The 300 millionth American was born (or naturalized) last month, and the usual suspects marked the occasion with the usual hand-wringing about America's allegedly heavy "ecological footprint;" somewhere, I'm sure, Paul Ehrlich was bemoaning profligate population increases and predicting environmental and economic catastrophe just around the corner - as Dr. Ehrlich has been predicting, with dogged regularity, for almost four decades. I suggest that the 300 millionth American is cause for celebration. It's also a cause for reflection.

Celebration, because the United States is the only advanced industrial country with a growing population. India may eventually prove the other exception to the rule, but at the moment, we're it: everyone else in the global major leagues is depopulating, in some instances drastically.

Demographers now estimate that, when the 400 millionth American becomes a citizen of the Great Republic c. 2050, 60 percent of Italians won't know, from personal experience, what a brother, sister, aunt, uncle, or cousin is; the Wall Street Journal recently reported a survey indicating that half of Italian women age 16-24 want no children. Other European states --- Germany, Greece, and Spain prominent among them --- are on the precipice of the demographic death-spiral, thanks to lower-than-low birth rates.

This will lead, in the short term, to fiscal disaster (not enough taxpayers to fund all those guaranteed and government-sponsored European health care and pension schemes). In the long run, it may lead to the Islamification of significant parts of Europe, not by conquest but by default ("Mohammad" is already the most popular name for newborn boys in Belgium and Holland, and it's among the name-game leaders in Great Britain).

As I argued in "The Cube and the Cathedral," this extraordinary depopulation is one expression of a crisis of civilizational morale --- which in turn is one by-product of European high culture's rejection of the God of the Bible. Seems that, when you cease to believe in a world beyond this one, you can't be bothered with repopulating the world you live in. So if America is hanging in there with a replacement-level birthrate, that suggests that we're not, as a country, stuck in the European slough of despond (even if parts of blue America are).

That American birth rates are higher among recent immigrants suggests the challenge implicit in population growth: the challenge of assimilating and acculturating large numbers of new citizens, many of whom come from different cultural and linguistic orbits. The United States has traditionally done a good, if occasionally rough-edged, job of this. Continuing to do so requires us to strengthen civic education: the U.S. is a proposition country, and unless new Americans (and the children of long-time Americans) learn the "proposition" --- and learn how to defend it, intellectually --- fault lines will appear in our society, and we'll forget what it is we're defending.

Once again, look at the canary in the mine shaft, a.k.a., Europe. Europe's failures to foster a respect for western democratic values in its late-20th century immigrants are a principal reason why numerous parts of the continent are 21st century beachheads of the Arab-Islamic world where the writ of British, French, Dutch or Belgian law does not run.

Then there is the question of language. Bilingualism is not, historically, a prescription for national solidarity: witness Canada or Belgium. English-language competence is, and will remain, the entry ticket to economic success in America (some would argue that minimal English competence --- can you read a ballot? --- should be a pre-requisite for participating in the political community by exercising the franchise, but that's another argument for another day).

I'm quite comfortable with certain bishops' insistence that their new priests learn Spanish. But as I told one bishop as he headed off recently for an immersion-Spanish program, "The first thing you have to learn to say in impeccable Spanish is 'Learn English!'."

Notwithstanding the problems to be sorted out, the more important point is that America has retained the cultural and moral vitality to create the human future in the most elemental sense, by creating successor generations. Thus, a hearty welcome to Mr. or Ms. 300 Million. We're glad you're here.

George Weigel is a senior fellow of the Ethics and Public Policy Center in Washington, D.C.