Philosophy I / Modal Systems and Possible Worlds
Practice question · Match the pairs

Match each branch of modal logic to what its operators range over.

  • Alethic
  • Temporal
  • Epistemic
  • Deontic
  • Situations compatible with what is known
  • Situations in which all obligations are met
  • Ways the world could have been
  • Times, past and future
Hints
  1. Each branch reinterprets accessible worlds as a different kind of alternative.
  2. One of them ranges over ideal situations rather than genuine possibilities.
Show the answer
  • Alethic Ways the world could have been
  • Temporal Times, past and future
  • Epistemic Situations compatible with what is known
  • Deontic Situations in which all obligations are met
Why

The formal machinery is identical; only the interpretation of a "world" changes. Deontic worlds are ideal rather than possible, which is exactly why PP\Box P \rightarrow P fails there.

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