One of my Ph.D classes at Northwestern University was with philosopher and Greek scholar Reginald E. Allen. I don't think I have ever been taught by someone more brilliant.
Arguably, Allen is the greatest Plato scholar of our time. His translations of Plato's dialogues have replaced the Loeb translations.
My class with Allen was on Aristotle's Metaphysics. I remember there being about 7 or 8 of us doctoral students. Allen would usually arrive a bit late, sometimes with the odor of a sandwich on his breath that slowly filled the room. Often, he did not even bring a copy of the Metaphysics with him. That's because he knew the entire thing in Greek!
Ir was not unusual, at times, to see another Northwestern professor sitting in on Allen's lectures, just wanting to hear this Greek philosophy genius explain, deeply, the text. For example, one day sitting next to me around the table in the library-like classroom was the philosopher E.M. Curley, the great Spinoza - Descartes scholar.
One of Allen's favorite texts to interpret Aristotle, which I bought, was Joseph Owens's The Doctrine of Being in the Aristotelian Metaphysics. Allen especially pointed to Owens's idea of "pros hen equivocity" and an intepretive key to understanding Aristotle.
A final note. I once went to Allen's office to ask him a question. He was sitting at his desk reading the Gospel of John. I asked him why he was reading it, and he said it was a good example of Platonic philosophy affecting Christology. I told Allen that I was reading Edward Schillebeeckx's two books on Jesus and Christ. I told him that Schillebeeckx, like many others, dated John's Gospel after the fall of Jerusalem in 70 AD, putting it usually around 90 AD. I asked him where he would date the Gospel of John. He told me he would date it before 70 AD. I asked, how can you do that? I will never forget his response. He looked at me and said, "Don't you believe in prophecy?"