Haha, it's like Maclane said: "I did not invent category theory to talk about functors. I invented it to talk about natural transformations." You gotta go at l

Haha, it's like Maclane said: "I did not invent category theory to talk about functors. I invented it to talk about natural transformations." You gotta go at least to the third level of abstraction to get the real meat.