more from E.J. Lemmon

Single Idea 9508

[catalogued under 4. Formal Logic / B. Propositional Logic PL / 2. Tools of Propositional Logic / a. Symbols of PL]

Full Idea

I introduce the sign |- to mean 'we may validly conclude'. To call it the 'assertion sign' is misleading. It may conveniently be read as 'therefore'.

Gist of Idea

The sign |- may be read as 'therefore'


E.J. Lemmon (Beginning Logic [1965], 1.2)

Book Reference

Lemmon,E.J.: 'Beginning Logic' [Nelson 1979], p.11

A Reaction

[Actually no gap between the vertical and horizontal strokes of the sign] As well as meaning 'assertion', it may also mean 'it is a theorem that' (with no proof shown).