The restriction to theories couched within first-order predicate logic is severe. Philosophers have been no less interested in the ontological commitments of theories couched within other logical frameworks, such as higher-order or intensional logics (see §1.7.2 and §1.7.3). Worse, if the criterion is to have application to the actual ontological debates among philosophers, it will have to apply to theories couched within ordinary language as well. This led Quine—at least sometimes—to endorse an extended criterion of ontological commitment: a theory is ontologically committed to an entity or kind of entity if and only if every acceptable paraphrase of the theory into (austere) first-order predicate logic is ontologically committed to that entity or kind of entity. This provides philosophers with a method for avoiding ontological commitment: find an acceptable paraphrase of the theory into first-order predicate logic that is not ontologically committed to the questionable entities (Quine 1948: 32, 1953: 103–104). (What counts as an “acceptable paraphrase”, and whether any sort of “paraphrase” should be required, is discussed in §4.2.)