more from Stephen Read

Single Idea 14184

[catalogued under 5. Theory of Logic / B. Logical Consequence / 5. Modus Ponens]

Full Idea

A puzzle about modus ponens is that the major premise is either false or unnecessary: A, If A then B / so B. If the major premise is true, then B follows from A, so the major premise is redundant. So it is false or not needed, and contributes nothing.

Gist of Idea

In modus ponens the 'if-then' premise contributes nothing if the conclusion follows anyway


Stephen Read (Formal and Material Consequence [1994], 'Repres')

Book Reference

'Philosophy of Logic: an anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.243

A Reaction

Not sure which is the 'major premise' here, but it seems to be saying that the 'if A then B' is redundant. If I say 'it's raining so the grass is wet', it seems pointless to slip in the middle the remark that rain implies wet grass. Good point.