Augustine later stated that it was this book that had set him on his own spiritual quest to find God, and led to his conversion.
This early Christian philosophy of Augustine was largely his rewriting in a Christian context ideas taken from Plato.
The main change that Christian principles brought was a moderation of the Stoicism and of the theory of justice of the Roman world, and an emphasis on the role of the state in applying mercy as a moral example.
The comment that "Augustine baptised Plato" is too simplistic. Certainly, Augustine took much from Plato and from Neo-Platonism and selectively used those thoughts therein that aided him more effectively to explain and to communicate Christianity.
The Oxford History of Western Philosophy summarizes the tremendous influence of Augustine on Western intellectual history as follows:
It is arguable that Augustine is the most influential philosopher who ever lived. His authority has been felt much more broadly, and for a much longer time, than Aristotle's, whose role in the Middle Ages was comparatively minor until rather late.
As for Plato, for a long time much of his influence was felt mainly through the writings of Augustine.
For more than a millennium after his death, Augustine was an authority who simply had to be accommodated. He shaped medieval thought as no one else did. Moreover, his influence did not end in the Middle Ages.
Throughout the Reformation, appeals to the authority of Augustine were common place on all sides. His theory of illumination lives on in Malebrache and in the "light of nature" of Rene Descartes.
His approach to the problem of evil and to human free will is still widely held today. His force was and is still felt not just in philosophy but also in theology, popular religion, and political thought. (Anthony Kenny, ed. The Oxford History of Western Philosophy (Oxford: Oxford University, 1994), pages 57-58.
Link
The Mark of Augustine on Philosophy - By Eugene Portalie in the first edition of the Catholic Encyclopedia. Not easy to read.
