Full Idea
To a first approximation, P is correctly conceivable iff it would be conceivable for a logically ominiscient being who was fully informed about the nature of things.
Gist of Idea
A proposition is 'correctly' conceivable if an ominiscient being could conceive it
Source
Gideon Rosen (The Limits of Contingency [2006], 05)
Book Reference
'Identity and Modality', ed/tr. MacBride,Fraser [OUP 2006], p.23
A Reaction
Isn't the last bit covered by 'ominiscient'? Ah, I think the 'logically' only means they have a perfect grasp of what is consistent. This is to meet the standard problem, of ill-informed people 'conceiving' of things which are actually impossible.