This opus by Pirenne has largely stood the test of time and is a must read for any who wish to understand the turbulent, violent, complicated civilising mission and history of Christian Europe.  Some elements have been overturned or recalibrated including his assertion that the Musulman invasion completely destroyed all Mediterranean and commerce by the late 7^th century (not entirely true, but his point is still valid).  Pirenne is not a Christian apologist, being quite critical of both the religion and its ecclesiastical culture and societal development, whilst maintaining a deep regard for its importance, civilisational mission and its defence of Europe against the Musulman invasions.  In summary it is clear, no Catholic Church, no European civilisation.  All would have descended back into pagan barbarism.  Some important excerpts from Pirenne, on this topic below.

The Musulman invasion(s) and Jihad

Musulmans appeared as the propagandists of a new faith, an exclusive and intolerant faith to which all had to submit. Religion, wherever they ruled, was the basis of political society; or rather, the religious organization and the political organization were for them identical; Church and State forming a single unity. The infidels could continue the practice of their cult only as simple subjects, deprived of all rights whatsoever. Everything was transformed, from top to bottom, in accordance with the principles of the Koran.

Koranic theology was society.  The Christian Church promoted the opposite – the absolute division of Church and State.

[Musulmans] can boast of little that is original. The conquered peoples were all more refined than their nomad conquerors, and the latter borrowed from them in a wholesale fashion. The Arabs translated the works of their scholars and philosophers, drew inspiration from their art, and adopted their agricultural, commercial and industrial methods. The extent and diversity of the countries and the nations upon which they imposed their rule subjected them to a quantity of influences, which blended together, giving the Musulman civilization an aspect of great variety, but little depth, of these influences, that of Hellenism rivalled that of Persia.

The Musulman Jihad, attacked, conquered, and squatted on far richer civilisations.  The driving impetus and galvanising feature of the Musulman Jihad was precisely the allure of richer states. 

Aristotle was the master of the Arab philosophers, who added nothing essential to his philosophy. On the whole, in the intellectual domain, the Musulman civilization did not greatly influence the European peoples. The explanation is simple: there was much in it that was artificial, and the sources upon which it drew most freely were, for the most part, European sources.

Musulmans did not build on ancient wisdom.  Nestorians and other Christians had translated their works for the new masters, but no discernible improvements or additions were made by the Musulmans.  It was static learning.

From the 7^th to the 11^th century Islam was incontestably the master of the Mediterranean. The ports which the Arabs constructed—Cairo, which succeeded to Alexandria, Tunis, and Kairouan—were the étapes of a commerce which circulated from the Straits of Gibraltar to the Indian Ocean, through the Egyptian ports, which were in communication with the Red Sea, and the Syrian ports, which gave access to the caravan route to Baghdad and the Persian Gulf. The navigation of the Christian peoples was restricted to a timid coastwise trade along the shores of the Adriatic and southern Italy, and among the islands of the Archipelago.

The Musulmans cut off the Mediterranean and the Christian civilisation of North Africa and the Levant was conquered, splitting West Christendom from Byzantine Eastern Christendom.  Trade, culture, wealth, and technology were all negatively impacted.

For centuries Europe had gravitated about the Mediterranean. It was by means of the Mediterranean that civilization had extended itself; by means of the Mediterranean the various parts of the civilized world had communicated one with another. On all its shores social life was the same in its fundamental characteristics; religion was the same; manners and customs and ideas were the same, or very nearly so. The Germanic invasion had not changed the situation in any essential respect. In spite of all that had happened, we may say that in the middle of the 7th century Europe still constituted, as in the time of the Roman Empire, a Mediterranean unity.

The ’Dark Ages’ or the reduction in traffic, commerce, wealth and de-urbanisation, only occurred after the Musulman takeover of the Mediterranean and the dismembering of its Christian unity.  This historical fact is still relevant today and still the reason, why there are conflicts in North Africa and the Middle East. 

The intercourse between the West and the East, which had hitherto been carried on by means of this sea, was interrupted. The East and the West were suddenly separated. The community in which they had lived so long was destroyed for centuries to come, and even to-day Europe is still suffering from the consequences of its destruction.

The destruction of Christian-Mediterranean civilisation was an epochal event, still resounding and reverberating even today. 

The Mediterranean by which it had hitherto kept in touch with civilization was closed to it. This, perhaps, was the most important result, as regards the history of the world, of the expansion of Islam.  For the Christianity of the West, when its traditional lines of communication were cut, became a world apart, able to count only on itself, and in respect of its further development it was thrown upon its own resources. Driven off the Mediterranean, it turned to the still barbarous regions beyond the Rhine…

Post 800 A.D. Europe looked to the North, the East, and to the Atlantic to rebuild itself and repair civilisation.  The littoral around the Mediterranean was either conquered by Musulmans or prey to savage piracy and slave trading.  Christian Europe retreated to the North and East.  Its large urban centres based around the Mediterranean became depopulated.  Taxes and trade were reduced.  Government was impaired.

In the second half of the 7th century all trade ceased on the shores of the Western Mediterranean. Marseilles, deprived of her ships, was dying of asphyxia, and in less than half a century all the cities in the south of France had lapsed into a state of utter decadence. Trade, no longer fed by sea-borne traffic, came to a standstill throughout the country: the middle class disappeared: there were no longer merchants by profession; there was no circulation of goods, and as a natural result the market dues no longer fed the royal treasury, which was henceforth unable to defray the expenses of government. Henceforth the landed aristocracy represented the only social force. The king was ruined, but the aristocracy, with its land, possessed wealth and authority. It only remained for it to seize political power.

The Church as saviour

Nevertheless, decadent though it was, the Church was the great civilizing force of the period; indeed, we may say the only civilizing force. It was through the Church that the Roman tradition was perpetuated; it was the Church that prevented Europe from relapsing into barbarism.

The Church swept up the pagan Roman empire and its infrastructure, learning, engineering, urban planning, literature, and ideals and combined them with Christianity, Christian philosophy and Christian science and culture.  It fought innumerable wars to save Christian Europe from Koranic domination.  Literate Church clerics kept learning alive, even as papyrus disappeared thanks to the Musulman invasion.  Social cohesion including hospitals, schools, hospices, roads, taxes and infrastructure, were dealt with, albeit in a haphazard and often inefficient way.  But society was restored, and after 800 A.D. growth and wealth creation become apparent as the foci of Roman Catholic civilisation shifts north and east looking to the Atlantic and Baltic and eventually the horn of Africa and beyond as it fought, defeated and constrained the Musulman Jihad. 

The main point made by Pirenne 100 years ago is still valid today.  The Musulman Jihad forever transformed the Mediterranean and accelerated the development of a distinctly superior European Christian civilisation.