Practice question · Multiple choice
Modal logic models necessity across possible worlds rather than degrees of belief. What follows from treating possibility this way rather than as epistemic uncertainty?
Hints
- Does the existence of an accessible world depend on what an observer knows?
- How does formal truth in a non-actual world differ from subjective doubt?
Show the answer
C. A claim known to be false remains possible if consistent with a world
Why
Modal semantics evaluates claims across accessible model worlds, not epistemic states or probability distributions. Treating possibility as uncertainty confuses formal accessibility with subjective ignorance, which breaks down when analysing counterfactual alternatives.
Practise Modal Logic: Necessity and Possibility
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More questions on Modal Logic: Necessity and Possibility
- Why must deontic logic reject the principle that whatever is necessary is actually true?
- The possibility operator means that a sentence is probably true.
- Arrange these modal systems in order of increasing strength, from the weakest constraints on accessibility to…
- Match each accessibility constraint to the principle it validates.
- Sort each claim by whether it concerns necessity or possibility.