9 ideas
14626 | In S5 matters of possibility and necessity are non-contingent [Williamson] |
13832 | Natural deduction shows the heart of reasoning (and sequent calculus is just a tool) [Gentzen, by Hacking] |
14625 | Necessity is counterfactually implied by its negation; possibility does not counterfactually imply its negation [Williamson] |
14623 | Strict conditionals imply counterfactual conditionals: □(A⊃B)⊃(A□→B) [Williamson] |
14624 | Counterfactual conditionals transmit possibility: (A□→B)⊃(◊A⊃◊B) [Williamson] |
14531 | Rather than define counterfactuals using necessity, maybe necessity is a special case of counterfactuals [Williamson, by Hale/Hoffmann,A] |
5987 | Alcmaeon was the first to say the brain is central to thinking [Alcmaeon, by Staden, von] |
14628 | Imagination is important, in evaluating possibility and necessity, via counterfactuals [Williamson] |
24043 | Soul must be immortal, since it continually moves, like the heavens [Alcmaeon, by Aristotle] |