Full Idea
Conditional Proof seems sound: 'From X and Y, it follows that Z. So from X it follows that if Y,Z'. Yet for no reading of 'if' which is stronger that the truth-functional reading is CP valid, at least if we accept ¬(A&¬B);A; therefore B.
Gist of Idea
Conditional Proof is only valid if we accept the truth-functional reading of 'if'
Source
Dorothy Edgington (Conditionals (Stanf) [2006], 2.2)
Book Reference
'Stanford Online Encyclopaedia of Philosophy', ed/tr. Stanford University [plato.stanford.edu], p.5
A Reaction
See the section of ideas on Conditionals (filed under 'Modality') for a fuller picture of this issue. Edgington offers it as one of the main arguments in favour of the truth-functional reading of 'if' (though she rejects that reading).
Related Idea
Idea 14274 Inferring conditionals from disjunctions or negated conjunctions gives support to truth-functionalism [Edgington]