Single Idea 12192

[catalogued under 10. Modality / A. Necessity / 6. Logical Necessity]

Full Idea

The manifestation of the belief that a mode of inference is logically necessarily truth-preserving is the preparedness to employ that mode of inference in reasoning from any set of suppositions whatsoever.

Gist of Idea

The mark of logical necessity is deduction from any suppositions whatever

Source

Ian McFetridge (Logical Necessity: Some Issues [1986], 4)

Book Reference

-: 'Aristotelian Society' [], p.153


A Reaction

He rests this on the idea of 'cotenability' of the two sides of a counterfactual (in Mill, Goodman and Lewis). There seems, at first blush, to be a problem of the relevance of the presuppositions.