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.