Barcan formula

<math>\forall x \Box A \rightarrow \Box \forall x A</math>

In English, the statement reads, "'For all x, it is necessary that A', implies, 'It is necessary that for all x, A'". The formula tells us that if everything is quantifiable in all other worlds then it would have to be necessary that everything is quantifiable in our world as well.

The Barcan formula is used in S5[?] modal logic[?] of the Kripke System[?].

The Barcan formula has generated some controversy because some philosophers believe the formula violates the structure of the Kripke System.

Related formulas include the Converse Barcan formula[?], Buridian formula[?], and the Converse Buridian formula[?].

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