Monotheism and Dualism
Part Two of Prof Harari's lectures on the history of religion is devoted to monotheism and dualism. The first monotheistic religion that we know about, he says, was invented in Egypt by the Pharoah Akenaton. This practice did not survive him. The general strategy of going to monotheism is the promotion of one of the gods to supreme status and suppression of all the others. The first monotheistic gods were local or tribal gods, like the god of the Jews. One obscure Jewish sect invented a new idea - if our god is the god of everything, maybe he is the god of everybody too.
The impact of this globalization of the God's interest was revolutionary. Soon this obscure sect of an obscure religion (Christianity) had swept the Roman Empire. Under the influence of Paul of Tarsus, it became a missionary religion. The second big monotheist religion, Islam, followed the same blueprint sweeping from an obscure sect in a global backwater from ocean to ocean. Today, most of the world follows one of these monotheist religions, with only South and East Asia as major exceptions.
Monotheism has a big problem, from an explanatory standpoint - the problem of evil. If God is all-powerful, and good, how do we explain evil? One answer to that is dualism - dividing the power between a good god and an evil one. Dualist religions flourished for a while, but were largely exterminated by the monotheists. In the process of eliminating dualism, big chunks of it were incorporated into the monotheistic religions. Thus we have God and Satan, Satan being a junior but still powerful god opposed to the God.
Polytheism proved as difficult to eliminate as dualism. One god is really not enough to look after all the interests of society. Consequently, a whole pantheon of junior gods, or Saints, were admitted. These Saints could tend to special interests - every Christian nation had a patron Saint, for example. Occupations got their Saints too - Saint Matthew, for example, is the patron Saint of tax collectors. In many cases, the Saints were merely repurposed gods from the old pagan pantheon - the popular goddess Brigid, of Ireland, got converted and became Saint Brigette.
One bad consequence of the incorporation of dualistic elements was the notion that God might appreciate human help in dealing with Satan. Of course it's ridiculous to imagine that an omnipotent God is going to need any help in deciding whom should, for example, occupy Jerusalem. Once you admit Satan, it almost makes sense that he might want some help that might tip the balance - and thus we get crusades.