more from Trenton Merricks

Single Idea 19209

[catalogued under 4. Formal Logic / D. Modal Logic ML / 1. Modal Logic]

Full Idea

Logical consequence guarantees preservation of truth. The Converse Barcan, a theorem of Simple Quantified Modal Logic, says that an obvious truth implies an obvious falsehood. So SQML gets logical consequence wrong. So SQML is mistaken.

Gist of Idea

Simple Quantified Modal Logc doesn't work, because the Converse Barcan is a theorem


Trenton Merricks (Propositions [2015], 2.V)

Book Reference

Merricks,Trenton: 'Propositions' [OUP 2015], p.65

A Reaction

I admire this. The Converse Barcan certainly strikes me as wrong (Idea 19208). Merricks grasps this nettle. Williamson grasps the other nettle. Most people duck the issue, I suspect. Merricks says later that domains are the problem.

Related Idea

Idea 19208 The Converse Barcan implies 'everything exists necessarily' is a consequence of 'necessarily, everything exists' [Merricks]