Full Idea
Parmenides was correct - one cannot speak of that which is not, even to say that it is not. But one can speak of concepts and say of them that they do not correspond to anything real.
Gist of Idea
We cannot pick out a thing and deny its existence, but we can say a concept doesn't correspond
Source
C. Anthony Anderson (Identity and Existence in Logic [2014], 2.5)
Book Reference
'Bloomsbury Companion to Philosophical Logic', ed/tr. Horsten,L/Pettigrew,R [Bloomsbury 2014], p.71
A Reaction
[This summarises Alonso Church, who was developing Frege] This sounds like the right thing to say about non-existence, but then the same principle must apply to assertions of existence, which will also be about concepts and not things.
Related Idea
Idea 18767 Free logics has terms that do not designate real things, and even empty domains [Anderson,CA]