Full Idea
Subscribers to the Barcan formula must either be committed to the existence of mere possibilia (such as possible unicorns), or deny many unactualised possibilities of existence.
Gist of Idea
The Barcan formula endorses either merely possible things, or makes the unactualised impossible
Source
Barbara Vetter (Potentiality [2015], 7.5)
Book Reference
Vetter,Barbara: 'Potentiality: from Dispositions to Modality' [OUP 2015], p.267
A Reaction
It increasingly strikes me that the implications of the Barcan formula are ridiculous. Williamson is its champion, but I'm blowed if I can see why. What could a possible unicorn be like? Without them, must we say unicorns are impossible?