[nereye]

FWIW, there is a whole chapter (17 in the first edition, 20 in the third/current edition, don’t have a second edition in front of me but would be surprised if it didn’t have one) on Partial Differential Equations. It’s about 50+ pages in the first edition and 70+ in the third.

But I take your point, the chapter does admit to being intended as “the briefest possible useful introduction” and notes that the topic would require another volume entirely dedicated to it.

[throwaway81523]

Ah thanks, I must have mis-remembered. I think it did say something about PDE's being the dividing line though.