Back when I was in school, I performed a scientific experiment in which I poured a liquid of one color into a beaker that contained liquid of a different color. At first the liquid in the beaker was diluted, but as I kept pouring, the poured liquid eventually overtook the liquid in the beaker, creating an entirely new substance.

That’s what is happening in Europe as thousands of migrants flee their home countries, seeking refuge in the European Union. Germany, alone, is expected to have received 800,000 migrants by the end of the year, four times last year’s number.

German Chancellor Angela Merkel has suspended the EU’s Dublin Regulation for Syrian migrants. Under the rule, writes The Telegraph, “…migrants can only apply for asylum in the first EU member state they enter, and face deportation if they try to apply in another. But Germany … has now ordered its officers to process applications from Syrians even if they have made their way through other EU countries.”

Critics of the Dublin Regulation have called it expensive and ineffective. Many Syrian migrants reach Greece first, but decline to seek asylum there, preferring to push on toward Hungary, which is considered the gateway to Europe. Merkel has said she might reinstate border checks, which was a regular practice before the EU was created. She should.

Let’s learn what these migrants and immigrants likely mean by “freedom.” If they mean Sharia law, that is not freedom for Europe, or for America.

That most of these migrants come from Muslim countries raises several important questions. The first is how many actual or potential terrorists are among them? Second, why would Muslims, many of whom believe the West is decadent and anti-God, want to come to Europe? Third, why haven’t these migrants sought refuge in other Muslim countries, which one might think would be their first priority?

No nation, no continent, can survive uncontrolled immigration, especially when it involves people whose language, religion, culture and worldview differ — in some cases radically — from the countries to which they are migrating. Uncontrolled migration in Europe and illegal immigration in the United States spell an eventual death knell for both countries, which is, no doubt, the intent of ISIS, which is reportedly backing this flood of humanity. Will those flooding Europe eventually embrace European values, or when their numbers grow to the point where they form a significant percentage of the population, will the migrants demand that their values and religion dominate?

In the U.S., cries of “racism” in the immigration debate have replaced sound reason. But this isn’t about discriminating against people of a different language or color; it is about preserving what we have, not only for those of us who have contributed to making America what it is, but also for immigrants who would not only like to partake of our success, but contribute to it. If nations want to preserve the lifestyles and culture which they and their forebears have worked and fought to create and sustain for themselves, their posterity and for immigrants, borders must be controlled and assimilation must be a top priority for those who are allowed to enter. Otherwise, nations become disunited with competing subsets jostling for power, influence and benefits.

Those who support “open borders” have an obligation to tell us when enough is enough. Must we wait until the American “liquid,” which contains the values, faith and prosperity from capitalism that built and sustained us through wars and depressions, is replaced by a different “liquid”? What happens when the “takers” outnumber the “makers”? If we wait for that day to arrive before we act, it will be too late.

Yes, give us your tired, your poor, your huddled masses yearning to breathe free — but legally, in an orderly fashion and not en masse. And let’s also learn what these migrants and immigrants likely mean by “freedom.” If they mean Sharia law, that is not freedom for Europe, or for America.

If the EU and the U.S. fail to address this very real crisis, we and they are assisting in national suicide.

Cal Thomas is America's most widely syndicated op-ed columnist. He joined Fox News Channel in 1997 as a political contributor. His latest book is "What Works: Common Sense Solutions for a Stronger America" is available in bookstores now. Readers may email Cal Thomas at tcaeditors@tribune.com.