What's the deal with category theory on HN? Seriously, how is it interesting or relevant without introducing it along with concepts from fields in which it is of main use (e.g. (homological) algebra and algebraic toplogy)? I don't think I'd be able to appreciate, or even understand CT without having a thorough understanding of concepts it tries to generalize -- hell, I do have trouble to consider it useful even with it. Since I do not believe that HN us full of mathematicians (even though there are a few) researching algebraic topology or homological algebra, I wonder who reads and posts such things here.