Full Idea
The imaginability test of possibility confuses what is really or metaphysically possible with what is only epistemically possible. ..The latter is just what is possible for all we know.
Gist of Idea
Imagination tests what is possible for all we know, not true possibility
Source
Brian Ellis (The Philosophy of Nature: new essentialism [2002], Ch.6)
Book Reference
Ellis,Brian: 'The Philosophy of Nature: new essentialism' [Acumen 2002], p.114