I am a huge fan of @ProfPaulPoast and I'm in awe of his threads about teaching IR. But I rise to offer a respectful dissent to this tweet: https://twitter.com/ProfPaulPoast/status/1288252100808454145
To be fair, Paul has a longer and thoughtful threa on the subject here: https://twitter.com/ProfPaulPoast/status/1288440923752484867
Here's my reaction:

I've been teaching a course on realism for several years. It uses a lot of "classic" texts: Thucydides, Kautilya, Machiavelli, Hobbes,Schmitt, etc. There are plenty of "modern" realists too (Carr, Spykman, Niebuhr, Morgenthau, Waltz, JJM etc. ), along w/some important critics.

The older texts are useful in part because they are hard to read and understand. Students have to slow down and think hard about the assumptions and causal claims these writers are making. This is good training in how to dissect the logic of an argument and find its flaws.

Furthermore, when I go back to certain classics, I find insights I had missed and sometimes I change my mind about them. I thought Morgenthau's SCIENTIFIC MAN VS. POWER POLITICS was terrible when I first read it, and only realized its important insights many years later.

Second, reading old texts invites discussion about how much of an argument or theory is universal and how much is context-specific. Thucydides claims to offer us "a possession for all time," but did he succeed? Or are his arguments limited to his own time and place?

Moreover, given that people often invoke these famous writers to justify policies today, reading them carefully can help us decide if they are being invoked accurately or not. See here, for example: https://www.tandfonline.com/doi/abs/10.1080/09636412.2018.1508634?journalCode=fsst20

Similarly, Pericles' famous funeral oration can be discussed in ways that echo current concerns: as an expression of Athenian "exceptionalism," a moral justification for imperialism, or a shameless bit of "stay the course" rhetoric designed to bolster support for a war.

Furthermore, using classic texts inevitably invites interesting discussions of gender, because most/all of the writers in the "canon" are male. How would the history of IR thought be different if female thinkers had played a more active part in previous centuries?

In this way, reading old texts also introduces students to the sociology of knowledge. How does Machiavelli go from obscurity after his death to a prominent position in Western thought today? Why are Morgenthau and Waltz more famous than Herz, Spykman, or Gilpin, etc.?

Lastly, when one discovers that a lot of earlier thinkers had figured out some of the insights that we like to think are original today, it helps keep us all humble. That's a useful contribution right there.

Very importantly, Paul and I agree that there are lots of different ways to teach our field and that individual faculty should follow their own instincts. I have no doubt that Paul's classes are terrific. But it would be fascinating to see what he could do with Thucydides!