Donald Trump gave a speech this week urging the equivalent of an ideological litmus test as a prerequisite for Muslims to enter the United States under our immigration laws. Whether or not to administer some kind of test to Muslims, or to require an affirmation from a Muslim that he or she subscribes to constitutional values, shocks many Americans, because we don't like the idea of singling people out based on race, religion, or the like.

But is there a rational basis for it? Trump's remarks got me thinking once again about assimilation, and often the lack of it, where immigration is concerned, because at heart that is what is at stake. We have seen the consequences of restive populations of unassimilated Muslims again and again in recent months throughout the United States, Europe, and elsewhere, as radical Islamists attack innocents in trains, churches, public squares, restaurants, nightclubs, and boulevards.

Assimilation, this notion that America should be a "melting pot", appears in many circles to be passé, having given way to the much more fashionable "salad bowl" school of thought instead, because it accords better with the modern creed of multi-culturalism held dear among many (but not all) liberal and progressive thinkers.

When Trump raises the sensitive issue of Muslim immigration, it makes many people uncomfortable, because in our society, people's beliefs are not put on display. But this is not true in many other societies that don't share our western Greco-Roman / Judeo-Christian underpinnings. In fact, quite the reverse is true in the more strict and fundamental Islamic regions, because followers of the prophet Muhammad who most closely and rigorously adhere to Islamic law (sharia) wish to be seen and known as pious.

Americans need to recognize that it is not just interpretation of jihad as a call to violence by radical Muslims that are a threat, because such literal interpretations are closely linked to strict adherence to sharia — and it is this adherence to Islamic law that raises legitimate questions as to some Muslims' capacity for assimilation or willingness to accept the constitutional divide between religion and a nation based on civil law.

Many Americans underestimate exactly what sharia represents when most stringently observed. It isn't just a dietary law involving rules for eating, like keeping kosher for observant Jews. It is pretty much the Islamic "theory of everything" and dictates the rules for life: religion, law, government, society, health, and family matters are all deliberately commingled under one roof. There is no separation of church and state; there is no civil law separate from religious law; there is no freedom of religion for non-Muslims; there is no right on the part of a Muslim to leave Islam in favor of another religion, or no religion at all. The result is an undeniable "us" versus "them" universe separating the pious observer from all others whose lifestyles and beliefs run counter to sharia.

It is one of the paradoxes and ironies of modern life that liberals and progressives — often the most vocal and impassioned about open borders, post-national society, and the importance of multi-culturalism — seem so willing to accept the seeds of their unmaking, because there is the potential for a short, sharp decline into tribalism and the very antithesis of progressive values by according too much credence to the idea that migrants need not assimilate or take on new Western values in order to live and thrive in the West. I am not by any means the first to have such thoughts; do a quick Google search on the words "multiculturalism tribalism" and you will see what I mean.

The failure to assimilate was brought into sharp relief to me a few months ago by a BBC news item about female genital mutilation (FGM), which is a growing problem in the United Kingdom (UK) where tens of thousands of women have been victimized by FGM. FGM is practiced by a few animist and Christian sects in selected parts of Africa, but it is endemic to many Muslim populations throughout the world.

From April to July of last year, over 1,000 new cases were reported in Britain; from July to September, another 1,385 were catalogued. It is so serious a problem that UK authorities have begun new programs to track and treat the victims — an unknown number of whom were subjected to the mutilation inside Britain. The victims are almost exclusively members of migrant families coming from Muslim societies where FGM is rampant, and although some arrive in the UK already having been victimized, others appear to be recent victims from migrant families that have transported the practice to their new environment, where they often live in insular bubbles that for all intents and purposes keep them separate from the society around them.

While FGM is clearly an unwanted facet of life brought to the UK's shores, British authorities have been experimenting with other things, like permitting some aspects of Islamic sharia law to be incorporated into the legal system — a kind of reverse assimilation, if you will — primarily in domestic matters involving marital relations, divorce, and the like. Many "salad bowl" progressives believe that such accommodation is somehow required to be sensitive to migrants' cultural origins.

The problem with this is twofold: First, from the non-assimilationist's point of view, why settle for a slice when it appears that with persistence you might end up with the whole pie? Second, from our Western point of view, the Islamic attitude toward divorce and child custody is weighted seriously in favor of the man, who may irrevocably divorce (subject to certain other restrictions such as abstinence from sexual relations with the wife) simply by saying "talaq" (I divorce you) three times over the course of several days. How many times he must say it depends on which sect of Islam you practice (see here and here ).

In sharia, marital relations are governed by the requirement that a wife be submissive, and the "law" permits the husband to beat her if she is not sufficiently obedient (although the size of the rod to be used is regulated and she is not to be "disfigured" or "made ugly", as explained by a Palestinian cleric in this video). Consequently, domestic abuse is a recurring and underreported problem in many Muslim households, because in unassimilated, insular households both husband and wife accept that it is his right to administer beatings for failure to be properly submissive.

