Full Idea
How likely is a fair die landing on an even number to land six? My approach is, assume an even number, so three possibilities, one a six, so 'one third'; the truth-functional approach is it's true if it is not-even or six, so 'two-thirds'.
Gist of Idea
Truth-functional possibilities include the irrelevant, which is a mistake
Source
Dorothy Edgington (Do Conditionals Have Truth Conditions? [1986], 3)
Book Reference
'A Philosophical Companion to First-Order Logic', ed/tr. Hughes,R.I.G. [Hackett 1993], p.36
A Reaction
The point is that in the truth-functional approach, if the die lands not-even, then the conditional comes out as true, when she says it should be irrelevant. She seems to be right about this.