Full Idea
If I buy two toothbrushes on a 'buy one, get one free' offer, which one did I buy and which one did I get free? Those who believe that each contingent truth has a truthmaker are forced to believe that 'buy one, get one free' is false.
Gist of Idea
Which toothbrush is the truthmaker for 'buy one, get one free'?
Source
Roy Sorensen (Vagueness and Contradiction [2001], 11.6)
Book Reference
Sorensen,Roy: 'Vagueness and Contradiction' [OUP 2004], p.183
A Reaction
Nice. There really is no fact of which toothbrush is the free one. The underlying proposition must presumably be 'two for the price of one'. But you could hardly fault the first slogan under the Trades Descriptions Act.