Full Idea
Existence is like a primary quality; non-existence is like a secondary quality.
Gist of Idea
Existence is a primary quality, non-existence a secondary quality
Source
Colin McGinn (Logical Properties [2000], Ch.2 n29)
Book Reference
McGinn,Colin: 'Logical Properties' [OUP 2003], p.43
A Reaction
Since McGinn thinks existence really is a property, and hence, presumably, a predicate, I don't quite see why he uses the word "like". A nicely pithy and thought-provoking remark.