Individual km#modal_logic__intensional_logic__intensionallogic  sentences are qualified by modalities such as possibly and necessarily; both "Bush is president" and "2+2=4" are true, yet "Necessarily, Bush is president" is false, while "Necessarily, 2+2=4" is true
  >part:  deontic_logic  epistemic_logic  temporal_logic  conditional_logic
  url:  http://en.wikipedia.org/wiki/Modal_logic  http://plato.stanford.edu/entries/logic-modal/
  >part of:  formal_logic
     >part of:  logic.philosophy  the branch of philosophy that analyzes inference
        >part of:  philosophy  the rational investigation of questions about existence and knowledge and ethics

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