It is very hard to prove Islam is a sect of Christianity.

John Damascene, for his part, believed that Islam was the last, great Christological heresy--and being right there in the midst of it, he may have known something.

THE GREAT HERESIES

by Hilaire Belloc

Chapter Four

The Great and Enduring Heresy of Mohammed

It might have appeared to any man watching affairs in the earlier years of the seventh century_say from 600 to 630_that only one great main assault having been made against the Church, Arianism and its derivatives, that assault having been repelled and the Faith having won its victory, it was now secure for an indefinite time.

Christendom would have to fight for its life, of course, against outward unchristian things, that is, against Paganism. The nature worshippers of the high Persian civilization to the east would attack us in arms and try to overwhelm us. The savage paganism of barbaric tribes,
Scandinavian, German, Slav and Mongol, in the north and centre of Europe would also attack Christendom and try to destroy it. The populations subject to Byzantium would continue to parade heretical views as a label for their grievances. But the main effort of heresy, at least, had failed_so it seemed. Its object, the undoing of a united Catholic civilization, had been missed. The rise of no major heresy need henceforth
be feared, still less the consequent disruption of Christendom.

By A.D. 630 all Gaul had long been Catholic. The last of the Arian generals and their garrisons in Italy and Spain had become orthodox. The Arian generals and garrisons of Northern Africa had been conquered by the orthodox armies of the Emperor.

It was just at this moment, a moment of apparently universal and permanent Catholicism, that there fell an unexpected blow of overwhelming magnitude and force. Islam arose_quite suddenly. It came out of the desert and overwhelmed half our civilization.

Islam_the teaching of Mohammed_conquered immediately in arms. Mohammed's Arabian converts charged into Syria and won there two great battles, the first upon the Yarmuk to the east of Palestine in the highlands above the Jordan, the second in Mesopotamia. They went on to
overrun Egypt; they pushed further and further into the heart of our Christian civilization with all its grandeur of Rome. They established themselves all over Northern Africa; they raided into Asia Minor, though they did not establish themselves there as yet. They could even occasionally threaten Constantinople itself. At last, a long lifetime after their first victories in Syria, they crossed the Straits of
Gibraltar into Western Europe and began to flood Spain. They even got as far as the very heart of Northern France, between Poitiers and Tours, less than a hundred years after their first victories in Syria_in A.D. 732.

They were ultimately thrust back to the Pyrenees, but they continued to hold all Spain except the mountainous north-western corner. They held all Roman Africa, including Egypt, and all Syria. They dominated the whole Mediterranean west and east: held its islands, raided and left armed settlements even on the shores of Gaul and Italy. They spread mightily throughout Hither Asia, overwhelming the Persian realm. They were an increasing menace to Constantinople. Within a hundred years, a main part of the Roman world had fallen under the power of this new and strange force from the Desert.

Such a revolution had never been. No earlier attack had been so sudden, so violent or so permanently successful. Within a score of years from the first assault in 634 the Christian Levant had gone: Syria, the cradle of the Faith, and Egypt with Alexandria, the mighty Christian See. Within a lifetime half the wealth and nearly half the territory of the
Christian Roman Empire was in the hands of Mohammedan masters and officials, and the mass of the population was becoming affected more and more by this new thing.

Mohammedan government and influence had taken the place of Christian government and influence, and were on the way to making the bulk of the Mediterranean on the east and the south Mohammedan.

We are about to follow the fortunes of this extraordinary thing which still calls itself Islam, that is, "The Acceptation" of the morals and simple doctrines which Mohammed had preached.

I shall later describe the historical origin of the thing, giving the dates of its progress and the stages of its original success. I shall describe the consolidation of it, its increasing power and the threat which it remained to our civilization. It very nearly destroyed us. It kept up the battle against Christendom actively for a thousand years, and
the story is by no means over; the power of Islam may at any moment
re-arise.

But before following that story we must grasp the two fundamental things_<first>, the nature of Mohammedanism; second, the essential cause of its sudden and, as it were, miraculous success over so many thousands of miles of territory and so many millions of human beings.

Mohammedanism was a <heresy>: that is the essential point to grasp before going any further. It began as a heresy, not as a new religion. It was not a pagan contrast with the Church; it was not an alien enemy. It was a perversion of Christian doctrine. It vitality and endurance soon gave it the appearance of a new religion, but those who were contemporary with its rise saw it for what it was_not a denial, but an adaptation and a misuse, of the Christian thing. It differed from most (not from all)
heresies in this, that it did not arise within the bounds of the Christian Church. The chief heresiarch, Mohammed himself, was not, like most heresiarchs, a man of Catholic birth and doctrine to begin with. He sprang from pagans. But that which he taught was in the main Catholic doctrine, oversimplified. It was the great Catholic world_on the frontiers
of which he lived, whose influence was all around him and whose
territories he had known by travel_which inspired his convictions. He came of, and mixed with, the degraded idolaters of the Arabian wilderness, the conquest of which had never seemed worth the Romans' while.

He took over very few of those old pagan ideas which might have been native to him from his descent. On the contrary, he preached and insisted upon a whole group of ideas which were peculiar to the Catholic Church and distinguished it from the paganism which it had conquered in the Greek and Roman civilization. Thus the very foundation of his teaching
was that prime Catholic doctrine, the unity and omnipotence of God. The attributes of God he also took over in the main from Catholic doctrine: the personal nature, the all-goodness, the timelessness, the providence of God, His creative power as the origin of all things, and His sustenance of all things by His power alone. The world of good spirits and angels and of evil spirits in rebellion against God was a part of the teaching, with a chief evil spirit, such as Christendom had recognized. Mohammed preached with insistence that prime Catholic doctrine, on the human side_the immortality of the soul and its responsibility for actions in this life, coupled with the consequent doctrine of punishment and reward after death.

