Single Idea 13347

[catalogued under 5. Theory of Logic / B. Logical Consequence / 4. Semantic Consequence |=]

Full Idea

The classical definition of validity counts an argument as valid if and only if the conclusion does in fact follow from the premises, whether or not the argument contains any demonstration of this fact.

Gist of Idea

Validity is a conclusion following for premises, even if there is no proof

Source

David Bostock (Intermediate Logic [1997], 1.2)

Book Reference

Bostock,David: 'Intermediate Logic' [OUP 1997], p.5


A Reaction

Hence validity is given by |= rather than by |-. A common example is 'it is red so it is coloured', which seems true but beyond proof. In the absence of formal proof, you wonder whether validity is merely a psychological notion.