In philosophy, essence is the attribute or set of attributes that make an object or substance what it fundamentally is, and which it has by necessity, and without which it loses its identity. Essence is contrasted with accident: a property that the object or substance has contingently, without which the substance can still retain its identity. The concept originates with Aristotle, who used the Greek expression to ti ên einai, literally 'the what it was to be', or sometimes the shorter phrase to ti esti, literally 'the what it is,' for the same idea. This phrase presented such difficulties for his Latin translators that they coined the word essentia to represent the whole expression. For Aristotle and his scholastic followers the notion of essence is closely linked to that of definition (horismos)

In the history of western thought, essence has often served as a vehicle for doctrines that tend to individuate different forms of existence as well as different identity conditions for objects and properties; in this eminently logical meaning, the concept has given a strong theoretical and common-sense basis to the whole family of logical theories based on the "possible worlds" analogy set up by Leibniz and developed in the intensional logic from Carnap to Kripke, which was later challenged by "extensionalist" philosophers such as Quine.

The English word "essence" comes from the Latin essentia, which was coined (from the Latin esse, "to be") by ancient Roman scholars in order to translate the Ancient Greek phrase to ti ēn einai (literally, "what it is for a thing to be"), coined by Aristotle to denote a thing's essence.

Ontologic status

According to Plato, essences are eide; species and forms separate of the sense's things. These forms are models of the sense's things, and represent genuine reality; sense's world is less reality; for instance, justice in relation to just actions. These forms are pure and eternal forms.

Aristotle moves the forms of Plato to the nucleus of the individual thing, which is called ousía or substance. Essence is the tí of the thing, the to tí en einai. Essence corresponds to the ousia's definition; essence is a real and physical aspect of the ousía. (Aristotle, "Metaphisic", I)

According to nominalists (Roscelin of Compiègne, William of Ockham, John Duns Scoto, William of Champeaux, Bernard of Chartres), universals aren't concrete entities, just voice's sounds; there are only individuals: "nam cum habeat eorum sententia nihil esse praeter individuum(...)" (Roscelin, De gener. et spec., 524). Universals are words that can to call several individuals; for example the word "homo". Therefore a universal is reduced to a sound's emission. (Roscelin, "De generibus et speciebus")

According to Edmund Husserl essence is ideal. However, ideal means that essence is the intentional object of the conscience. Essence is interpreted as sense. (E. Husserl, "Ideas pertaining to a pure phenomenology and to a phenomenological philosophy", paragraphs 3 and 4).