In regards to the role of the church in secular affairs and secular authorities assuming dominion over ecclesiastical appointments during the High Middle Ages, I was already well aware of the significance of the Investiture Controversy. However, in Medieval Political Theory - A Reader: The Quest for the Body Politic, ed. Cary J. Nederman and Kate L. Forhan (Routledge: London & New York, 1993), a fascinating argument is put forth that suggests this event had serious implications for the rise and development of secularism. Here's an excerpt I will take from pp 15-16 (the bold text is my own doing):
Although the British now have a Goddess-Queen in their constitutional monarch Elizabeth II, supreme governor of the Church of England, as an American I can completely identify with this strict division between church and state, as enshrined in our badass US Constitution, ratified in 1788 and put into force in 1789.The secular character of many Church offices became controversial over the course of the eleventh century, when the Church experienced several waves of reforms. The culmination of this reforming urge came with the elevation of Pope Gregory VII (1073-85), who prohibited the appointment of clerical officials by temporal rulers (so-called lay investiture) in a 1075 decree. Gregory's prohibition was unequivocal...
This proclamation sparked off a conflict with the Roman Emperor Henry IV (1056-1106), who viewed the Gregorian position as a direct affront to his customary rights as a temporal ruler and to his ability to maintain political order within German society. In the course of the ensuing controversy, Gregory and Henry each asserted the ultimate authority of his respective office over the other, to the extent that they both issued proclamations of deposition against one another.
The emergence of this conflict was significant for the development of medieval political thought in several ways...In sum the Investiture Controversy provided an early opportunity for thinkers to begin to speculate about the nature and origins of government and rulership, and thus created an intellectual climate within which secular political thought might emerge.
The eventual resolution of the conflict was no less important for the evolution of medieval political ideas. The contest between papal and temporal authorities persisted into the early twelfth century, spreading to other Western European countries. Although it may be too simplistic to say that the views of the Gregorian reformers were victorious, the Church did succeed in establishing its independence from secular control in a manner analogous to that originally proposed by Gregory VII. In 1107 King Henry I of England renounced his rights of investiture, although on condition that ecclesiastical magnates continue to perform feudal homage to the Crown. Similar terms were accepted by the German Emperor Henry V (1106-1125) in 1122, after another prolonged period of strife between the imperial and papal powers. The effect of this resolution was more profound than it might appear. For thousands of years, the pre-modern societies of Rome, Egypt, China, Mexico, Peru and Japan, for example, were essentially theocratic, that is ruled by a God-King or by a priestly caste. The distinctively different character of Western and modern politics developed in part through the separation of secular from religious power. For in freeing the offices of the Church from the direct control of the princes, the secular rulers had also succeeded in liberating themselves from the immediate responsibility for religious and ecclesiastical affairs. Likewise, religious leaders liberated themselves from the burden of secular responsibilities. Henceforth, the world of medieval politics was understood to be composed of two mutually independent coordinate powers: the regnum (secular kingdom) and the sacerdotium (spiritual realm). Each of these spheres enjoyed its own distinct concerns and interests which, while somewhat overlapping, were fundamentally separate. This lent to temporal politics a measure of autonomy which it had not enjoyed previously during the Middle Ages. It also created a political climate within which theoretical speculation about uniquely human, earthly public affairs could commence. Thus, the resolution of the Investiture Controversy in the early twelfth century simultaneously heralded the dawning of a more strictly secular tradition within medieval political theory.
Seriously, though, for me this passage raises so many questions!
For starters, I wonder if some will take issue with the insistence that pre-modern "Rome, Egypt, China, Mexico, Peru and Japan" were all "essentially theocratic" with God-Kings at the helm. For Rome you could argue that this is alluding to the elected office of pontifex maximus, as well as the later emperors who claimed divine status while living on earth (or had such titles bestowed posthumously). This was started even with the very first emperor, Augustus. For Egypt this claim doesn't need much of an argument behind it. The pharaohs thought themselves to be the god Horus incarnate and sons of the sun god Ra. For China, ever since the Qin dynasty the emperors were titled not only as huángdì, a combination of two words referring back to the sovereign deity figures of Chinese mythology, but also as tianzi, or the Son of Heaven, serving as theocratic monarchs believed to be at the center of the cosmos. The Japanese emperors were viewed in similar fashion as the Chinese sovereigns. As for Mexico and Peru, this is an obvious allusion to the Mayans, Aztecs, Incas, etc. and their rulers. For instance, the Sapa Inca, rulers of the Inca Empire, claimed Manco Cápac as their ancestor, an earthly ruler who was considered the son of the sun god Inti. The Aztec emperor, or Tlatoani, also served as the high priest of their polytheistic religion.
If, hypothetically speaking, this event hadn't happened and secular and ecclesiastic authorities had remained entwined as they were in the Early Middle Ages, would Western Europe look more like, say, the Islamic Republic of Iran today? By that I mean the lines between church and state would be absolutely blurred, not that Europe would be Islamic.
I'd like to know a much more thorough history about the effects of this division of church and state, up until at least the Early Modern Period, in which I am knowledgeable about the most obvious examples at least. How did this formal separation decided at the Concordat of Worms affect, say, the thinking of Denis Diderot, Voltaire, Baruch Spinoza, James Madison, Thomas Jefferson, and Thomas Paine? Did these Enlightenment-era philosophers and political theorists realize its importance at all?
Also, in fleshing out the First Amendment to the US Constitution that guarantees separation of church and state by not establishing a state religion, did the founding fathers refer back to this event and were they fully aware of its importance in setting precedent? From what I recall, the founders frequently cited the examples of successes and failures in ancient Greece and Rome as those to follow or avoid, but what of medieval society and the lessons it also had to provide? Obviously the English Bill of Rights established in 1689 had the greatest impact on the drafting of the US Bill of Rights, the first ten amendments to the US Constitution. However, given the context of the English Bill of Rights as largely the product of the Glorious Revolution of 1688 and Protestant backlash against Catholic authority personified by James II of England (the last Catholic monarch ruling England, Scotland, and Ireland), could it be said that the founders drafting the US Constitution looked elsewhere for inspiration on this topic?
There is, of course, the worthy discussion we could always have about the potential reversion of this separation by those who would have it so: