Combining Philosophers

Ideas for John Dupré, Trenton Merricks and Auguste Comte

unexpand these ideas     |    start again     |     choose another area for these philosophers

display all the ideas for this combination of philosophers

---

2 ideas

4. Formal Logic / D. Modal Logic ML / 1. Modal Logic

19209	Simple Quantified Modal Logc doesn't work, because the Converse Barcan is a theorem [Merricks]
	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.
	From: Trenton Merricks (Propositions [2015], 2.V)
	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.

4. Formal Logic / D. Modal Logic ML / 7. Barcan Formula

19208	The Converse Barcan implies 'everything exists necessarily' is a consequence of 'necessarily, everything exists' [Merricks]
	Full Idea: The Converse Barcan Formula has a startling result. Simple Quantified Modal Logic (SQML) has the following as a theorem: □∀xFx → ∀x□Fx. So 'everything exists necessarily' is a consequence of 'necessarily, everything exists'.
	From: Trenton Merricks (Propositions [2015], 2.V)
	A reaction: He says this is blatantly wrong. Williamson is famous for defending it. I think I'm with Merricks on this one.