Islam was the last of the three great monotheistic religions to emerge from the Middle East and go global. Today it has about 1.2 billion adherents (or 19% of the world's population), making it the world's second most popular faith after Christianity (2 billion). Contrary to popular assumption, only 18% of Muslims today are Arab; 30% live in the Indian subcontinent, 20% in Sub-Saharan Africa and 16%, or more than 200 million, in Indonesia alone. The faith is also one of the world's fastest growing, mostly by dint of reproduction rather than conversion; by some estimates it will account for a quarter of the global population by 2050. How many Muslims live in the U.S. is a politically loaded question; the number has been estimated at anywhere between 2 and 9 million. Very possibly U.S. Muslims outnumber Episcopalians (2.3 million) and they may be as populous as Jews (5.9 million).
Islam, which in Arabic means submission (i.e., to God's will), is marked by two primary theological points: an extreme stress on God's omnipotence and indivisibility, and an understanding that his final and perfect revelation to humanity is a series of statements transmitted by an angel (in Arabic) to the prophet Mohammed between the years 609 and 632, which were subsequently compiled as the holy Koran. Islam recognizes a number of previous prophets, such as Abraham, Moses and Jesus, but maintains that their messages were either partial or garbled by their followers.
The Koran's style is not as linear or straightforward as that of the Jewish and Christian bibles, but from it and from the example of Mohammed, who was considered a perfect believer, Islam derived a way of belief and life. The faith's five "pillars" of religious practice are the recitation of the shahada ("There is no God but Allah and Mohammed is his prophet"), prayer five times a day, charity, fasting during the holy month of Ramadan, and a pilgrimage, if possible, to the holy city of Mecca, Arabia. Notably absent from the list is the pursuit of warfare against infidels, despite the claims of some Islamophobes (and of some radical Islamists, who call it the Sixth Pillar).
From the beginning, however, Islam was more than a creed or practice: it understood itself as a community with legal, political and military aspects. The result was one of the most spectacular early successes in the annals of organized religion. By Mohammed's death, the faith controlled the Arabian peninsula. A little more than a century later, a unified Islamic state under successors to Mohammed known as the caliphs had conquered a large slice of the known world, reaching from Spain's Atlantic coast to the Indus River.
It constituted one of the great world civilizations, making major contributions to Western culture (from the development of algebra to the preservation of Greek philosophy) at a time when Europe was still mired in the Dark Ages. Over centuries, however, it suffered both political and theological schisms. The unified community split into competing caliphates, which eventually disappeared altogether as the West colonized previously Muslim territories and secular governments arose even in nations with Muslim majorities.
Theologically, the most fundamental split was between Sunni and Shi'a Islam. Initially an argument about who should be Mohammed's political heirs, it became far more traumatic in 680 with the martyrdom of Hussein, the son of Mohammed's son-in-law and the Shiite claimant. Repudiating Sunni leaders, Shiites believed in a chain of mystically infallible Imams, ending in 874 with the disappearance of the 12th Imam, expected to return as a messiah-like figure at the end of time. (Subsequent Shiite religious leaders have been regarded as his "deputies.") Today various Shiite subgroups make up 10% to 15% of all Muslims, including the overwhelming majority in Iran, now a Shi'a theocracy, and more than 60% in Iraq, where the Sunni/Shi'a distinction is a crucial social and political fault-line.
Islam has undergone dozens of other schisms, splits and outgrowths. One of the best known to non-Muslims is its mystic variant, Sufism, which bears some resemblance to Jewish and Christian mysticism and produced both whirling dervishes and the poet Rumi.
Two more recent, and controversial, developments are Wahhabism and Islamism. Wahhabism started in the 1700s as a starkly puritan movement. It was central to the foundation of Saudi Arabia, which subsequently used oil revenues to promote it globally (Afghanistan's Taliban are Wahhabi). Islamism is an Egyptian-rooted Muslim political movement aimed at replacing secular governments in Muslim-majority countries with those guided by religious law, or sharia. Each movement has peaceable manifestations: not all Wahhabis are warlike, and both the current ruling party in Turkey and the powerful Muslim Brotherhood in Egypt are or have recently been Islamists. But a Wahhabi/Islamist mix figures prominently in the cobbled-together ideology of Al Qaeda and other groups engaged in terrorism, an ideology that seems blatantly to contradict sharia.
As with any religion followed by millions, Islam has been invoked by both saints and rogues, yielded both solace and bitterness. The persistence of "Islamic" terrorism since 9/11 and the increasing restiveness of Muslim minorities in Europe have prompted critics, most recently Pope Benedict XVI, to urge an examination of the religion for possible roots of violence. They would be wise, however, to seek secular roots as well, and to understand militancy as just one voice (and a tiny if shrill minority) in an enormous, decentralized amalgam of believers and sub-philosophies.
—David Van Biema