Search results
Results From The WOW.Com Content Network
Existential quantification is distinct from universal quantification ("for all"), which asserts that the property or relation holds for all members of the domain. [2] [3] Some sources use the term existentialization to refer to existential quantification. [4] Quantification in general is covered in the article on quantification (logic).
In symbolic logic, the universal quantifier symbol (a turned "A" in a sans-serif font, Unicode U+2200) is used to indicate universal quantification. It was first used in this way by Gerhard Gentzen in 1935, by analogy with Giuseppe Peano's (turned E) notation for existential quantification and the later use of Peano's notation by Bertrand Russell.
As a general rule, swapping two adjacent universal quantifiers with the same scope (or swapping two adjacent existential quantifiers with the same scope) doesn't change the meaning of the formula (see Example here), but swapping an existential quantifier and an adjacent universal quantifier may change its meaning.
This sort of quantification is known as uniqueness quantification or unique existential quantification, and is often denoted with the symbols "∃!" [ 2 ] or "∃ =1 ". For example, the formal statement
Quantifier symbols: ∀ for universal quantification, and ∃ for existential quantification; Logical connectives: ∧ for conjunction, ∨ for disjunction, → for implication, ↔ for biconditional, ¬ for negation. Some authors [11] use Cpq instead of → and Epq instead of ↔, especially in contexts where → is used for other purposes.
In formal semantics, existential closure is an operation which introduces existential quantification. It was first posited by Irene Heim in her 1982 dissertation, as part of her analysis of indefinites. In her formulation, existential closure is a form of unselective binding which binds any number of variables of any semantic type.
Existentialism asserts that people make decisions based on subjective meaning rather than pure rationality. The rejection of reason as the source of meaning is a common theme of existentialist thought, as is the focus on the anxiety and dread that we feel in the face of our own radical free will and our awareness of death.
In predicate logic, existential generalization [1] [2] (also known as existential introduction, ∃I) is a valid rule of inference that allows one to move from a specific statement, or one instance, to a quantified generalized statement, or existential proposition.