Editing Existential quantification (section)

===Notation===
In [[First-order logic|symbolic logic]], "∃" (a turned letter "[[E]]" in a [[sans-serif]] font, Unicode U+2203) is used to indicate existential quantification. For example, the notation <math>\exists{n}{\in}\mathbb{N}: n\times n=25</math> represents the (true) statement

:There exists some <math>n</math> in the set of [[natural number]]s such that <math>n\times n=25</math>.

The symbol's first usage is thought to be by [[Giuseppe Peano]] in ''[[Formulario mathematico]]'' (1896). Afterwards, [[Bertrand Russell]] popularised its use as the existential quantifier. Through his research in set theory, Peano also introduced the symbols <math>\cap</math> and <math>\cup</math> to respectively denote the intersection and union of sets.<ref name="Webb2018">{{cite book |author=Stephen Webb |title=Clash of Symbols |publisher=Springer Cham |year=2018 |isbn=978-3-319-71349-6 |doi=10.1007/978-3-319-71350-2 |url=http://link.springer.com/10.1007/978-3-319-71350-2|pages=210–211}}</ref>