Peter Kreeft:

As the essential comparison in ancient philosophy is between Plato and Aristotle, the essential comparison in medieval philosophy is between Augustine and Aquinas.

It is not so much a contrast doctrinally between a Christian Platonism and a Christian Aristotelianism as a contrast personally between two different sets of remarkable talents and temperaments.

Augustine speaks from the depths, Aquinas from the heights.

Augustine’s insight is into man existential, Aquinas’s is into man essential.

Augustine is the master of metaphor, Aquinas of concepts.

Augustine’s head and heart are in a rich, stormy marriage; Aquinas’s heart and head are in perfect, quiet unity.

Augustine has less practical confidence in human reason than Aquinas does because he knew from experience how wounded and self-deceptive it could be, while Aquinas was born, lived, and died in the light. This gives Augustine a richness and a passion but also a one-sidedness and a straining that contrasts with Aquinas’s ease and balance.

It is the playboy who wanted to do without God and grace, and who experienced the weakness of nature and natural reason, who shows us our own deepest needs, sufferings, and failures. It is the perfected saint who shows us the essential nature of God, ourselves, and our philosophical cosmos as clearly as anyone ever has.

Yet their teaching is essentially the same both in principle and in practice.

The common principle is that grace and faith must precede and perfect nature and reason, but when it does, nature and reason are indeed perfected, not diminished.

The common practice is that both enable our thought to be one with our prayer.

—Peter Kreeft, Socrates’ Children: The 100 Greatest Philosophers, Volume II: Medieval Philosophers (South Bend, IN: St. Augustine’s Press, 2019), 81–82.