He is a philosopher and Christian apologist. He was originally Calvinist and later converted to Catholic. He seems an expert on Socrates and wrote many books on Socrates. I came to know him through the book, Handbook of Christian Apologetic, and Christianity for Modern Pagan, which is about Blaise Pascal. In this particular video, he talks about Five proofs of God’s existence by Thomas Aquinas, from Summa Theologica.
I read this from other books, but could not quite get it. They seem all the same kind of argument, but Peter Kreeft explans well in this video and help me to understand better. He also wrote a book about Summa of Summa Theologica, which gave me an introduction to the original text.
From his website, http://www.peterkreeft.com, I found a very good writing on the problem of suffering, http://www.peterkreeft.com/topics/suffering.htm. There are a lot of approaches to this issues, intellectual, emotional and pastoral. But his approach is unique though it is close to pastoral. The answer for this problem should be about someone, not something, because the problem itself is not just intellectual, but emotional and personal problem. He also has many good apologetic responds.