The physical page is 65, the labelled page is 57. That is of course, a joke, but Category Theory does feel like that sometimes. There does not appear to be any

The physical page is 65, the labelled page is 57. That is of course, a joke, but Category Theory does feel like that sometimes. There does not appear to be any grounding, it's all circular. Anything can be lifted-up, or projected forgetfully down, to almost anything else. A Category has sets of nodes and edges, to describe the category of ... SET. Category diagrams are directed graphs, and there is a category of GRAPH, which can be labelled to make a diagram, which can be used to analyze ... categories. There is always sand under your feet and concrete in the sky.