Full Idea
General and universal belong, not to the real existence of things, but are the inventions and creatures of the understanding, made by it for its own use, and concern only signs, whether words, or ideas.
Gist of Idea
Universals do not exist, but are useful inventions of the mind, involving words or ideas
Source
John Locke (Essay Conc Human Understanding (2nd Ed) [1694], III.3.11)
Book Reference
Locke,John: 'Essay Concerning Human Understanding', ed/tr. Nidditch,P.H. [OUP 1979], p.414
A Reaction
This places Locke as a thoroughgoing nominalist. However, while the most basic question of all is said to be 'why does anything exist?', another pretty good one is 'Why do things resemble one another?'. Maybe the universal had to come first?