 Essentialism has recently become a major area of investigation in the epistemology of modality. Essentialist accounts of modal knowledge draw on results from recent metaphysical debates about essence. Generally, metaphysical  essentialism  is the thesis that, in addition to mere accidental properties, entities also have essential properties. Traditionally, essential properties have been analyzed as those that necessarily belong to the objects that they pertain to. In his influential (1994) article, however, Kit Fine has argued against this analysis or reduction of essence to necessity. Fine provides counterexamples to the traditional view by pointing out that there are properties that an entity \(x\) has necessarily, though it is plausible that they do not belong to the essence of \(x.\) The notion of essence that Fine is working with is a broadly Aristotelian notion, according to which the essence of an entity \(x\) is the real definition of \(x\). Real definitions are contrasted against nominal definitions. Nominal definitions define words that stand for entities in the world, while real definitions define entities themselves by telling us what is essential to them. (Note that the explanation of essence in terms of real definition is not intended to be a reductive one.) For example, the nominal definition of “water” is, say, the drinkable liquid that is found in rivers and lakes on Earth, while the real definition of water is H2O. (Note that, besides Aristotle, this definitional notion of essence is already present in  Locke  and  Husserl.)