 As Cartwright (1954) observed, it is far from clear how one is supposed to interpret the modality in Quine’s official formulation of the criterion. A purely extensional version of the criterion is plainly inadequate: \(T\) is ontologically committed to objects of kind \(K\) if, and only if, \(T\) is true only if the variables range over objects of kind \(K\). But the material conditional is much too weak for Quine’s purposes as it makes any false theory to be ontologically committed to all kinds of  objects.[19]  Quine’s general hostility to non-extensional notions makes the problem all the more delicate for him.