Beginning Category Theory: Chs 1 to 9

Slow progress again but, as I said before, any progress is better than none. So here are Chapters 1 to 9 of Beginning Category Theory. [As always you may need to force a reload to get the latest version.]

And no, there isn’t really a new chapter. I’ve split what was becoming a baggy chapter about kinds of arrows into two, and I hope to have made some of it a fair bit clearer and better organised. The chapters are

Introduction [The categorial imperative!]One structured family of structures. [Revision about groups, and categories of groups introduced]Groups and sets [Why I don’t want to assume straight off the bat that structures are sets]Categories defined [General definition, and lots of standard examples]Diagrams [Reading commutative diagrams]Categories beget categories [Duals of categories, subcategories, products, slice categories, etc.]Kinds of arrows [Monos, epics, inverses]Isomorphisms [why they get defined as they do]Initial and terminal objects

Ch. 3 has been mildly revised again, and as I said Ch.7 has been significantly improved. Various minor typos have been corrected. And there have been quite a few small stylistic improvements (including, I’m embarrassed to say, deleting over 50 occurrences of the word “indeed” …).

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