Existence
Existence is the state of having being or reality in contrast to nonexistence and nonbeing. Existence is often contrasted with essence: the essence of an entity is its essential features or qualities, which can be understood even if one does not know whether the entity exists.
Ontology is the philosophical discipline studying the nature and types of existence. Singular existence is the existence of individual entities while general existence refers to the existence of concepts or universals. Entities present in space and time have concrete existence in contrast to abstract entities, like numbers and sets. Other distinctions are between possible, contingent, and necessary existence and between physical and mental existence. The common view is that an entity either exists or not with nothing in between, but some philosophers say that there are degrees of existence, meaning that some entities exist to a higher degree than others.
The orthodox position in ontology is that existence is a second-order property, or a property of properties. For example, to say that lions exist means that the property of being a lion is possessed by an entity. A different view sees existence as a first-order property, or a property of individuals, meaning existence is similar to other properties of individuals, like color and shape. Alexius Meinong and his followers accept this idea and say that not all individuals have this property; they state that there are some individuals, such as Santa Claus, that do not exist. Universalists reject this view; they see existence as a universal property of every individual.
The concept of existence has been discussed throughout the history of philosophy and already played a role in ancient philosophy, including Presocratic philosophy in Ancient Greece, Hindu and Buddhist philosophy in Ancient India, and Daoist philosophy in ancient China. It is relevant to fields such as logic, mathematics, epistemology, philosophy of mind, philosophy of language, and existentialism.
Definition and related terms
Existence is the state of being real or participating in reality. Existence sets real entities apart from imaginary ones, and can refer both to individual entities or to the totality of reality. The word "existence" entered the English language in the late 14th century from old French and has its roots in the medieval Latin term existere, which means "to stand forth", "to appear", and "to arise". Existence is studied by the subdiscipline of metaphysics known as ontology.The terms "being", "reality", and "actuality" are often used as synonyms of "existence", but the exact definition of existence and its connection to these terms is disputed. According to metaphysician Alexius Meinong, all entities have being but not all entities have existence. He argues merely possible objects like Santa Claus have being but lack existence. Ontologist Takashi Yagisawa contrasts existence with reality; he sees "reality" as the more-fundamental term because it equally characterizes all entities and defines existence as a relative term that connects an entity to the world it inhabits. According to philosopher Gottlob Frege, actuality is narrower than existence because only actual entities can produce and undergo changes, in contrast to non-actual existing entities like numbers and sets. According to some philosophers, like Edmund Husserl, existence is an elementary concept, meaning it cannot be defined in other terms without involving circularity. This would imply characterizing existence or talking about its nature in a non-trivial manner may be difficult or impossible.
Disputes about the nature of existence are reflected in the distinction between thin and thick concepts of existence. Thin concepts of existence understand existence as a logical property that every existing thing shares; they do not include any substantial content about the metaphysical implications of having existence. According to one view, existence is the same as the logical property of self-identity. This view articulates a thin concept of existence because it merely states what exists is identical to itself without discussing any substantial characteristics of the nature of existence. Thick concepts of existence encompass a metaphysical analysis of what it means that something exists and what essential features existence implies. According to one proposal, to exist is to be present in space and time, and to have effects on other things. This definition is controversial because it implies abstract objects such as numbers do not exist. Philosopher George Berkeley gave a different thick concept of existence; he stated: "to be is to be perceived", meaning all existence is mental.
Existence contrasts with nonexistence, a lack of reality. Whether objects can be divided into existent and nonexistent objects is a subject of controversy. This distinction is sometimes used to explain how it is possible to think of fictional objects like dragons and unicorns but the concept of nonexistent objects is not generally accepted; some philosophers say the concept is contradictory. Closely related contrasting terms are nothingness and nonbeing. Existence is commonly associated with mind-independent reality but this position is not universally accepted because there could also be forms of mind-dependent existence, such as the existence of an idea inside a person's mind. According to some idealists, this may apply to all of reality.
Another contrast is made between existence and essence. Essence refers to the intrinsic nature or defining qualities of an entity. The essence of something determines what kind of entity it is and how it differs from other kinds of entities. Essence corresponds to what an entity is, while existence corresponds to the fact that it is. For instance, it is possible to understand what an object is and grasp its nature even if one does not know whether this object exists. According to some philosophers, there is a difference between entities and the fundamental characteristics that make them the entities they are. Martin Heidegger introduced this concept; he calls it the ontological difference and contrasts individual beings with being. According to his response to the question of being, being is not an entity but the background context that makes all individual entities intelligible.
Types of existing entities
Many discussions of the types of existing entities revolve around the definitions of different types, the existence or nonexistence of entities of a specific type, the way entities of different types are related to each other, and whether some types are more fundamental than others. Examples are the existence or nonexistence of souls; whether there are abstract, fictional, and universal entities; and the existence or nonexistence of possible worlds and objects besides the actual world. These discussions cover the topics of the basic stuff or constituents underlying all reality and the most general features of entities.Singular and general
There is a distinction between singular existence and general existence. Singular existence is the existence of individual entities. For example, the sentence "Angela Merkel exists" expresses the existence of one particular person. General existence pertains to general concepts, properties, or universals. For instance, the sentence "politicians exist" states the general term "politician" has instances without referring to a particular politician.Singular and general existence are closely related to each other, and some philosophers have tried to explain one as a special case of the other. For example, according to Frege, general existence is more basic than singular existence. One argument in favor of this position is that singular existence can be expressed in terms of general existence. For instance, the sentence "Angela Merkel exists" can be expressed as "entities that are identical to Angela Merkel exist", where the expression "being identical to Angela Merkel" is understood as a general term. Philosopher Willard Van Orman Quine defends a different position by giving primacy to singular existence and arguing that general existence can be expressed in terms of singular existence.
A related question is whether there can be general existence without singular existence. According to philosopher Henry S. Leonard, a property only has general existence if there is at least one actual object that instantiates it. Philosopher Nicholas Rescher, by contrast, states that properties can exist if they have no actual instances, like the property of "being a unicorn". This question has a long philosophical tradition in relation to the existence of universals. According to Platonists, universals have general existence as Platonic forms independently of the particulars that exemplify them. According to this view, the universal of redness exists independently of the existence or nonexistence of red objects. Aristotelianism also accepts the existence of universals but says their existence depends on particulars that instantiate them and that they are unable to exist by themselves. According to this view, a universal that is not present in the space and time does not exist. According to nominalists, only particulars have existence and universals do not exist.
Concrete and abstract
There is an influential distinction in ontology between concrete and abstract objects. Many concrete objects, like rocks, plants, and other people, are encountered in everyday life. They exist in space and time. They have effects on each other, like when a rock falls on a plant and damages it, or a plant grows through rock and breaks it. Abstract objects, like numbers, sets, and types, have no location in space and time, and lack causal powers. The distinction between concrete objects and abstract objects is sometimes treated as the most-general division of being.The existence of concrete objects is widely agreed upon but opinions about abstract objects are divided. Realists such as Plato accept the idea that abstract objects have independent existence. Some realists say abstract objects have the same mode of existence as concrete objects; according to others, they exist in a different way. Anti-realists state that abstract objects do not exist, a view that is often combined with the idea that existence requires a location in space and time or the ability to causally interact.