 One of Quine’s arguments is that synonymy is not a well-defined equivalence relation, the identity conditions for propositions are unclear and there is ‘no entity without identity’. On this issue, Grice is not committed to an equivalence relation of synonymy (thus his remark above about indeterminacy), and he parts company with Quine over whether clear identity conditions are required. Grice, as noted earlier, argues for such conditions. But the acceptability of his theory of meaning does not depend on the success of that defense. Within the theory of meaning, propositions are theoretical entities to be understood by the role in the theory, and that role, according to Grice, does not demand a strict criterion of identity. Rather: if they work they exist. It is worth noting in this regard that there are many respectable entities for which we do not have criteria or identity. Suppose my favorite restaurant moves. Is it a new restaurant with the same name? Or suppose it changes owners and names but nothing else? Or that it changes menu entirely? Or that it changes chefs? It would be foolish to look for a single criterion to answer these questions—the answers go different ways in different contexts. But surely the concept of a restaurant is a useful one and restaurants do exists. Quine and Grice differ on the theoretical usefulness of propositions. The main reason for disagreement is due to Quine’s attitude that concepts such as belief and desire are of, at most, secondary importance in the unified canonical science that is his standard for ontology. Grice, as we have already noted, thinks that everyday psychological theory is of first importance.