Does Santa Claus have being without existing? One philosopher said yes
Alexius Meinong argued that every object of thought has being, but only some of them exist. Santa Claus, on his view, is a genuine individual that simply lacks the property of existence. Most ontologists disagree, treating existence not as a feature of individuals at all but as a property of properties.
Existence is the state of being real, as opposed to nonbeing. The English word arrived in the late 14th century through Old French from medieval Latin roots meaning to stand forth or to arise. Philosophers often pair it with essence: essence is what a thing is, its defining qualities, and can be grasped without knowing whether the thing exists at all. The study of existence belongs to ontology, a branch of metaphysics.
On the orthodox view, saying lions exist means the property of being a lion is instantiated by at least one creature. Frege held that this general existence is more basic than the singular existence of a particular individual. Henry S. Leonard insisted a property exists only if something actually has it; Nicholas Rescher disagreed. The Japanese ontologist Takashi Yagisawa treats reality as the deeper notion and existence as a relation linking an entity to the world it inhabits.
Ontologists also sort kinds of existence. Rocks, plants and people are concrete, located in space and time and able to affect one another, as when a growing root cracks stone. Numbers and sets are abstract, and here opinion divides: realists in the tradition of Plato grant them independent existence, while anti-realists deny it. Telephones and flowers exist contingently, since they could have failed to exist, whereas a necessary being could not fail to exist.
Whether anything exists necessarily is an open question. Avicenna and Thomas Aquinas held that God does, serving as the explanatory ground of the cosmos, and Baruch Spinoza identified God with the world itself. Some thinkers go further and allow degrees of existence. The concept already surfaces in Presocratic Greek philosophy, in Hindu and Buddhist thought in ancient India, and in Daoism in ancient China.
Source: Existence
