Practice question · Sort into groups
Sort each claim by whether it concerns necessity or possibility.
Groups: Necessity · Possibility
- Could not have been otherwise
- True in at least one accessible world
- Might have been the case
- True in every accessible world
Hints
- Necessity quantifies universally and possibility existentially.
- The everyday phrasings track the formal semantics closely.
Show the answer
Necessity: True in every accessible world, Could not have been otherwise
Possibility: True in at least one accessible world, Might have been the case
Why
The formal contrast is universal versus existential quantification over worlds, and the ordinary phrasings track it well, "could not have been otherwise" really is truth in every accessible world.
Practise Modal Logic: Necessity and Possibility
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More questions on Modal Logic: Necessity and Possibility
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