1. Theory T implies judgment J.The arguer is saying that 1 and 2 entail 3, which is equivalent to saying that the following three propositions are inconsistent:
2. Not J.
3. Not T.
Theory T implies judgment J.Since the argument is valid (an instance of modus tollens), these three propositions are inconsistent. Therefore, at least one of them is false. But which one? Here there can be disagreement. Someone could reject the first proposition by saying that T, properly understood, doesn't imply J. Or someone could bite the bullet and reject the second proposition (i.e., affirm J). Or someone could reject the third proposition. This person has been persuaded by the argument.
Feldman seemed to ignore the first two possibilities, which always puzzled me. For readers who wonder about such things, here is a link to Feldman's essay.