If anyone sets down those points that orthodox Catholicism has in common with Mohammedanism, and those points only, one might imagine if one went no further that there should have been no cause of quarrel. Mohammed would almost seem in this aspect to be a sort of missionary, preaching and
spreading by the energy of his character the chief and fundamental doctrines of the Catholic Church among those who had hitherto been degraded pagans of the Desert. He gave to Our Lord the highest reverence, and to Our Lady also, for that matter. On the day of judgment (another Catholic idea which he taught) it was Our Lord, according to Mohammed, who would be the judge of mankind, not he, Mohammed. The Mother of Christ, Our Lady, "the Lady Miriam" was ever for him the first of womankind. His followers even got from the early fathers some vague hint of her Immaculate Conception.[1]

But the central point where this new heresy struck home with a mortal blow against Catholic tradition was a full denial of the Incarnation.

Mohammed did not merely take the first steps toward that denial, as the Arians and their followers had done; he advanced a clear affirmation, full and complete, against the whole doctrine of an incarnate God. He taught that Our Lord was the greatest of all the prophets, but still only a prophet: a man like other men. He eliminated the Trinity
altogether.

With that denial of the Incarnation went the whole sacramental structure. He refused to know anything of the Eucharist, with its Real Presence; he stopped the sacrifice of the Mass, and therefore the institution of a special priesthood. In other words, he, like so many other lesser heresiarchs, founded his heresy on simplification.

Catholic doctrine was true (he seemed to say), but it had become encumbered with false accretions; it had become complicated by needless man-made additions, including the idea that its founder was Divine, and the growth of a parasitical caste of priests who battened on a late, imagined, system of Sacraments which they alone could administer. All those corrupt accretions must be swept away.

There is thus a very great deal in common between the enthusiasm with which Mohammed's teaching attacked the priesthood, the Mass and the sacraments, and the enthusiasm with which Calvinism, the central motive force of the Reformation, did the same. As we all know, the new teaching
relaxed the marriage laws_but in practice this did not affect the mass of his followers who still remained monogamous. It made divorce as easy as possible, for the sacramental idea of marriage disappeared. It insisted upon the equality of men, and it necessarily had that further factor in which it resembled Calvinism_the sense of predestination, the sense of
fate; of what the followers of John Knox were always calling "the immutable decrees of God."

Mohammed's teaching never developed among the mass of his followers, or in his own mind, a detailed theology. He was content to accept all that appealed to him in the Catholic scheme and to reject all that seemed to him, and to so many others of his time, too complicated or mysterious to be true. Simplicity was the note of the whole affair; and since all heresies draw their strength from some true doctrine,
Mohammedanism drew its strength from the true Catholic doctrines which it retained: the equality of all men before God_"All true believers are brothers." It zealously preached and throve on the paramount claims of justice, social and economic.

Now, why did this new, simple, energetic heresy have its sudden overwhelming success?

One answer is that it won battles. It won them at once, as we shall see when we come to the history of the thing. But winning battles could not have made Islam permanent or even strong had there not been a state of affairs awaiting some such message and ready to accept it.

Both in the world of Hither Asia and in the Graeco-Roman world of the Mediterranean, but especially in the latter, society had fallen, much as our society has today, into a tangle wherein the bulk of men were disappointed and angry and seeking for a solution to the whole group of
social strains. (emphasis mine) There was indebtedness everywhere; the power of money and consequent usury. There was slavery everywhere. Society reposed upon it, as ours reposes upon wage slavery today. There was weariness and discontent with theological debate, which, for all its intensity, had
grown out of touch with the masses. There lay upon the freemen, already tortured with debt, a heavy burden of imperial taxation; and there was the irritant of existing central government interfering with men's lives; there was the tyranny of the lawyers and their charges. (emphasis mine)

To all this Islam came as a vast relief and a solution of strain. The slave who admitted that Mohammed was the prophet of God and that the new teaching had, therefore, divine authority, ceased to be a slave. The slave who adopted Islam was henceforward free. The debtor who "accepted"
was rid of his debts. Usury was forbidden. The small farmer was relieved not only of his debts but of his crushing taxation. Above all, justice could be had without buying it from lawyers. . . . All this in theory. The practice was not nearly so complete. Many a convert remained a debtor,
many were still slaves. But wherever Islam conquered there was a new spirit of freedom and relaxation.

It was the combination of all these things, the attractive simplicity of the doctrine, the sweeping away of clerical and imperial discipline, the huge immediate practical advantage of freedom for the slave and riddance of anxiety for the debtor, the crowning advantage of free justice under few and simple new laws easily understood_that formed the driving force behind the astonishing Mohammedan social victory. The
courts were everywhere accessible to all without payment and giving verdicts which all could understand. The Mohammedan movement was essentially a "Reformation," and we can discover numerous affinities between Islam and the Protestant Reformers_on Images, on the Mass, on Celibacy, etc.

The marvel seems to be, not so much that the new emancipation swept over men much as we might imagine Communism to sweep over our industrial world today, but that there should still have remained, as there remained for generations, a prolonged and stubborn resistance to Mohammedanism.

There you have, I think, the nature of Islam and of its first original blaze of victory.