I think the focus on the distinction between religion and politics is basically wrong. The division between Church and State was a product of the unusual circumstances after the fall of the Western empire and always rejected in Byzantium. In the West it was widely regarded as anomalous and a source of chaos (because it was) and the view that the secular ruler was also by right head of the Church was advocated, among others, by Marsillius of Padua, Dante, Luther, Calvin, Zwingli, and Henry VIII. The main opponents of this were, obviously, the papacy, but not because they believed in a separation either. Rather they maintained that the Pope was lord of all the earth who appointed, and could depose, kings as his deputies. The fact of separation was because neither side won.
Rather, in addition to the accidental fact of institutional disunion, I'd argue that the different trajectories of Christendom and and Dar al-Islam can best be explained by the following factors:
1) Not political doctrine, but Pauline anti-legalism (or perhaps anti-Judaism) created a sphere of religiously indifferent acts, which is roughly coterminous with what we call culture.
2) For 300 years, a sizable proportion of the intellectual classes in Christendom just haven't believed in Christianity. In England, already by 1750 a good quarter of the clergy [!] are some kind of unitarian or even deist. Bolingbroke was more or less openly a heathen, to say nothing of the Whigs. Most of the American founding fathers didn't believe in a small-o orthodox version of Christianity. By the nature of things, the fact that large parts of the elite don't buy into the established religion to various degrees is going to create space for a 'secular' sphere.
For the Church of England, as has been said, God is an optional extra. Nice to know some things never change.
I possibly should have spelled this out more (I was trying to keep the word count down ... an effort that ultimately failed anyway). No State in Christendom was "secular" as we use that term now in politics until the last century, really. But the conceptual existence of "the secular" is there in Christianity in embryo from the beginning - I think you are right to fix on Paul's notion of Law (written on the heart rather than tablets) - and Church and State are present as a duality even in phases where one dominates the other. At the height of the Latin Church's powers in the Middle Ages, there was still a "secular arm".
There is a resemblance between the classical Islamic order and Byzantine Caesaro-Papism, but the parallel is more apparent than real. There was the Byzantine Emperor and the Patriarch, a secular bureaucracy and a hierarchy of metropolitans, bishops, and priests, each with delimited powers, roles in the life of believers, and day-to-day functions. Islam has none of this division and when something akin to it does appear, in the Ottoman Empire in the nineteenth century, it is imported as part of the Westernising reforms
In the sense of the supreme upholder of God's Law and His "shadow on earth", yes. Formally, the terms of the deen were determined by a consensus of the ulema, but by that time the consensus was fixed - the gates of ijtihad had long since closed - and the ulema answered to the Sultan, as became apparent later with the changes on slavery.
Tangentially but I don't think totally unrelatedly: it's notable how absent Turks are among the great theologians in Islam, despite creating the greatest of the Islamic Empires. The Turks were the soldiers and administrators of an Islam that had "set".
One of the few changes from the Ottoman period was more vibesy than strictly theological, and it was contingent: the hardening of the Sunni-Shi'a division. What had been more in the nature of an Arab tribal dispute became an issue comparable to that of Christian "sects" in the hands of the Ottoman Turks and Safavid Iranians - they had to reason their way to understanding the difference and then it was inflamed by their contest for supremacy.
That I cannot say, but complaints about zulm (injustice, tyranny) in a ruler had no impact on the fundamental perception of the world and of identity as an umma with the Caliph at its head following a deen that encompasses obligations beyond private belief, of personal practice and public life (what Christendom would call politics, the law, etc.).
I think the focus on the distinction between religion and politics is basically wrong. The division between Church and State was a product of the unusual circumstances after the fall of the Western empire and always rejected in Byzantium. In the West it was widely regarded as anomalous and a source of chaos (because it was) and the view that the secular ruler was also by right head of the Church was advocated, among others, by Marsillius of Padua, Dante, Luther, Calvin, Zwingli, and Henry VIII. The main opponents of this were, obviously, the papacy, but not because they believed in a separation either. Rather they maintained that the Pope was lord of all the earth who appointed, and could depose, kings as his deputies. The fact of separation was because neither side won.
Rather, in addition to the accidental fact of institutional disunion, I'd argue that the different trajectories of Christendom and and Dar al-Islam can best be explained by the following factors:
1) Not political doctrine, but Pauline anti-legalism (or perhaps anti-Judaism) created a sphere of religiously indifferent acts, which is roughly coterminous with what we call culture.
2) For 300 years, a sizable proportion of the intellectual classes in Christendom just haven't believed in Christianity. In England, already by 1750 a good quarter of the clergy [!] are some kind of unitarian or even deist. Bolingbroke was more or less openly a heathen, to say nothing of the Whigs. Most of the American founding fathers didn't believe in a small-o orthodox version of Christianity. By the nature of things, the fact that large parts of the elite don't buy into the established religion to various degrees is going to create space for a 'secular' sphere.
For the Church of England, as has been said, God is an optional extra. Nice to know some things never change.
I possibly should have spelled this out more (I was trying to keep the word count down ... an effort that ultimately failed anyway). No State in Christendom was "secular" as we use that term now in politics until the last century, really. But the conceptual existence of "the secular" is there in Christianity in embryo from the beginning - I think you are right to fix on Paul's notion of Law (written on the heart rather than tablets) - and Church and State are present as a duality even in phases where one dominates the other. At the height of the Latin Church's powers in the Middle Ages, there was still a "secular arm".
There is a resemblance between the classical Islamic order and Byzantine Caesaro-Papism, but the parallel is more apparent than real. There was the Byzantine Emperor and the Patriarch, a secular bureaucracy and a hierarchy of metropolitans, bishops, and priests, each with delimited powers, roles in the life of believers, and day-to-day functions. Islam has none of this division and when something akin to it does appear, in the Ottoman Empire in the nineteenth century, it is imported as part of the Westernising reforms
I honestly don't know enough about this period, but did Muslims really believe, say, Mehmed III was the supreme religious authority?
In the sense of the supreme upholder of God's Law and His "shadow on earth", yes. Formally, the terms of the deen were determined by a consensus of the ulema, but by that time the consensus was fixed - the gates of ijtihad had long since closed - and the ulema answered to the Sultan, as became apparent later with the changes on slavery.
Tangentially but I don't think totally unrelatedly: it's notable how absent Turks are among the great theologians in Islam, despite creating the greatest of the Islamic Empires. The Turks were the soldiers and administrators of an Islam that had "set".
One of the few changes from the Ottoman period was more vibesy than strictly theological, and it was contingent: the hardening of the Sunni-Shi'a division. What had been more in the nature of an Arab tribal dispute became an issue comparable to that of Christian "sects" in the hands of the Ottoman Turks and Safavid Iranians - they had to reason their way to understanding the difference and then it was inflamed by their contest for supremacy.
But at a more basic level wasn't it well known that Mehmed III was a religiously indifferent and depraved individual?
That I cannot say, but complaints about zulm (injustice, tyranny) in a ruler had no impact on the fundamental perception of the world and of identity as an umma with the Caliph at its head following a deen that encompasses obligations beyond private belief, of personal practice and public life (what Christendom would call politics, the law, etc.).