Full Idea
Existence is a property universal to all objects that exist, somewhat like self-identity, but less universal, because self-identity holds of all conceivable objects, not merely those that happen to exist.
Gist of Idea
Existence is a property of all objects, but less universal than self-identity, which covers even conceivable objects
Source
Colin McGinn (Logical Properties [2000], Ch.2)
Book Reference
McGinn,Colin: 'Logical Properties' [OUP 2003], p.30
A Reaction
This is a splendidly defiant response to the Kantian slogan that 'existence is not a predicate', and I find McGinn persuasive. I can still not find anyone to explain to me exactly what a property is, so I will reserve judgement.