He’s saying that he made up categories and functors because what he really wanted to study was the idea of natural transformations, and the former notions are needed to define the latter. Or: categories and functors are nice, but natural transformations are the bomb.
He’s saying that he made up categories and functors because what he really wanted to study was the idea of natural transformations, and the former notions are needed to define the latter. Or: categories and functors are nice, but natural transformations are the bomb.