There is a surreal quality to the freshets, streams, rivers, and oceans of words expended on the immigration issue, without a word on the big point.

Senior Fellow Ben Wattenberg

We have heard all about the dueling studies on jobs, welfare, deportation, gangs, culture, guest workers, and terrorism. When as astute an observer of the American scene as Robert Samuelson calls for an obscene and politically catastrophic 30-foot wall along the Mexican border, echoing an earlier position of lock-and-load Pat Buchanan, you know something is awry.

As it happens, I favor President Bush's courageous stand, but even he doesn't mention the big one either.

Namely: American greatness and influence depend on immigration and assimilation. The U.S. is the only major country in the world growing at a moderate but geometric rate, while all the others shrink, including the two great peasant giants, China and India. (If you're an investor, bet on India.) Europe is turning into a theme park with fewer and fewer shows and barkers.

If you know that American greatness, with its concomitant problems, comes from immigration and subsequent assimilation--immediately, or in a generation or two--you understand the situation. If you don't, ask an immigrant cab driver in any big city to explain. Immigration and assimilation are our most important comparative advantages in a roiling world. Does it cause problems? Sure. What in the realm of public policy doesn't? (Always answer a question with a question.)

There's nothing wrong with Mexican immigrants. My favorite stats come from the Defense Department, which has data on most everything except who will win the war. They calculate that Mexican-American GIs have been awarded proportionately more Congressional Medals of Honor than any other sub-group in the American military.

U.N. projections show America growing from 300 million to 400 million to 500 hundred million by 2300, but they underestimate.

America is influential now, albeit unpopular in some, but by no means all, places. The Indians like us, which is nice, because they will likely be our most important ally as the years roll on.

Immigrants are our best publicists. They fly home on cheap flights, they e-mail home, they use their cell phones to say America is O.K., and then some. They send home "remittances" to their families, the best form of foreign aid. Immigrants have an average age of 29. They will pay into Social Security and Medicare for 40 years before getting a nickel back. This, we want to encourage!

At its most elemental, size means it is easier to fund a defense force, which is cheaper per person when paid by 500 million people instead of 300 million. That is a particular advantage when other nations are shrinking--albeit some of them getting richer, like the China. It means more influence available for export. All things being equal, which is often the case, a large population yields power and influence. Belgium won't have either.

Diminishment means "old people, in old houses, with old ideas," as French demographer Alfred Sauvy said in the 1930s. It also means empty houses with falling prices, a shrinking market, and a shrinking labor force.

But it is much more than that. Americans are the principal purveyors of liberty and democracy to the world--no small matter. We have not done it perfectly, but we have done more than any nation in history has. It is likely what we will be remembered for. As John McCain says, we need a cause larger than ourselves. That's mine.

The more of us there are--mixing, matching, blending--the easier the task becomes. That can yield greatness and sadness. Most Jews want their children to marry other Jews, but half of them don't. Israel Zangwill was right; we are a melting pot--although Pat Moynihan used to point out with glee that Zangwill later emigrated to Palestine!

I have testified to Congress on this issue several times. They invariably ask about the same tired old things: jobs, welfare, deportation, culture, gangs, guest workers, terrorism, and so on. (Mexicans aren't terrorist threats.) On immigration matters, the members of Congress don't give much thought to macro-America and global influence.

Native Americans, slaves in chains, George Washington, Albert Einstein, and the guys who started Google came from somewhere else. With earlier restrictions we could have become Australia or Canada. (Canadians let in a lot of immigrants in a wiser manner than we do, and then many of them promptly come here, including a few terrorists.)

In any event, it's a dumb show. A nation that can't keep out illegal drugs, can't keep out illegal immigrants. If we try to do it harshly, we are begging for trouble with Mexico, and with observers around the world. President Bush is on the right track; the road to citizenship should be open, albeit with penalties to make up for prior illegality.

Are we are going to be the great country in the world, or not? I vote yea.

Ben J. Wattenberg is a senior fellow at AEI.