Ideas from 'Barcan Formulae' by Koen Vervloesem [2010], by Theme Structure

[found in 'Key Terms in Logic' (ed/tr Williamson,J/Russo,F) [Continuum 2010,978-1-8470-6114-0]].

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4. Formal Logic / D. Modal Logic ML / 7. Barcan Formula
Barcan:nothing comes into existence; Converse:nothing goes out; Both:domain is unchanging
                        Full Idea: Intuitively, the Barcan formula says that nothing comes into existence when moving from a possible world to an alternative world. The converse says that nothing goes out of existence. Together they say the domain of quantification is fixed for all worlds.
                        From: Koen Vervloesem (Barcan Formulae [2010])
                        A reaction: Stated so clearly, they sound absurd. The sensible idea, I suppose, is that you can refer to all the things from any world, but that doesn't mean they are possible. Shades of Meinong. 'Square circles' are not possible.