This is a thought-provoking essay. Excerpts with a bit of commentary:
Belloc’s thesis is that Islam began as a Christian heresy which retained the Jewish side of the faith, the Oneness and Omnipotence of God, but denied all the Christian aspects -- the Incarnation, the divinity of Christ, who, as a result, became just a prophet. The denial of the church, the priesthood, and the sacraments followed. Islam succeeded because, in its own terms, it was a simple religion. It was easy to understand and follow its few doctrinal and devotional points.
Question: Given that Islam is much closer to Judaism than is Christianity, what explains the murderous ferocity of the Muslim hatred for Jews? One part of the explanation must be in terms of envy. Muslims feel profoundly diminished in their sense of worth by Jewish success and well-being. The Jews have made outstanding contributions to culture out of all proportion to their sparse numbers, whereas the hordes of Muslims have languished for the last four hundred years in backwardness and negativity. What else but envy could motivate the wild cries for the extermination of Jews and the destruction of Israel? Ahmadinejad, you will have noticed, is not a Palestinian, but an Iranian. When non-Palestinian Muslims call for the elimination of Israel, and prepare for decades of suicidal jihad, their 'beef' cannot be a relatively minor land dispute between Israelis and Palestinian Arabs.
Unlike Stanley Jaki, Belloc did not think that there was something in Islamic theology that militated against Islam’s ever becoming a major industrial or military-technological power by itself. (133). The fact that it never accomplished this transformation was for Belloc merely an accident, whereas for Jaki it was rooted in the relation of an absolute notion of divine will to its consequent denial of stable secondary causes. Jaki sees much of the rage in modern Islam to be due to its failure or inability to modernize itself by its own powers.6 Most of the weapons and equipment found in Muslim states are still foreign made, usually inferior, and paid for with oil money.
Islam apparently takes an occasionalist view of divine omnipotence. God is all-powerful not just in the sense that he has the power to do all, but in the sense that he exercises all the power that gets exercised. Thus secondary causes -- so-called to distinguish them from the causa prima -- are not causes at all, strictly speaking, but mere occasions for the exercise of divine causality, the only causality there is. If so, then everything is up to God, and nothing is up to secondary 'causes' including ourselves. When I lived in Turkey, I was struck by the prevalence of the belief in kismet, or fate. It is reflected in driving habits. Turks are arguably the worst drivers in the world. It is as if they don't believe that what happens on the road is largely up to them: kismet rules. When your number's up, it's up, and it doesn't matter what you do.
The very existence of Christianity is a blasphemy in Muslim terms if we insist on the truth of the Incarnation, that God became man.
In the eyes of Islam, Christianity is a form of idolatry: a mere man is identified with God. Schall quotes Belloc:
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. Its 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 misuse, of the Christian thing (76-77). Though it is not often attended to, saying Mass itself is forbidden in Saudi Arabia, even in private, and, even when permitted in other lands, it is restricted and constantly hemmed in by various formal and informal practices. Freedom of religion is not a concept that rises naturally in Muslim theory but it is a Western idea, even largely a modern Western idea. In Islam, the very practice of freedom of religion is thought to be a species of not giving submission to Allah, even where some non-Muslim churches are permitted. Belloc thought that the Mohammedan temper was not tolerant. It was, on the contrary, fanatical and bloodthirsty. It felt no respect for, nor even curiosity about, those from whom it differed. It was absurdly vain of itself, regarding with contempt the high Christian culture about it. It still so regards it even today (90). The practical compromise in this situation was to allow the Christians to remain but within very confined areas and occupations. They had to pay a tribute. Many were gradually absorbed into Islam (91).