more from Jennifer Fisher

Single Idea 8951

[catalogued under 5. Theory of Logic / A. Overview of Logic / 6. Classical Logic]

Full Idea

For simplicity, we can say that 'classical logic' amounts to the truth of four sentences: 1) either p or not-p; 2) it is not the case that both p and not-p; 3) from p and not-p, infer q; 4) from p or q and not-p, infer q.

Gist of Idea

Classical logic is: excluded middle, non-contradiction, contradictions imply all, disjunctive syllogism


Jennifer Fisher (On the Philosophy of Logic [2008], 12.I)

Book Reference

Fisher,Jennifer: 'On the Philosophy of Logic' [Thomson Wadsworth 2008], p.162

A Reaction

[She says there are many ways of specifying classical logic] Intuition suggests that 2 and 4 are rather hard to dispute, while 1 is ignoring some grey areas, and 3 is totally ridiculous. There is, of course, plenty of support for 3!