Nonexistence

Existence is the state of being real or participating in reality. The terms "being", "reality", and "actuality" are often used as close synonyms. Existence contrasts with nonexistence, nothingness, and nonbeing. A common distinction is between the existence of an entity and its essence, which refers to the entity's nature or essential qualities.

The main philosophical discipline studying existence is called ontology. The orthodox view is that it is a second-order property or a property of properties. According to this view, to say that a thing exists means that its properties are instantiated. A different view holds that existence is a first-order property or a property of individuals. This means that existence has the same ontological status as other properties of individuals, like color and shape. Meinongians accept this idea and hold that not all individuals have this property: they state that there are some individuals that do not exist. This view is rejected by universalists, who see existence as a universal property of every individual.

Various types of existence are discussed in the academic literature. Singular existence is the existence of individual entities while general existence refers to the existence of concepts or universals. Other distinctions are between abstract and concrete existence, between possible, contingent, and necessary existence, and between physical and mental existence. A closely related issue is whether different types of entities exist in different ways or to different degrees.

A key question in ontology is whether there is a reason for existence in general or why anything at all exists. The concept of existence is relevant to various fields, including logic, epistemology, philosophy of mind, philosophy of language, and existentialism.