The discussion centers on finding resources for learning category theory without relying on set theory. A key reference mentioned is MacLane's "Categories for the Working Mathematician," which includes a section on foundational aspects of category theory. The conversation also touches on related topics such as topos theory, with participants noting their interest in works like Mac Lane's "Sheaves in Geometry and Logic" and Goldblatt's "Topoi." Additionally, there is mention of a paper that axiomatizes a large category without formal set theory, which could be of interest to those exploring category theory's foundations. Overall, the thread highlights a search for alternative approaches to understanding category theory beyond traditional set-theoretic frameworks.