 Searle (1958) responds to the epistemic argument (see  Section 2.3)  by proposing a cluster theory. That argument seemed to show that individual components of the cluster, such as taught Plato, could not be necessary conditions on belonging to the name’s extension. For otherwise it would be knowable a priori that Socrates taught Plato. (Note that there is a similar problem with treating it as a sufficient condition; for then it would be a priori that no-one other than Socrates taught Plato.) Instead, Searle suggests that a name’s meaning imposes the weaker requirement that some member of the cluster be true of the referent. On his account, it is only a priori that the referent possesses the disjunction of the conditions of the cluster. (Note that this weak condition is unlikely to single out a referent for the name; hence Searle does not seem to provide a complete picture of reference determination. But strengthening the account would only make the a priori consequences stronger.)