The stage is set for the Republican presidential debate, hosted by CNN, at the Venetian hotel in Las Vegas on Tuesday. (Robyn Beck/AFP via Getty Images)

The Republican debate takes place after weeks of sometimes troubling rhetoric about the presence of refugees and Muslims in the United States.

After last month's terror attacks in Paris, scrutiny fell on U.S. plans to provide sanctuary to about 10,000 Syrian refugees. A host of governors, mostly Republicans, declared that they would try to halt arrivals of Syrian refugees in their states. GOP presidential candidates joined the chorus, some rejecting allowing any refugees in, while others proposed admitting only Syrian Christians.

This was followed by a declaration from Donald Trump, the Republican front-runner, insisting that arrivals of Muslims be stopped altogether for security concerns. (Never mind that no country in the world blocks arrivals at its borders on the basis of religion, as WorldViews noted last week.)

Given the heated atmosphere that surrounds Tuesday's debate, here's a primer on the two rather large categories that may fall in the spotlight.

What you should know about Muslims

Well, there are a lot of them — about 1.6 billion people, according to a 2011 Pew survey. The size of the global Muslim population is expected to match that of Christians by 2050. Of course, this doesn't account for the vast diversity within the religion, whose adherents belong to a huge range of sects and traditions, speak myriad languages and sport every complexion on this planet.

Moreover, and contrary to the picture of the "Muslim world" often painted in the West, the majority of the world's Muslim population is not ethnically Arab and does not live in the Middle East, but in South and Southeast Asia. There are at least twice as many Muslims in India, for example, than in any nation in the Middle East.

While the world's Muslim population is certainly big, many people in Western countries imagine the Muslim communities in their midst to be far larger than they actually are, as this Ipsos survey from last year found. Respondents in a host of European countries, as well as the United States and Australia, all believed that the population of Muslims in their societies was exponentially greater than in the reality — a sign, perhaps, of fears about Islamist infiltration and Muslim integration.

Security concerns about Muslims writ large abound in numerous Western countries, where populist, far-right politicians and political parties have traded on a thinly veiled Islamophobia to score votes.

Despite the current ravages of extremists such as the Islamic State, the connection between Muslims — an enormous group of human beings who live in various places in the world — and terrorism is also inflated. Ninety-four percent of terrorist acts committed in the United States since 1980 have been carried out by non-Muslims, according to the FBI. In the past five years, fewer than 2 percent of all terrorist attacks in Europe have been "religiously motivated," according to European Union data.

Trump invoked a widely discredited poll to suggest that large numbers of Muslims harbored views sympathetic to the jihadists — who, in any context, comprise a radical fringe. Trump's supposition — that all Muslims should be kept out because of the putative threat of a minority who happen to share their faith — is bigotry, plain and simple. It ignores, of course, the overwhelming majority of Muslims who are as removed and as innocent as anyone else from the plots of certain extremist organizations.

What you need to know about Syrian refugees

The chaos in Syria is an epochal calamity. One of the Middle East's most venerable societies has been ripped apart by a brutal civil war, which has assumed a tragically sectarian character in recent years. More than 250,000 Syrians have perished in the conflict, and about 11 million people, or roughly half the country's population, have been displaced.

According to recent U.N. data, there are nearly 4.4 million Syrian refugees, who have been forced to flee their country because of the war. The vast majority of these people are in countries neighboring Syria, chiefly Lebanon, Iraq and Turkey.

The refugee crisis is a far greater burden and dilemma in these places than it is in the West, which has seen a comparatively small influx of Syrians taking the dangerous journey toward what they hope is a better, safer life. Syrians make up roughly a quarter of Lebanon's population; Turkey claims it has sheltered up to 2.2 million Syrians and has provided free health care and education to many refugees, at the cost of billions of dollars in unbudgeted funds.

Because of a 1951 U.N. convention, the international community has an explicit responsibility toward providing relief and sanctuary to refugees. Western governments are acting not just out of generosity but obligation.

Yet popular opinion in Europe and the United States is poisoned against Syrian refugees because of the perceived ideological and security threat they possess. This, as WorldViews has noted a number of times, carries echoes of the past, when Americans and others saw Jews fleeing fascist Europe as communists and fifth columnists.

The hysteria around refugees spiked in the wake of the tragic events in Paris. A fake Syrian passport was found at the scene of one of the attacks, but so far all the assailants identified by French authorities have been European nationals.

Another right-wing talking point suggests that the bulk of the refugees are single and male; this is simply not true. According to U.N. data, more than 50 percent of registered refugees are women. Females make up 23.9 percent of refugees ages 18 to 59, while men comprise 21.8 percent.

The United States, it should be noted, has one of the most extensive and rigorous vetting processes for refugees in the world. As The Washington Post's Fact Checker reported, of the hundreds of thousands of refugees admitted by the United States in recent years, only a handful were later arrested over terrorism concerns. (Even then, there is no necessary connection between their refugee status and subsequent potential radicalization.) Here's the Fact Checker's Michelle Ye Hee Lee:

A State Department spokesperson said of the nearly 785,000 refugees admitted through the U.S. Refugee Admissions Program since 9/11, “only about a dozen — a tiny fraction of one percent of admitted refugees — have been arrested or removed from the U.S. due to terrorism concerns that existed prior to their resettlement in the U.S.  None of them were Syrian.”

In Canada, the new Liberal government of Prime Minister Justin Trudeau has shrugged off domestic fears to welcome the first batch of about 25,000 Syrian refugees expected to be resettled by early next year. Trudeau personally met some of the recent arrivals at the airport last week.

"They step off the plane as refugees, but they walk out of this terminal as permanent residents of Canada with social insurance numbers, with health cards and with an opportunity to become full Canadians," Trudeau said. "This is something that we are able to do in this country because we define a Canadian not by a skin color or a language or a religion or a background, but by a shared set of values, aspirations, hopes and dreams that not just Canadians but people around the world share."

That's a worldview and sense of identity that most Americans, even in an election year, probably also welcome and understand.

Related on WorldViews

Canada races ahead of U.S. to welcome Syrian refugees

Donald Trump is helping the Islamic State

Yes, the comparison between Syrian and Jewish refugees matters