The moral history of Christianity (The Elect, predestined for salvation at birth) is derived from the Jewish covenant with God (Chosen people, Jewish nation); the monotheist aspects are derived from Platonic/Orphic elements.  The psychology of Jewish state can be viewed as a purification through collective punishment; hostilities (by others) are sublimated into even greater faith towards virtuous actions. Although the Christians did not adopt such a broad concept (a nation of religion), they did place their elect on pedestals which produced a transitional object (the institution of the church) that circumvented the problem of original sin; descendants of Adam and Eve are all fallen and could only be saved by the grace of God which was predestined (arbitrary). The church, being a non-human, is exempt from such sin and would serve as a conduit/bridge to carry out the authority of God. Such authority was eventually recognized by the state for several reasons: The lack of a Christian nation made man’s direct relation with God the rationale for suffering, which during the declining years of the Roman states, siphoned away much of faith in material to a faith in the spiritual. Man’s soul was not ready the fall of the Godhead (freedom), and so a third object (Church institution) emerged to buffer the regression into the self. Hints of man’s growing subjectivism can be seen in Saint Augustine’s theory of time (memory, present, expectation).  A consequence of such faith in the afterlife is a fear-mongering campaign against eternal hell-fire; those who weren’t baptized (converted) would suffer eternal damnation, a fate much worse than the squalid conditions faced on Earth.

     
The power of the papacy over the state over the coming centuries was aided by efforts of theologians such as Saint Augustine (provided theoretical grounds for the supremacy of the Church) and other figures such as Saint Benedict (monk), Saint Gregory the Great (statesman) for controlling education/teachings (monastic life) and courting both the Emperors of Rome and the Barbarian warlords. Augustine’s City of God juxtaposed punishment in life for eternal punishment in the afterlife, raised virtue in mind over action, and authorized the Church in its own righteous defense of itself (just-war). The Church’s outreach (monastic order), via almsgiving and the education of its own beliefs/practices (miracles, preserved knowledge through dark-ages), converted the masses toward the faith.