Horrific acts of violence are currently being carried out in several areas of the world in the name of Islam, from Iraq and Syria to Nigeria, Afghanistan, and Pakistan, to provide a partial list. And, of course, Islamic terrorism is not a new phenomenon.
For well over a decade now, there has been a debate about whether Islam and its key holy text, the Qur'an, are different from other faiths and their sacred texts in that Islam and the Qur'an are allegedly uniquely belligerent, inspiring if not commanding violence toward others, and therefore are a significant contributing cause (no one claims the sole cause) for the disproportionate share of religious terrorism attributable to Islamists. Certainly the terrorists themselves invoke Qur'anic texts to justify their violence.
As an atheist, I also consider myself an empiricist, so I decided that there was no substitute for actually reading the Qur'an. I have now read about 40 percent of it (the first 10 suras, or chapters, and some scattered chapters that I thought interesting). This is probably more than I've read of the Bible. In preparation for my reading of the Qur'an, I also read The Story of the Qur'an by Ingrid Mattson, an academic who describes herself as a "faithful Muslim," and reacquainted myself with the history of the period in which Muhammad lived. As with the Bible, there are various controversies surrounding the Qur'an, in terms of its authorship, the date(s) of its composition, the reliability of various versions, and so forth. None of these controversies affects my analysis here, and to avoid unnecessary complications, I'll assume it was Muhammad who transmitted the revelations that constitute the Qur'an.
Defensiveness
I would characterize the predominant tone of the Qur'an not as belligerent but as defensive. From the second sura onward (the first sura is essentially a ritual prayer), verse after verse emphasizes the critical importance of believing in the revelations while coupling this with warnings about those who mock and laugh at Muhammad (e.g., 2:2-21; 2:75-82; 2:87-92; 2:208-212; 3:10-13; 3:116-117; 3:176-186). To quote one passage (I use the translation by M.A.S. Abdel Haleem, published by Oxford University Press):
So when they come to you, they argue with you: the disbelievers say, "These are nothing but ancient fables," and tell others not to listen [to the Qur'an] ... But they ruin no one but themselves ... If you could only see, when they are made to stand before the Fire, how they will say, "If only we could be sent back, we would not reject the revelation of our Lord, but be among the believers." (6: 25-27)
The text exudes insecurity masked with bravado: It's a hard sell by a person who is attempting to persuade others in the face of some withering criticism while simultaneously trying to retain his own confidence in the product. Here's Allah to Muhammad: "[Prophet], do not be grieved by those who are quick to disbelieve" (3:176).
The Competing Religions
And there were competing religious product lines, namely tribal polytheism, Christianity, and Judaism. With respect to these competing beliefs, Muhammad made a decisive, prescient move. Rater than rejecting the Jewish and Christian revelations, he incorporated them into his message. (A subsequent prophet, Joseph Smith, made a similar move, as have a number of others.) Sure, the Jewish and Christian revelations had been corrupted -- that's one reason Allah needed Muhammad to set things straight -- but they were divine revelations. This allowed Muhammad to build on the Jewish-Christian base and lend some credence to his own message while providing him with another line of defense: Just as Moses, Jesus, and other prophets were mocked, he is being mocked (e.g., 2:87; 3:52-54; 6:10). What else one would expect?
It also established a special relationship between Muslims and Jews and Christians, as they were grouped as People of the Book, with at least some passages in the Qur'an indicating that, assuming Christians and Jews do good, they will also "have their rewards with their Lord" (2:62). Other passages are more equivocal about what Christians and Jews can expect from Allah, and further passages are highly critical of Jews and Christians, cautioning Muslims not to take them as allies (5:51), conditioning their acceptance in Muslim society on payment of special taxes (9:29-35), and warning Muhammad, "You [Prophet] are sure to find that the most hostile to the believers are the Jews and those who associate other deities with God" (5:82). So there is enough textual warrant to justify a wide range of attitudes and conduct toward Christians and Jews. That said, during the medieval and early modern periods, Christians and Jews generally received better treatment in Muslim lands than Muslims and Jews received in Christian lands.
The real focus of Muslim ire, and the provenance of most passages urging combat and the killing of "disbelievers," were the polytheistic tribes who resisted Muhammad and persecuted his followers. There was open warfare between these groups, which, as is well known, resulted in Muhammad's flight to Medina and his eventual triumphant return to Mecca. The most cold-blooded partial verse may be "Kill them wherever you encounter them" (2:191), which is oft-cited as evidence of Islam's intolerance. But the rest of this verse and passage indicates that this references the tribes who were persecuting Muhammad's followers, and furthermore counsels that fighting is to stop when persecution stops: "If they cease hostilities, there can be no [further] hostility, except toward aggressors" (2:191-193).
So, as with much of the Qur'an, and as with other holy texts, there is room for divergent interpretations, especially in light of differing understandings of what constitutes "persecution."
So Is the Qur'an Inherently More Incendiary Than the Bible?
If Muhammad thought Allah was instructing him to be tough with disbelievers, he may be forgiven for not considering this an unusual directive given God's near-annihilation of humanity through the Noachian Flood and the genocide God ordered the ancient Israelites to carry out when they advanced into the Promised Land. God mercilessly called for the extinction of the Amorites, the Hittites, the Canaanites, and many other peoples (e.g., Deuteronomy 7:1-2). When those walls of Jericho came a-tumblin' down, the result was a divinely sanctioned slaughter of every living thing in the city (Joshua 6:16-21). Passages such as these have been used in the past to justify the killing of heretics and other undesirables. Some Jewish extremists cite them even today to justify ethnic cleansing, although the predominant means of dealing with these passages now is either to ignore them in embarrassed silence or to creatively interpret them so that their message is a symbolic one about God standing behind his people or some other such gloss more congenial to contemporary sensibilities.
If the Qur'an seems more relentlessly violent, it's in part a function of its structure. Rather than a chronological narrative, it's a set of admonitions and instructions, repeated often, so the effect produced can be one of adamant hostility to those who reject Muhammad's revelations, whereas the murder of those who stood in the way of the Israelites is part of a larger, unfolding story.
The Real Problems
Objectively, there's no denying that today Islamic extremism poses more of a threat than other types of religious fanaticism. There are complex historical, social, and cultural reasons for this, including the greater prevalence of religious fundamentalism generally in the Islamic world. Islam has yet to have its Enlightenment, and support for a truly secular state remains a minority view in Islam. But this is not a matter of the text of the Qur'an being inherently more susceptible to intolerant interpretations than the Bible.
Of course, an even more fundamental problem, affecting all religions, as well as those atheist ideologies that treat some person or text as authoritative (for example, Mao's "Little Red Book," once the most printed book in the world), is the dogmatic mindset that there is a message that one must accept on pain of being deemed less worthy of respect, if not an outright enemy. No prophet, no Dear Leader, has a privileged pipeline to the Truth. We need to stop looking "above" for directives that we can impose on others and instead look and listen to each other for answers. Quoting sacred texts and then squabbling about their proper interpretation leads nowhere but to more conflict. Reasoning together about how best to address our shared concerns and regarding the views of all of us as entitled to equal consideration is the only way we'll ever achieve peace.