Full Idea
A logic is 'free' to the degree it refrains from existential import of its singular and general terms. Classical logic must have non-empty domain, and each name must denote in the domain.
Gist of Idea
Free logic terms aren't existential; classical is non-empty, with referring names
Source
JC Beall / G Restall (Logical Pluralism [2006], 7.1)
Book Reference
Beall,J/Restall,G: 'Logical Pluralism' [OUP 2006], p.75
A Reaction
My intuition is that logic should have no ontology at all, so I like the sound of 'free' logic. We can't say 'Pegasus does not exist', and then reason about Pegasus just like any other horse.