 Assuming that we have knowledge of some essentialist claims, how might we account for that knowledge? For the purposes of the present discussion, let us assume that we know that being such that there are infinitely many primes, being human, and originating from sperm \(s\) and egg \(e\) are essential properties of Socrates. The first example is different from the last two in that it seems that we can know a priori that being such that there are infinitely many primes is essential to Socrates whereas it seems that we can know only a posteriori that being human and originating from \(s\) and \(e\) are also essential to him.