Full Idea
Jackson came to realise that there are assertable conditionals which one would not continue to believe if one learned the antecedent, such as Lewis's "If Reagan worked for the KGB, I'll never find out".
Gist of Idea
There are some assertable conditionals one would reject if one learned the antecedent
Source
report of Frank Jackson (Conditionals [1987]) by Dorothy Edgington - Conditionals (Stanf) 4.2
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.23
A Reaction
That pesky David Lewis made trouble for everybody. Edgington agrees that his earlier formulation (Idea 14288) holds good for nearly all cases. There is a self-referential element in Lewis's example.
Related Idea
Idea 14288 'If A,B' affirms that A⊃B, and also that this wouldn't change if A were certain [Jackson, by Edgington]