Newton is not a classical author. "Classics" basically refers to philosophy, theology, literature and history from 600BC to 600AD. Humanities in Greece and Rome.
Mortimer Adler and Charles Van Doren were, by the way, strong supporters of the reader conversing, even arguing, with the author. I don't the Sanger is on the same page with them, and I don't believe they would agree with his essay.
OK, yes--if, for instance, you go to get a degree in "Classics", you are studying things that were written in ancient Greek and Latin. That's not to say that contemporary philosophers, theologians, historians, and students of literature restrict themselves to that era, though, or that that era is particularly important to them.
