As the Pope makes his visit to Muslim Turkey, indications continue that the enormous tension between Christianity and Islam will play out through much of this century, as part of prophesied events, with three essential questions for Catholics to consider.

The first: how far will Islam penetrate?

Many are the indications that a decade down the line, it will be far more pervasive than even now. Currently 21 percent of the world's populace subscribes to this faith, or 1.3 billion, versus 33 percent or 2.1 billion who are Christians (about half that Catholics).

But in many Christian nations, a low birth rate from abortion and widespread use of contraception is causing a decrease in population -- such that certain nations in Europe will see Muslims all but assume control by the mid-point or end of the century. At the current rate, Russia will be more than half Muslim by 2050. In Europe, the birth rate for Muslims is three times that of non-Muslims.

No one knows the precise number of Muslims in the United States. Estimates range from one to seven million. That's versus 69 million Catholics.

There is thus no near-term threat that the U.S. will turn into a Muslim nation, but those following Islam have been treated as a persecuted minority in the U.S. and in certain instances have been able to publicly display their religion in venues where Christians cannot. Moreover, Muslims tend to be more religiously fervent. In Detroit, recently, a Catholic church was sold and converted into a mosque.

In Canada, the percentage of Christians is in rapid decline, dropping at 0.9 percentage points per year. Some fear that those who can rightly be identified as Christians will be in the minority by 2023, with "secularists" (neither Christian nor Muslim) dominating.

Elsewhere, there is the growing trend toward Islam, including in Mexico. The situation is hardly bleak at this point, but the world will see Muslims take over major countries if the trends continue. Should China open itself to religion and if Muslims take a foothold there, there is no telling how the dynamic will evolve.

Which brings us to the second issue: tension between Muslims and Catholics.

Should Muslims and Christians find common ground?

The Vatican says yes -- while criticizing the violent aspect of many Muslims, as seen most tellingly with Pope Benedict at Regensburg, Germany, when he created a furor by mentioning the religion in the same breath as "evil." John Paul II noted that the theology of Islam is "very distant from Christianity" but that "the religiosity of Muslims deserves respect." He once visited a mosque, as will Benedict.

Both Islam and Catholicism believe in one God, cite the struggle with Satan, and honor the Blessed Mother. That's what they have in common -- and something that could be built upon, along with Muslim opposition to secularism. But Islam denies the divinity of her Son, which many Catholics cite as a trait of anti-christ.

Might a personage of evil -- an anti-christ -- rise out of such ranks? Or will Catholicism and Islam join forces against the deception of their common foe (the devil)?

At this point, the tension is high and intensifying. It is an age-old conflict and was fought across southern Europe just a few short centuries ago. Has another such war begun, this time on a global scale -- and was its "Pearl Harbor" on September 11?

Right after the terrorist attacks, unusual displays of the northern lights were seen in a way that recalled, if to a lesser extent, the aurora borealis that seer Lucia dos Santos of Fatima saw as a sign announcing the Second World War. There is mystical significance to Turkey, where the early Christians struggled against paganism and where there is what is believed to be the final home of the Virgin Mary (left).

Will commonality prevail? Tensions between Muslims and Christians have been greatly aggravated by the war in Iraq, which is spilling over into neighboring states. There is currently the possibility of three civil wars at the same time in the Middle East -- and a future of nuclear weapons.

Whatever attributes of goodness can be culled from this faith -- which has many devout, honest believers, people who truly want to do what is right, and deserve respect -- we come to the third question: is there something inherently evil about Islam, something deceptive, something that makes all the current posturing and attempts at diplomacy irrelevant?

Last week, evangelical firebrand Pat Robertson said anything but Christianity is demonic. The Pope is seeking reconciliation -- while firmly standing for Christian principles of peace.

One thing is clear: Islam is on the march and is not shy about the use of violence. The Israeli conflicts speak for themselves, but Muslim tensions also have been at the root of numerous other conflicts: the Soviet-Afghanistan war, the Chechen battles, conflicts in Indonesia, battling in the Philippines, skirmishes between India and Pakistan, and many conflicts -- such as Darfur -- in Africa. Ethiopia is currently poised for an Islamist war.

The U.N. humanitarian chief said a "dramatic deterioration" of the situation in Sudan's Darfur region has left four million people in desperate need of humanitarian assistance. That is not a good fruit.

Bush had called Iran part of the "axis of evil" and now the Iranian leader has called President Bush "evil." Neither approach is helpful. The leader, Mahmoud Ahmadinejad, has indicated that he believes Muslims must make way for a messianic person or "Mahdi" who is soon to arrive and that such preparation involves "chaos."

The high-profile president of Iran says that the world is rapidly becoming "Ahmadinejadized," with global leaders following in his footsteps. "I have traveled to all the continents except for one, and I know what is going on out there. Everybody is eager to hear the Iranian people's message," the Aftab-Yazd newspaper quoted the president as saying. He added that Iran's "two big missions are constructing the country and introducing a model for humanity."

Could a Muslim leader thought to be the great Mahdi be an anti-christ?

He would certainly unite many Muslims who are currently in conflict with each other. The Mahdi or "Guided One" ) in Islamic eschatology is the prophesied redeemer of Islam, who will change the world into a perfect Islamic society alongside the "Prophet" Jesus before Yaum al-Qiyamah (literally "Day of the Resurrection").

For decades now, Catholic prophecy has spoken of persecution. Will it come at the hands of Muslims -- who routinely imprison and execute Christians, and in some nations have made it illegal to hold a Christian prayer meeting or even own a Bible?

Long before September 11, a Muslim named Osama Bin Laden plotted to kill John Paul II in the Philippines, and the gunman who tried to assassinate the Pope in 1981 in Rome, Mehmet Agca, was Turkish.

It thus makes it difficult to see the future as rosy, when it comes to interfaith cooperation. This may be both the persecution people expect and the next great war. And this is why Pope Benedict's trip is of great significance. For good or ill, it may be an omen.

Will we stand both strong and yet in conciliation?

And will Muslims appreciate it?

While the vast majority are good, law-abiding people in the U.S., the radicalism can be chilling.

Father Andrea Santoro knelt in prayer at a pew in the rear of Santa Maria Catholic Church in Trabzon, Turkey. "The Bible on the nearby lectern lay open at the Book of John, Chapter 16, in which Jesus tells his disciples of his forthcoming death -- and the challenges they will face after he is gone," says a news account. In it, Jesus warns that "the hour is coming... when everyone who kills you will think he is offering worship to God."

This occurred ten months ago. "As Santoro prayed, 15-year-old Oguzhan Akdin stepped toward the front door of the church and once inside, the Turkish boy raised his handgun and shot the kneeling priest twice," says the report. "The boy turned and ran. The priest collapsed on the marble floor of the church, dying almost instantly."

Meanwhile, in the U.S.: a high-school Spanish teacher resigned his position recently after placing hidden messages inside a word-search puzzle calling on Allah to destroy America, which he called the "body of evil that is making human life so miserable."