|Barcan formula: claims that from the fact that it is possible that an object has a certain property it follows that this object exists. The formula is valid only in a few systems. See also modal logic.|
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Barcan-Formula/BF/Stalnaker : involves the interaction of the universal quantifier with the necessity operator : (BF ) " NF x ^ > N " x ^ F - converse: (CBF) N " F ^ x > " x ^ NF - Kripke 1963), its semantics showed that semantic assumptions are also needed. He showed a fallacy in the proofs that they supposedly deduced in which these assumptions were missing - it is valid if wuU , Du < Dw means if the subject matter of the accessible powo is a subset of the range of the output powo is - vice versa for the converse -> qualified converse of BF / Stalnaker : with existence adoption - ( QCBF ) N "x ^ F> " x ^ N ex > F) - existence predicate e: Ey ^ (x = y ) -
Barcan-Formula/qualified converse / Stalnaker : if in poss.wrld. w it is necessary that everything satisfies F, then everything must exist in w, F meet in any accessible poss.wrld. this individual exists - that is valid in our semantics but no theorem - because it is a variant of the invalid semantics - this is what we examine here.
Ways a World may be Oxford New York 2003