I'll disagree that it's the use or non-use of notation. I had the great joy of taking an Intro to (mathematical) Logic class with Dr. Richard Vesley (who had K

I'll disagree that it's the use or non-use of notation. I had the great joy of taking an Intro to (mathematical) Logic class with Dr. Richard Vesley (who had Kleene as his Ph.D. advisor!) By that point, I'd had many math classes with instructors all over the bell curve. Dr. Vesley blew them all away. There was notation, but the real clincher was his absolute clarity of communication. He covered a lot of material, but the pace never felt rushed. In fact, it was so calm and so clear it was refreshing, more like meditation by a babbling brook. I wasn't the only one to feel that way -- the whole class seemed to have a similar experience. Related to the story in TFA, a friend of mine with a towering math background said a few years ago, "I remember when math was easy -- back when I had time." Math that we've learned and mastered is "easy", but new areas of math can require a LOT of mental energy to gain traction in.