  Following Aristotle's lead, a most economical way to account for the cognitive superiority of Forms and the inferiority of sensibles would be to allot essences only to the Forms. Since we know from the early and the middle dialogues that knowledge is of essence, it is tempting to think that the absence of essence is responsible for the deficiency of the particulars. Particulars are deficient because they can or do change. They change because their properties are contingent. Their properties are contingent because they lack any essences (or any essential properties). But this is too quick. First, Plato's particulars may not change with respect to all of their properties. Perhaps some have essential properties along with a host of contingent properties. Then Aristotle might be taken to imply that only with respect to a certain number of contingent properties did Plato posit definable Forms. Moreover, Aristotle seems to allude only to an epistemological difficulty arising from changing particulars. It is possible that this difficulty arises independently of whether some particulars have essential properties. For instance, particulars might be epistemologically problematic because they have many properties, only some of which are changing.