Full Idea
If something is true, then it would not be possible for it to be false unless either certain things were to exist which don't, or else certain things had not existed which do.
Gist of Idea
Truth and falsehood must track what does or doesn't exist
Source
John Bigelow (The Reality of Numbers [1988], 19)
Book Reference
Bigelow,John: 'The Reality of Numbers' [OUP 1988], p.133
A Reaction
This is described by Rami as Bigelow's 'famous' formulation of the idea that 'truth supervenes on being' in a general way. An immediate question would be about fictions. Is Malvolio a stupid man, given that he doesn't exist? We must stretch 'exist'.