Single Idea 5741

[catalogued under 5. Theory of Logic / J. Model Theory in Logic / 1. Logical Models]

Full Idea

In first-order predicate calculus validity is defined thus: an argument is valid iff every model that makes the premises of the argument true also makes the conclusion of the argument true.

Clarification

'Iff' means if and only if

Gist of Idea

If every model that makes premises true also makes conclusion true, the argument is valid

Source

Joseph Melia (Modality [2003], Ch.2)

Book Reference

Melia,Joseph: 'Modality' [Acumen 2003], p.48


A Reaction

See Melia Ch. 2 for an explanation of a 'model'. Traditional views of validity tend to say that if the premises are true the conclusion has to be true (necessarily), but this introduces the modal term 'necessarily', which is controversial.