The objection is misguided if directed at the quantifier criterion as it has standardly been interpreted (and was interpreted by Quine). The quantifier criterion was not designed to be sensitive to whether the entities assumed by a theory are fundamental or derived (see §3.2 below). If the values of the bound variables must include Ks, then the theory is ontologically committed to Ks, whether Ks are fundamental or derived. That is simply how the criterion is to be understood. If we want a way to distinguish between ontological commitments to fundamental kinds and ontological commitments to derived kinds, we need to look elsewhere.