In common usage, existence is the world of which we are aware through our senses, but in philosophy the word has a more specialized meaning, and is often contrasted with essence. Philosophers investigate questions such as “What exists?” “How do we know?” “To what extent are the senses a reliable guide to existence?” “What is the meaning, if any, of assertions of the existence of categories, ideas, and abstractions.”
The word “existence” comes from the Latin word existere meaning “to appear,” “to arise,” “to become,” or “to be,” but literally, it means “to stand out” (ex- being the Latin prefix for “out” added to the Latin verb stare, meaning “to stand”).
The word ‘exist’ is certainly a grammatical predicate, but philosophers have long disputed whether it is also a logical predicate. Some philosophers claim that it predicates something, and has the same meaning as ‘is real’, ‘has being’, ‘is found in reality’, ‘is in the real world’ and so on. Other philosophers deny that existence is logically a predicate, and claim that it is merely what is asserted by the etymologically distinct verb ‘is’, and that all statements containing the predicate ‘exists’ can be reduced to statements that do not use this predicate. For example, ‘A Four-leaved clover exists.’ can be rephrased as ‘There is a clover with four leaves.’
This philosophical question is an old one, and has been discussed and argued over by philosophers from Parmenides, Plato, Aristotle, through Avicenna, Aquinas, Scotus, Hume, Kant, Kierkegaard and many others.
In mathematical logic existence is a quantifier, the “existential quantifier”, symbolized by ∃, a backwards capital E. To symbolize “Four leaf clovers exist,” mathematicians would first define predicates, P(x) = “x is a clover” and Q(x) = “x has four leaves”, and then form the well-formed formula (∃x)(P(x) and Q(x))…
