Editing Problem of universals (section)

===Armstrong===
The Australian philosopher [[David Malet Armstrong]] has been one of the leading realists in the twentieth century, and has used a concept of universals to build a naturalistic and scientifically realist ontology. In both ''Universals and Scientific Realism'' (1978) and ''Universals: An Opinionated Introduction'' (1989), Armstrong describes the relative merits of a number of nominalist theories which appeal either to "natural classes" (a view he ascribes to [[Anthony Quinton, Baron Quinton|Anthony Quinton]]), concepts, resemblance relations or predicates, and also discusses non-realist "trope" accounts (which he describes in the ''Universals and Scientific Realism'' volumes as "particularism"). He gives a number of reasons to reject all of these, but also dismisses a number of realist accounts.