The 'City of God' is a concept that refers to the spiritual and eternal kingdom of God, as opposed to the earthly, temporal 'City of Man.' It is a central idea in Christian philosophy, particularly in the work of Saint Augustine, which explores the distinction between the divine and the worldly. The term 'City of God' connects to the topics of 4.3 Jewish, Christian, and Islamic Philosophy by representing a key theological and philosophical framework within the Christian tradition. It highlights the Christian perspective on the relationship between the spiritual and material realms, and the ultimate purpose and destiny of humanity.