Augustinian Demonology and Angelology in shaping the Concept of the City of God

Augustine creates his City of God according to ChristianDemonology and Angelology. In his opinion, God has bestowed the good nature upon all the angels but what makes some of them go astray is their negligence of God's love. In fact, arrogance is the first step in creating a gap between the angels, which divides them into two categories holy angels and evildoers, so they form two cities. This Augustine's perspective raises this question: why did the angels fall? Augustine himself relying on the teachings of the Bible answer that autonomous and self-initiated sin of pride caused the angles to divert from God's will. Augustine, in this way, arranges and explains one of the most important concepts of Christian theology on the basis of angelology, in such a way that no one has done this before in the Christian theology.