Full Idea
In general, if completeness fails there is no algorithm to list the valid formulas.
Gist of Idea
If completeness fails there is no algorithm to list the valid formulas
Source
Leslie H. Tharp (Which Logic is the Right Logic? [1975], §2)
Book Reference
'Philosophy of Logic: an anthology', ed/tr. Jacquette,Dale [Blackwell 2002], p.38
A Reaction
I.e. the theory is not effectively enumerable.