 Three points need to be made here. First, the above criterion needs to be generalized so that it covers the use of singular terms in other kinds of sentences, e.g., sentences of the form ‘a is R-related to b’. Second, on the standard view, we are ontologically committed not just by singular terms but also by existential statements — e.g., by sentences like ‘There are some Fs’, ‘There is at least one F’, and so on (in first-order logic, such sentences are symbolized as ‘(∃x)Fx’, and the ‘∃’ is called an existential quantifier). The standard view here is that if you think that a sentence like this is true, then you are committed to believing in the existence of some Fs (or at least one F) but you do not have to believe in Fness; for instance, if we assent to ‘There are some dogs’, then we are committed to believing in the existence of some dogs, but we are not thereby committed to believing in the existence of the property of doghood. (Quine actually thought that we are committed only by existential claims and not by singular terms; but this is not a widely held view.) Third and finally, it is usually held that we are ontologically committed by singular terms and existential expressions (or existential quantifiers) only when they appear in sentences that we think are literally true and only when we think the singular term or existential quantifier in question can't be paraphrased away. We can see what's meant by this by returning to the sentence