Peter Kreeft is a prolific Catholic philosopher and apologist. He has written numerous books on apologetics and introductions to philosophy that I greatly enjoyed. What makes Kreeft’s introductions different is their dialogical format. Plato wrote his philosophy in the forms of dialogues, and Kreeft has followed that tradition. In Kreeft’s case, the dialogues occur between Socrates and a great philosopher (e.g., Descartes, Kant, Hume, Marx, even Jesus, et al.). Reading philosophy is never easy, but Kreeft makes it as enjoyable as it possibly could be. He is a witty writer—reminiscent of G. K. Chesterton and C. S. Lewis. Although I disagree strongly with his Roman Catholicism, I’ve greatly benefited from his defenses of the existence of God and traditional Christian morality (e.g., on abortion, marriage).
Here is a quote from Kreeft on free will, from his book, Summa Philosophica. In rethinking or answering the Calvinist doctrine of “total depravity,” one of the questions involves free will. Do we have one? Defenders of total depravity deny that we do. I think we do. Part of the Biblical evidence for free will is all of God’s moral commands, judgments, evaluations, and rewards. Why do those count as evidence for free will? Kreeft explains:
I answer that (1) If free will does not exist, all moral language becomes meaningless. For it is meaningless to praise, blame, reward, punish, counsel, command, forbid, or exhort an unfree agent such as a machine or a “dumb animal.” When the Coke machine fails to deliver a Coke, we do not accuse it of sin and tell it to go to confession; we kick it.
(2) And since rewarding and punishing are the acts of justice, if free will does not exist, justice itself becomes meaningless. But without justice all higher moral values such as mercy and forgiveness and even love are meaningless. And without love, human life itself is meaningless. Therefore if there is no free will, human life is meaningless” (Summa Philosophica, pp. 113-114).