Single Idea 19067

[catalogued under 2. Reason / E. Argument / 6. Conclusive Proof]

Full Idea

For a demonstration to be cogent it is necessary that the passage from step to step involve a recognition of truth at each line.

Gist of Idea

A successful proof requires recognition of truth at every step

Source

Michael Dummett (The Justification of Deduction [1973], p.313)

Book Reference

Dummett,Michael: 'Truth and Other Enigmas' [Duckworth 1978], p.313


A Reaction

Dummett cited Quine (esp. 1970) as having an almost entirely syntactic view of logic. Rumfitt points out that logic can move validly from one falsehood to another. Even a 'proof' might detour into falsehood, but it would not be a 'canonical' proof!