Full Idea
If an abstract object exists only when there is some suitable way of expressing it, then there are at most denumerably many abstract objects.
Gist of Idea
If abstracta only exist if they are expressible, there can only be denumerably many of them
Source
David Bostock (Philosophy of Mathematics [2009], 8.2)
Book Reference
Bostock,David: 'Philosophy of Mathematics: An Introduction' [Wiley-Blackwell 2009], p.242
A Reaction
Fine by me. What an odd view, to think there are uncountably many abstract objects in existence, only a countable portion of which will ever be expressed! [ah! most people agree with me, p.243-4]