In my second logic course I start with some very basic set theory.  You forget just how confusing symbols can be to students who aren’t used to them. But then you also appreciate how useful they are when you try to explain in “plain English” what they mean. Even something as simple as a proof of X ∩ Y ⊆ Y ∩ X is hard. I tried to write a proof of it in the Up-Goer Five text editor. It’s up top. What do you think?