Thomas Aquinas wrote the Summa Theologiae as a textbook for beginners in theology. Yet its full comprehension is beyond the grasp of most PhDs in philosophy today. When a beginner’s manual from the 13th century exceeds the grasp of our highest credentialed experts, we should think seriously about the kind of intellectual regression this represents.

It's not just Aquinas. Read the major philosophers and jurists of any classical tradition, then read their modern counterparts. The difference in erudition and range is striking.