Full Idea
There are no such things as numbers in the abstract.
Gist of Idea
There are no such things as numbers in the abstract
Source
John Stuart Mill (System of Logic [1843], 2.6.2)
Book Reference
Mill,John Stuart: 'System of Logic (9th ed, 2 vols)' [Longmans, Green etc 1875], p.293
A Reaction
Depends. Would we want to say that 'horses don't exist' (although each individual horse does exist)? It sounds odd to say of an idea that it doesn't exist, when you are currently thinking about it. I am, however, sympathetic to Mill.