Full Idea
Validity is governed by epistemic necessity, i.e. an argument is valid if and only if there is an a priori route from premises to conclusion.
Gist of Idea
An argument is only valid if it is epistemically (a priori) necessary
Source
Dorothy Edgington (Two Kinds of Possibility [2004], §V)
A Reaction
Controversial, and criticised by McFetridge and Rumfitt. I don't think I agree with her. I don't see validity as depending on dim little human beings.