Beginning Category Theory: Chs 1 to 6

Slow progress, but some progress is better than none. So here are Chapters 1 to 6 of Beginning Category Theory. The chapters are

  1. Introduction [The categorial imperative!]
  2. One structured family of structures. [Revision about groups, and categories of groups introduced]
  3. Groups and sets [Why I don’t want to assume straight off the bat that structures are sets]
  4. Categories defined [General definition, and lots of standard examples]
  5. Diagrams [Reading commutative diagrams]
  6. Categories beget categories [Duals of categories, subcategories, products, slice categories, etc.]

Both Chs 2 and 3 are mildly revised from the posting a week or so back. Chapters 4 to 6 are tidier versions of what were Chapters 3 and 4 in the old Category Theory: A Gentle Introduction. And so these six chapters taken together replace the first four of the Gentle Intro.

The Stage 1 plan over the coming weeks is to correct/smooth the existing content from the Gentle Intro. Stage 2 will then be to round out that content (same or closely related topics, same level, but improved examples, etc.). Stage 3 will be to push on to a look at a few more topics I want to cover.

Updated: The definition of a commutative diagram improved.

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