Full Idea
No metaphysical account which renders it impossible to give a plausible epistemological theory is to be countenanced.
Gist of Idea
There must be a plausible epistemological theory alongside any metaphysical theory
Source
Graeme Forbes (The Metaphysics of Modality [1985], 9.1)
Book Reference
Forbes,Graeme: 'The Metaphysics of Modality' [OUP 1985], p.217
A Reaction
It is hard to object to this principle, though we certainly don't want to go verificationist, and thus rule out speculations about metaphysics which are beyond any possible knowledge. Some have tried to prove that something must exist (e.g. Jacquette).