“Saint Augustine proliferated central theological and political doctrines of the Church, following Saint Paul closely. History is the scene of the struggle between the Heavenly and Earthly Cities, but only God before the Last Judgment knows the membership rolls. Human nature is so sinful (rebellious and corrupt) that only those who have received grace, i.e., have been chosen by God to love Him, can be saved for eternal life. This theory caused a lot of trouble for the medieval church, which by and large abandoned it. It was revived much later by Martin Luther."By the early fifth century, at a series of church councils, the Christians had hammered out a compromise theory of the Trinity -- God the Father, the Son, and the Holy Spirit (Church) -- more or less of one substance but with three personalities. Those who would not accept this compromise were branded as heretics and sooner or later persecuted by the imperial state.”