Philosophy Dictionary of Arguments  
 
Modal logic: the modal logic is an extension of classical logic to systems in which possibility and necessity can also be expressed. Different approaches use operators to express "necessary" and "possible", which, depending on the placement within formulas, can let claims of different strengths win. E.g. there is an object which necessarily has the property F/it is necessary that there is an object with the property F. The introduction of possible worlds makes quantification possible for expressing possibility (There is at least one world in which ...) and necessity (For all worlds is valid ...). See also operators, quantifier, completion, range, possible worlds. _____________ Annotation: The above characterizations of concepts are neither definitions nor exhausting presentations of problems related to them. Instead, they are intended to give a short introduction to the contributions below. – Lexicon of Arguments.  
Author  Item  More concepts for author  

Bigelow, John  Modal Logic  Bigelow, John  
Chisholm, Roderick  Modal Logic  Chisholm, Roderick  
Field, Hartry  Modal Logic  Field, Hartry  
Geach, Peter T.  Modal Logic  Geach, Peter T.  
Hintikka, Jaakko  Modal Logic  Hintikka, Jaakko  
Kripke, Saul A.  Modal Logic  Kripke, Saul A.  
Lewis, David K.  Modal Logic  Lewis, David K.  
Quine, Willard Van Orman  Modal Logic  Quine, Willard Van Orman  
Stalnaker, Robert  Modal Logic  Stalnaker, Robert  
