It is the negation of the virtues of heaven, just as Satan is the negation of God.
This city of earth is a spiritual (or "Platonic") reality, but not a physical reality.
It is fundamentally incorrect to presume that Augustine simply equated the "city of earth" with the actual physical world and human society.
The physical world and human society, which he described as "the State," is neither the city of earth nor the city of heaven.
The State hovers between the two spiritual cities, and will tend to slide towards the "city of earth" unless people deliberately and consciously struggle to achieve the goals of goodness, order, and peace which accompany the "city of heaven."
The "city of heaven" can never be perfectly achieved on this earth. There can never be a heaven on earth, but a relative goodness, order, and peace can be achieved which would mirror and imitate the absolute goodness, order, and peace in heaven.
Certainly, Augustine never suggested that on earth the church equated with the "city of heaven" and the State with the "city of earth."
Even so, the argument of Augustine and his imagery of the "two cities" was commonly - conveniently?! - read and understood incorrectly in the Middle Ages as a justification for papal claims to temporal sovereignty.
To the contrary, he regarded the Church as a separate assembly of travellers whose eyes are fixed on the "city of heaven" and the next life while enduring as well as possible the imperfections of this world.
Augustine was not greatly interested in the study of politics
or political theory
; however, when interpreted most strictly, Augustine would in this way appear to be in favour of the complete separation of Church and State.
(Continued on the next page.)