Everything has changed.

It is impossible now, as the Paris attacks are still fresh, to imagine a Ben Carson in the White House. It is impossible to envision such a man, bereft of foreign policy experience, acting as commander in chief. It is just as impossible to think of Donald Trump in the Oval Office. It is horrifying to imagine him sitting there, thinking of the world as a board game — real estate, of course, maybe Monopoly — convinced that the world will conform to his grandiosity. It is also difficult to see Carly Fiorna there, another one who thinks that ambition is the functional equivalent of experience. Bernie Sanders, too, has had his day. Suddenly, big banks are the least of our problems.

Friday’s attacks changed the world in fundamental ways. The targets struck were, as they say, soft; they were chosen, if not at random, then in some unpredictable fashion. It is hardly possible to protect every restaurant, tavern — even music venue. This was a terrorist attack whose intent it was to terrorize, to fundamentally shake an entire society. It will take some days, but that goal — despite the very good words of political leaders and the marvelous singing of “La Marseillaise” in the soccer stadium — will be realized.

Europe is awash with Muslim migrants. Even before the current crisis, France was about 10 percent Muslim. Already, European countries like Poland are pushing back, clearly saying they have had enough. Central and Southern Europe is in a fence-building frenzy. Germany, the unlikely capital of tolerance, will start to clamp down. Europe has never been particularly good at assimilation. It will start becoming better at ugly repression.

It is one thing to tell a people that large-scale immigration will cost them some money. It is quite another to say it will make you less safe. That, of course, will be the message, and it will resonate. After all, one of the terrorists was identified as a Syrian, who had come to France as a refugee. A government that cannot make its people feel secure is a government that itself is not secure. It will not endure. In the carnage of the Paris attacks is the stuff of demagoguery. Europe will veer to the right — maybe extremely so.

In America, the isolationists — Sens. Ted Cruz (R-Tex.) and Rand Paul (R-Ky.), etc. — will point out that the Paris attacks might be payback for Paris’s attacks on the Islamic State. Possibly. This, too, might resonate, but we were attacked 15 years ago for no apparent reason and we might be attacked again. We might not consider the Islamic State our enemy, but not only is there is no reciprocity here, but it is the enemy of all we stand for. The world has grown too small and dangerous for isolationists. It is too complex for the vainglorious amateur. Bad days are coming.

In a prescient column for London’s Sunday Times, former assistant secretary of state James Rubin on November 8 virtually predicted the Paris attack: “Think about it. Imagine if (the Islamic State’s ) leaders decide it’s time for payback for all those dozens of countries in the international coalition attacking Isis from the air. Then imagine the same people who were capable of burning a Jordanian pilot alive, beheading journalists and raping young girls being let loose on the streets of London, Berlin, New York, Paris and Los Angeles.” As far as Paris is concerned, we no longer have to imagine.

The situation in the Middle East cannot be ignored. Just as the United States once could not countenance a fascistic Europe so it cannot now countenance a fascistic Middle East. This is not a clash of religions; it is a clash of ideologies. The dead and wounded of Paris were not shot because they were Christians or, possibly, some Muslims and Jews as well, but because they were French.