruder critics, Kagan doesn't explicitly state that an absence of active American military domination will set up the world for an instantaneous replay of the catastrophic 1930s. But an ominous implication nevertheless permeates his essay: by not bombing Syria and not doing some unspecified thing to get Vladimir Putin to pull back from Crimea, we run the risk of returning to the house of horrors that was international affairs until the U.S. finally took charge and instilled some order beginning in 1945.

To call this account a distortion of the facts would be an understatement. Leave aside the superpower nuclear brinksmanship that for decades during the Cold War threatened to annihilate the human race. What about 1.2 million deaths in the Korean War (1950-1953)? And 2.1 million deaths in the Vietnam War (1955-1975)? And nearly half a million deaths in the Iraq War? What about U.S. meddling in Iran in 1953? And in Chile in 1973? And in Nicaragua in the 1980s? And in the Iran-Iraq War during the same period?

The point isn't that all of these and many similar interventions over the past seven decades were unjustified. (I think many of them were foolish, but that's an argument for another day.) The point is that the decades following the end of World War II were not some global holiday from history made possible by the warm and fuzzy hegemony of the United States. Some American policies during the Cold War had very good effects. But others had very bad effects, the consequences of which we're still contending with today.

There was war and suffering before and after 1945, before and after 1989, before and after 2008.

The same will be true tomorrow, and tomorrow, and tomorrow. Muddling through is the way of the world. The best we can hope for is to muddle through with our eyes wide open. And today, clear-sighted clarity demands that the president, no less than his smartest critics, grapple honestly and forthrightly with the distinctive dangers and opportunities afforded by America's inexorable decline.