"Why Medieval Logic Matters"

The three greatest centuries for logic were the 4th BC, the 14th AD, and the 19th AD. The philosopher interviewed here suggests that this order is not merely temporal but is also the order of importance, such that if we were to speak of the "two greatest centuries for logic" the 19th century would drop out.

Want to know why? Enjoy wrestling with a thorny paradox or two?

What truly deserves the title ‘paradox’ is the Knower paradox. Consider the proposition, ‘You don’t know this proposition’—call it U, say. Suppose you know U. Then U is true (one can only know truths), so you don’t know U. Contradiction, so (by reductio ad absurdum) you don’t know U. But that is what U says. So U is true, and moreover, you’ve just proved it’s true, so you know U. That really is a contradiction—we can prove both that you know U and that you don’t, that is, that U is both true and false. But surely that’s impossible!

Consider the solutions. Do you like the 14th century solution better than the contemporary ones?