One disputant admits:
“Anything meeting all the conditions of this definition belongs to the class.”
The disputant also admits:
“Case A meets all the stated conditions.”
It follows, on those premises, that “Case A belongs to the class.” If the conclusion is rejected, the disputant must challenge a premise, a term's meaning, or the inference.
This is a principled form of binding an interlocutor by their own concessions, rather than an appeal to rhetoric alone.