Then there are other practices whose relationship to sharia may be questioned by some Islamic scholars, but nonetheless are rooted in Muslim cultures, such as honor killing and slavery. Although many Americans may be vaguely aware that radical terrorist groups such as Boko Haram and ISIS engage in slavery — most especially sex slavery — few understand that it derives its legitimacy from Koranic verses, and is practiced not just by terrorists. The New Yorker magazine published a revealing piece in September of 2014 about its continued prevalence and practice in Mauritania, including by Islamic clerics.

Finally, there is the penalty and fear of reprisals against Muslim apostates who abandon their religion, sometimes through conversion and sometimes simply because they no longer believe, or have progressed to the point that they believe, but also wish to separate religion from politics and not be under the thumb of clerics who guide and control all political and social thought. The reprisals may come from unruly crowds who kill the apostates and then go unpunished by police whose sympathies lie with the mob, or by the state itself, when the legal regimen under which the state operates is some form of sharia.

A surprising number of Islamic nations still have laws severely criminalizing apostasy or blasphemy, which are often a capital offense. Marjane Satrapi, in her autobiographical graphic novels "Persepolis" and "Persepolis II" describes life as a Muslim girl in Iran after takeover by the mullahs and its transformation into a theocracy. She tells the true story of a childhood acquaintance arrested as a self-declared communist (thus, an atheist) and sentenced to death. And while sharia prohibits the execution of virgins, this posed no conundrum for the religious authorities as they had faced the situation before: the girl, Niloufar, was forcibly "married" to, and deflowered by, one of her Revolutionary Guard prison tormentors and then, no longer being a virgin, was promptly executed. Her family was paid, postmortem, a "dowry" by the "husband" equating to about $5; receipt of the dowry by this man was how they came to know her fate.

Even after relocation to a new, western country, apostates can face danger. Not long ago, Breitbart carried a story on Muslims in Italy and England who have become Christians yet fear for their lives because they are surrounded by devout, unassimilated, Muslims in whose midst they live, almost as if they had never left their illiberal homeland.

And in the homeland itself, unbelievers are sometimes forcibly "converted". Worldwatch Monitor recently published findings from a nongovernmental organization (NGO) that show in Pakistan, "every year between 100 to 700 Christian women, 'usually between the ages of 12 and 25 are abducted, converted to Islam, and married to the abductor or third party'". (To its credit, it is a Muslim NGO that reported these findings, which is important to keep in mind in remembering that not all Muslims view their religious obligations in the same light.)

Permitting the import of sharia to our shores is to take a giant step back from the cultural and moral values that we generally share no matter whether we are conservatives or liberals within the context of our own societies. To do so is also in many ways a betrayal of Muslim women who believed they could throw off the bindings of chattel and escape the veil when they come to the West, because what sharia represents, at its most literal and militant, is the antithesis of modern Western thought.

While it should go without saying that not all Muslims take such a strict view toward sharia — as is evidenced by the Pakistani NGO cited above — I will say it, not just because if I don't I will be accused of bias, but because it is important in recognizing the many shades and varieties of thought in the Islamic world.

Indeed, it is moderate Muslims who carry a double burden because they are disdained, and sometimes targeted by, Islamic fundamentalists on one hand for not being sufficiently pious; and on the other, they are looked upon with suspicion by many Westerners in the United States, Europe, and elsewhere because so many evils have been perpetrated by radicals in the name of Islam. But this is a problem that has developed because of their violent co-religionists, not because we in the West have reason to apologize for our cultural values.

In fact, one of the strongest arguments I can think of in favor of administering some equivalent of an ideological test and enforcing our expectations that Muslims (indeed, all migrants) accept our way of life while in American society, is because there are moderate Muslims — including women, secularists, and gay men and women — who seek to escape the confinements of a society in which they cannot thrive, and may be at risk of death. Are they not entitled to liberate themselves from those constraints upon arrival? They need not fear an ideological litmus test, and should welcome it as proof positive that they may find their own path here, free from reprisal or condemnation.

In the context of immigration, if we in the United States are to continue to accept practicing Muslims, there must be a clear commitment to assimilation on all sides. This means levying the demand that, both before and after entry, they accept that our society maintains a distinct separation of church and state; that all persons are free to practice — or decline to practice — any religion, and that there is no such thing as an apostate; and, most significantly, we recognize the preeminent rule of civil, not religious, law and government.

In sum, we must reject sharia and its all-encompassing, constitutionally violative notions of government and society as revolving solely around Islam. We must not tolerate intolerance. To do so is to descend into tribalism. One way to do that, without rejecting all Muslims, is by imposing ideological expectations and boundaries on those who wish to live within our society.

Some have suggested that many people will lie. That's self-evident, but hardly an argument for not undertaking a course of action. People commit all kinds of fraud, all the time, but it doesn't, and shouldn't, stop government officials from imposing anti-fraud regimes, because by obliging individuals to acknowledge responsibilities and limits, and to undertake a course of action and lifestyle consistent with constitutional principle, you have a basis on which to hold them accountable when they don't.

A final word: Because we should expect the same of all migrants, why limit such an ideological test or affirmation solely to Muslim immigrants?