Life in Eden was perfect, as in without sickness or sin or defect of any kind, but only so long as man lived according to God's will. Clearly, "lust" would have no place here, while parenthood certainly would. We can even (limitedly) understand something of how childbirth might not have been painful--but even if we can't it doesn't negate the truth of a perfect pre-fall life. We just can't confirm this by experience:
What, in any case, is certain is this, that God Almighty the ultimate and supremely good Creator and Ruler of all living creatures, the Giver of grace and glory to all good wills, and the God who abandons bad wills to the doom they deserve, was not without His own definite plan of populating the City of God with that fixed number of saints which His divine wisdom had ordained, even though the City had to be filled with citizens chosen from the ranks of a fallen human race.Now that we all fallen, grace and grace alone is the only way into this City. And this not because of any good in us--"for, no one can help but acknowledge how gratuitous and undeserved is the grace which delivers him when he sees so clearly the contrast between his privileged, personal immunity and the fate of the penalized community whose punishment he was justly condemned to share."
So why did God create mankind, knowing that we would sin? Because "both in them and by means of them He could reveal how much was deserved by their guilt and condoned by His grace." And also, Augustine adds, because nothing God creates can be destroyed by sin anyway.
God, therefore, is sovereign over all things and turns but good and bad to His own good ends. "hence, there was no reason why God should not make a good use even of the bad angel who was so doomed to obduracy." Both good and bad alike are dependent on God, the good for strength and endurance, and the bad for existence and (in the case of God's people) forgiveness. To be sure, God could have forcibly stopped the fall. Yet, He chose not to do so and instead left it up to the creature. "In this way, God could show both the immense evil that flows from the creature's pride and also the even greater good that comes from His grace."
So we have the two cities. The city of man "flowered from a selfish love which dared to despise even God;" while the City of God "is rooted in a love of God that is ready to trample on self." The City of God rests on God alone, while the city of man tries to rest on itself. Consequently, lust and domination mark out the city of man, while the City of God is marked by charity and obedience. Even when the wise philosophers of the city of man know true things about God, they turn them to wicked and self-serving purposes. God's people, on the contrary, find their wisdom through "piety which worships the true God as He should be worshiped and has as its goal that reward of all holiness... which is 'that God may be all in all.'"