Clearly related to this is the basic division of mankind as perceived in Islam. Most, probably all, human societies have a way of distinguishing between themselves and others: insider and outsider, in-group and out-group, kinsman or neighbor and foreigner. These definitions not only define the outsider but also, and perhaps more particularly, help to define and illustrate our perception of ourselves.
In the classical Islamic view, to which many Muslims are beginning to return, the world and all mankind are divided into two: the House of Islam, where the Muslim law and faith prevail, and the rest, known as the House of Unbelief or the House of War, which it is the duty of Muslims ultimately to bring to Islam. But the greater part of the world is still outside Islam, and even inside the Islamic lands, according to the view of the Muslim radicals, the faith of Islam has been undermined and the law of Islam has been abrogated. The obligation of holy war therefore begins at home and continues abroad, against the same infidel enemy.
Like every other civilization known to human history, the Muslim world in its heyday saw itself as the center of truth and enlightenment, surrounded by infidel barbarians whom it would in due course enlighten and civilize. But between the different groups of barbarians there was a crucial difference. The barbarians to the east and the south were polytheists and idolaters, offering no serious threat and no competition at all to Islam. In the north and west, in contrast, Muslims from an early date recognized a genuine rival—a competing world religion, a distinctive civilization inspired by that religion, and an empire that, though much smaller than theirs, was no less ambitious in its claims and aspirations. This was the entity known to itself and others as Christendom, a term that was long almost identical with Europe.
The struggle between these rival systems has now lasted for some fourteen centuries. It began with the advent of Islam, in the seventh century, and has continued virtually to the present day. It has consisted of a long series of attacks and counterattacks, jihads and crusades, conquests and reconquests. For the first thousand years Islam was advancing, Christendom in retreat and under threat. The new faith conquered the old Christian lands of the Levant and North Africa, and invaded Europe, ruling for a while in Sicily, Spain, Portugal, and even parts of France. The attempt by the Crusaders to recover the lost lands of Christendom in the east was held and thrown back, and even the Muslims' loss of southwestern Europe to the Reconquista was amply compensated by the Islamic advance into southeastern Europe, which twice reached as far as Vienna. For the past three hundred years, since the failure of the second Turkish siege of Vienna in 1683 and the rise of the European colonial empires in Asia and Africa, Islam has been on the defensive, and the Christian and post-Christian civilization of Europe and her daughters has brought the whole world, including Islam, within its orbit.
For a long time now there has been a rising tide of rebellion against this Western paramountcy, and a desire to reassert Muslim values and restore Muslim greatness. The Muslim has suffered successive stages of defeat. The first was his loss of domination in the world, to the advancing power of Russia and the West. The second was the undermining of his authority in his own country, through an invasion of foreign ideas and laws and ways of life and sometimes even foreign rulers or settlers, and the enfranchisement of native non-Muslim elements. The third—the last straw—was the challenge to his mastery in his own house, from emancipated women and rebellious children. It was too much to endure, and the outbreak of rage against these alien, infidel, and incomprehensible forces that had subverted his dominance, disrupted his society, and finally violated the sanctuary of his home was inevitable. It was also natural that this rage should be directed primarily against the millennial enemy and should draw its strength from ancient beliefs and loyalties.