A revised version of *Category Theory I* is now online. The main substantive change is a rather more consistent handling of plural notation; but there are a couple more theorems and some scattered improvements in explanations and a few typos corrected.

There is a corresponding new version of *Category Theory II* but the only changes are ones to automatically update cross references to *Category Theory I.*

I plan over June to turn *Category Theory I* into a very cheap paperbacked Big Red Logic book (though it will of course still be free to download as a PDF). The text still won’t be set in stone — in fact, I’ll call it a β-version. But it will be a lot nicer to work from.

I plan to add one more chapter, on ‘the elementary theory of the category of sets’ as all the pieces are in place to cover that. I have a fairly short current list of previous episodes I want to improve, though I will no doubt find more; I want to add more signalling about which more techie bits can be skipped by those wanting a less proof-heavy (initial) read; I’ll add an index. So if you have been meaning to drop me a note with comments/suggestions/corrections *now* is the time to do so!

Current versions of *Category Theory I* and *II* can be downloaded here.

*Added June 6*: Minor revisions and typo-corrections for Chapters 1 to 6 uploaded.

LiviuKeep up your excellent work! This is one of the very few blogs I enjoy reading on daily basis! Best regards!