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I hope most mathematicians continue to fear and despise category theory, so I can continue to maintain a certain advantage over them.

The above is a graph of the number of times the phrase “category theory” has been used in books, from about 1950 through the present. It speaks for itself.

But why? What’s the big deal? Why does category theory matter? I’m about a quarter of the way through Conceptual Mathematics: A First Introduction to Categories and still not sure why I’m bothering with fleshing out all this theory. Is this just set theory for hipsters?

Category theory is, essentially, the study of mathematical structure. It’s the study of things and the mappings between those things, the translations of these objects. These are usually called objects and morphisms (or arrows, if you prefer). Objects can be thought of as sets and arrows as functions, though they are not limited to this interpretation.

The subject’s major insight is, in order to understand something, focus on the structure preserving mappings of that something — the legal translations.

Read more rs.io/why-ca...