4 ms·It is, after all, just a monoid in the category of endofunctors.by tiddles 4y agoIt is, after all, just a monoid in the category of endofunctors.olalonde 4y agoThanks, it all clicked now.WoahNoun 4y agoThis is a famous quote from the first real book on category theory. "Categories for the Working Mathematician" by Saunders Mac Lane.