A second, more serious problem is that ontological commitment is entrapped in the object language: if ‘K’ is not a predicate of the object language, we have no way of assigning ontological commitment to Ks. Say that the explicit ontological commitments of a theory are given by the existential sentences that the theory logically entails.[9] The metalinguistic criterion above takes all ontological commitment to be explicit ontological commitment. But ontological commitment can fail to be explicit—or so it appears—in one of two ways. A theory may have implicit ontological commitments by entailing existential sentences or propositions according to some entailment relation more generous than logical entailment (see §1.5 and §2). Or a theory may have implicit ontological commitments by entailing existential propositions that are not expressible in the language of the theory. For example, a theory containing ‘∃x Elephant(x)’, one might hold, is ontologically committed to animals, whether or not the language of the theory contains the predicate ‘Animal’. A defender of the metalinguistic criterion, however, should simply deny that there are implicit ontological  commitments.[10]  As with the previous objection, we can enhance the theory by adding new predicates and new postulates involving the new predicates. Indeed, we can suppose that the object language is as rich as the metalanguage with respect to non-semantical predicates. Again, it is awkward to have to say that only the enhanced theory in the enhanced language, not the original theory in the original language, carries ontological commitment to animals. But, again, perhaps we can live with that. (For more on the problem of implicit commitment, see 1.7 and §2.1)