Existence

Existence is commonly held to be that which objectively persists independent of one's presence.

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, (for instance: "Does the stellar structure UDFj-39546284 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 is the branch of philosophy concerned with the nature and scope of knowledge; it is also referred to as "theory of knowledge". Usually, it is limited to the study of the classical components of justified true belief. Epistemology also investigates how knowledge can be taught or acquired, and the conditions and extent to which any given subject or entity can be known.