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Single Idea 19215

[catalogued under 2. Reason / E. Argument / 1. Argument]

Full Idea

There is a seasoned method of turning your opponent's modus ponens into your own modus tollens.

Gist of Idea

Arguers often turn the opponent's modus ponens into their own modus tollens


Trenton Merricks (Propositions [2015], 5.VII)

Book Reference

Merricks,Trenton: 'Propositions' [OUP 2015], p.182

A Reaction

That is, they say 'if he's coming he'll be hear by now, and he's definitely coming', to which you say 'I'm afraid he's not here, so he obviously isn't coming after all'. They say if-A-then-B, and A, so B. You say not-B, so you're wrong about A.

Related Idea

Idea 5395 Demonstration always relies on the rule that anything implied by a truth is true [Russell]