Full Idea
To have a property is to be a member of a class, usually a class of things. (Note: this resembles the doctrine of Class Nominalism, but I do not claim to solve the One Over Many problem by this means, far from it).
Gist of Idea
To have a property is to be a member of a class, usually a class of things
Source
David Lewis (New work for a theory of universals [1983], 'Un and Prop')
Book Reference
'Properties', ed/tr. Mellor,D.H. /Oliver,A [OUP 1997], p.189
A Reaction
Lewis remains neutral about the traditional question of whether universals exist. What does he mean by "is" in his assertion? Identity, predication or class membership? I think Lewis is open to many of the objections to Class Nominalism.