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".
Famous quotes containing the word existence:
“I create my social existence by earning and spending.”
—Mason Cooley (b. 1927)
“There are moments of existence when time and space are more profound, and the awareness of existence is immensely heightened.”
—Charles Baudelaire (18211867)
“Creation destroys as it goes, throws down one tree for the rise of another. But ideal mankind would abolish death, multiply itself million upon million, rear up city upon city, save every parasite alive, until the accumulation of mere existence is swollen to a horror.”
—D.H. (David Herbert)