Comment by _as_text

I really like this. I remember my first serious math book, which was this old-school set theory and topology book, and being all excited about learning set theory up until I encountered iterated Cartesian product, and was forced to accept that ((x, y), z) and (x, (y, z)) are supposed to be indistinguishable to me. An answer on StackExchange said that "you will never, ever, ever need to worry about the details of set theory", but I still did.