Disjunction, Conjunction and Categories

This paper examines some taken-for-granted themes from an unusual angle. It might be analytical, but (it is hoped) none the worse for that.
We cannot deal only in single instances. Our brains would be overwhelmed. So, we take refuge in generalisations of one kind or another that can be containers into which single instances can conveniently be put. This paper
explores some of the containers we use: sets; categories; norms; rules; principles. With an eye on the notion of a ‘common law method’, it attempts
to illuminate their characteristics and usages. In so doing, it must confront:
(i) separation-combination ambiguity and (ii) conceptions of similarity and difference.
Although concentrating on the ‘how?’ of categorisation, this paper also suggests that, in the necessary categorisation process, we overestimate the separateness, and underestimate the malleability and temporality, of the categories we contrive. In short, the process and its resulting categories are — despite their appearances and common attitudes to them — mind-dependent and not Platonistic.