To make sense of the world, we rely on our brains’ capability to form fictions that we call ”categories” of things and experiences. This capability is both automatic and hidden: we can’t avoid doing it, yet we don’t know exactly how we do it. We know that differences and similarities play a role, but how? When we try to be more deliberate about the process, for instance because we want to write software based on our categories, we call it modelling. In the process, we tend to replace our intuitive but ill-defined common-sense categories with more precise technical categories. But precision comes at a cost. In this talk, we’ll look at different perspectives on categorization, see that nothing remains the same for long, and that edge cases are just regular cases that got unlucky.