Existence has been variously defined by sources. In common usage, it is the world one is aware or conscious of through one's senses, and that persists independently in one's absence. Other definitions describe it as everything that 'is', or more simply, everything. Some define it to be everything that most people believe in. Aristotle relates the concept to causality.

Ontology is the philosophical study of the nature of being, existence or reality in general, as well as of the basic categories of being and their relations. Traditionally listed as a part of the major branch of philosophy known as metaphysics, ontology deals with questions concerning what entities exist or can be said to exist, and how such entities can be grouped, related within a hierarchy, and subdivided according to similarities and differences. A lively debate continues about the existence of God.

Epistemology studies criteria of truth, defining "primary truths" inherently accepted in the investigation of knowledge. The first is existence. It is inherent in every analysis. Its self-evident, a priori nature cannot be consistently doubted, since a person objecting to existence according to some standard of proof must implicitly accept the standard's existence as a premise.

Materialism holds that the only thing that exists is matter, that all things are composed of material, and all phenomena (including consciousness) are the result of material interactions.

Life is a characteristic that distinguishes objects that have self-sustaining biological processes from those that do not – either because such functions have ceased (death), or else because they lack such functions and are classified as "inanimate".

Read more about Existence:  Etymology, Historical Conceptions, Predicative Nature, Modern Approaches, Dharmic "middle Way" View

Famous quotes containing the word existence:

    We know then the existence and nature of the finite, because we also are finite and have extension. We know the existence of the infinite and are ignorant of its nature, because it has extension like us, but not limits like us. But we know neither the existence nor the nature of God, because he has neither extension nor limits.
    Blaise Pascal (1623–1662)

    Suppose that humans happen to be so constructed that they desire the opportunity for freely undertaken productive work. Suppose that they want to be free from the meddling of technocrats and commissars, bankers and tycoons, mad bombers who engage in psychological tests of will with peasants defending their homes, behavioral scientists who can’t tell a pigeon from a poet, or anyone else who tries to wish freedom and dignity out of existence or beat them into oblivion.
    Noam Chomsky (b. 1928)

    ... my whole existence is governed by abstract ideas.... the ideal must be preserved regardless of fact.
    Mary Corinna Putnam (1842–1906)