In logic the universal quantifier is a quantifier that says that the following proposition applies to all elements of the universe of discourse. An example that uses this quantifier would be the proposition "All men are mortal". Usually, a turned A (∀) is used to denote the universal quantifier, "for all x" is written as either "∀x", "∀(x)".
Propositions can be falsified. To falsify a proposition which contains a universal quantifier, it is sufficient to find one element of the universe of discourse where the proposition is false.