Single Idea 14358

[catalogued under 10. Modality / B. Possibility / 8. Conditionals / d. Non-truthfunction conditionals]

Full Idea

In the possible worlds account modus ponens is validated (the closest world, the actual, is a B-world just if B is true), and modus tollens is validated (if B is false, the actual world is not an A-world, so A is false).

Gist of Idea

In the possible worlds account of conditionals, modus ponens and modus tollens are validated

Source

Frank Jackson (Conditionals [2006], 'Famous')

Book Reference

'Blackwell Guide to Philosophy of Language', ed/tr. Devitt,M/Hanley,R [Blackwell 2006], p.216


A Reaction

[see Jackson for slightly fuller versions] This looks like a minimal requirement for a decent theory of conditionals, so Jackson explains the attractions of the possible worlds view very persuasively.