Spiritual insight is the universal instinct that quietly informs individual souls about how to behave, but it is local politics that uses these vague understandings to create laws that make them applicable to large numbers of people. This is how religious doctrines are created. Unfortunately, as the territory enlarges and the population becomes more diverse, so do the doctrinal and political differences between various groups of believers. This leads to the establishment of competing religious sects.
Because of the tenacious hold religious beliefs have on their believers, religious strife between the sects (or competing religions) can lead to serious clashes and even to wars. However, the VAST majority of historical wars were not about religious differences, but about political and economic differences. Religion was just a way to organize these differences, and a good excuse for claiming that God was on your side!
History shows us that secular governments led by kings always take advantage of the natural social cohesion established by the prevailing religion to make war and increase their own power and wealth.
Note: the term “secular” is defined as attitudes and activities that have no religious or spiritual basis. It is, in fact ,the opposite of religion.
This was the case with the Catholic Church in Europe prior to the Protestant Reformation. Ever since the time of Constantine, the Christian church had been heavily intertwined with secular governments. The holy Roman Emperor ruled with the divine right of kings, and the secular government essentially merged with the church. This had immense benefits for both institutions, but it had serious detrimental effects on the church, which assumed more and more secular baggage which it promoted as religious doctrine.
In Catholicism, these doctrines included the selling of indulgences which would allow the wealthy to buy their way into heaven. This corrupt “divine law” sparked a revolt called the Protestant reformation, which in turn sparked a counter-reformation within the Catholic Church. Thus began the slow process of routing out corrupt political practices and some of the ancient and now useless dogmas within Catholicism. The Counter Reformation in turn affected the Protestants and this tended to liberalize the secular governments that were aligned with them.
As the dogmas within all the religious sects became more modernized and liberal, the secular governments found it easier to keep the peace between competing sects, and nations became more coherent. It also became easier to form alliances between different nations because their populations, by and large, believed in the same God.
In the main, the cooperation of religious and secular governing bodies worked spectacularly well. Religions have the advantage that their core of spiritual belief allows people to gauge the justice of the laws that the secular bodies wish to enforce. If people saw that a secular law was morally unjust, it was hard for the authorities to make them obey. Thus, the religious institutions could exercise some control over the secular governments, while the secular governments retained the advantage of force of arms and could keep the peace between the sects. This mutual restraint forced people who were in disagreement over religious matters to live side by side, and eventually the sects began to adopt more tolerant attitudes toward each other.
Much of the strife in the Muslim world can be attributed to the tenacious belief of the vast majority of the population in the tenants of the Koran (Sharia), combined with the many schisms brought about by doctrinal differences between sects. This, plus the fact that Islam has never had a reformation which might have allowed secular laws to operate alongside religious law has produced centuries of sectarian strife. In general, peace must be maintained by a dictator who operates as the head of the both the militarily and religiously dominant sect.