When speaking of the City of God, we have to begin with the unfallen angels. This is because they have always been its citizens, unlike the demons and men who were citizens and fell, and unlike the Christians who were not citizens but have now been adopted.
The Bible is unclear as to when angels were created, but it was probably very early in Genesis (as in, Genesis 1:1 with the angels being included in the "light"):
For, 'the true light'... [John 1:9] illumines every pure angel that he may be light not in himself but in God. And, once an angel rejects this Light, he becomes impure. Thus, all those who are called unclean spirits are no longer light in the Lord but darkness in themselves, being deprived of a participation in His eternal light. For, evil has no positive nature; what we call evil is merely the lack of something that is good.Here Augustine introduces the greatest definition of evil a Christian theologian has been able to come up with so far (one repeated by every theologian worth his salt since then).
The "good" which defines the City of God is none other than God Himself existing in His Triune glory. The Trinity alone can be said to both have the Good and be the Good. That is, God at the same time possesses Goodness as an inherent feature of His Trinitarian character and is Good by definition.
Mankind (and the angels), on the other hand, can be made good (by God) but lose possession of that goodness in rebellion.
So too with Life and with Wisdom. "He has life and is the very life He has," and "in this Wisdom there is an infinite and inexhaustible treasury of intelligible realities containing all the invisible and unchangeable ideas of all the visible and changeable existences which were made by this Wisdom."
From God's very nature flows Goodness and Life and Wisdom to the creation which He shaped, and therefore that creation both is good, living, and wise, and possesses goodness, life, and wisdom (until it rebels).