I came across this sign in Salzburg yesterday. The top part, in big letters, is very clear. And the asterisks are a courtesy. The bottom part, in little letters, means “Music has no borders.”

So true. Music has no borders. In Mozart Square, here in Salzburg, they are having what they call “Open Piano.” A piano sits in the middle of the square, for anyone to play, during certain hours. A few days ago, a young Chinese woman played a Scriabin sonata.

A young Chinese woman, an old Russian piano sonata, an even older Austrian city — Mozart’s hometown. Do you call that “globalism”? “Cosmopolitanism”? Some other bad word? Whatever it is, it’s wonderful, and long may it wave.

If music doesn’t have borders, countries certainly do, and must. National sovereignty is not a crime, or even an error. It is an ingredient of a just order. What about immigration? The question varies from country to country, but, in general — certainly for the United States — I’m in favor of enlightened restrictionism.

There’s a phrase to tick people off, on all sides. “Who’re you callin’ unenlightened?” Anyway, we can debate, and do. Everyone’s a restrictionist to one degree or another, unless you’re an open-borders person.

So far, it seems, Joe Biden is the only one in the Democratic presidential field to say no to open borders. Would the others sober up, if they had the office? It’s hard to tell.

I know one thing: The “F*** Borders” people are the best friends the hard anti-immigration people ever had. They are a gift from heaven (or somewhere) to them. Twenty years ago, our David Pryce-Jones and others said, “You know, if the mainstream parties don’t address questions of national sovereignty and immigration forthrightly, they will leave the field open to harder men: even to fascists.”

Wise words, which have special resonance on this continent, Europe.