A Puzzle about Hume’s Theory of General Representation

According to Hume’s theory of general representation, we represent generalities by associating certain ideas with certain words. On one understanding of this theory, calling things by a name does not represent any real qualities of those things or any real relations between them. This interpretation runs into difficulty when applied to Hume’s own use of such general terms throughout the Treatise. Because these distinctions do theoretical-explanatory work in Hume’s philosophical system, they require that the items so distinguished really are different. This reveals that Hume employs a more sophisticated understanding of the science of human nature than has previously been understood. While Hume is a thoroughgoing nominalist about terms in the language of the vulgar, he is a realist about the theoretical-explanatory terms of science.