Juan wrote:

> After having read over it, the paper mentions "monoidal categories". As the second chapter of the _Seven Sketches_ book is about "monoidal preorders", maybe exploring both things in parallel can make sense, don't you think?

Monoidal categories - categories where you can multiply objects and morphisms - are pretty fundamental to mathematics. Just as preorders are a special case of categories, monoidal preorders are a special case of monoidal categories. _Seven Sketches_ is highly unorthodox in that it discussses preorders and monoidal preorders before turning to more general categories and monoidal categories. But with luck, by the end, you'll be experts on all these things!