Non-monotonic Logic
Updated 2026-09-10
INTRODUCTION
English translation pending.
CORE DEFINITION
Non-monotonic logic is a family of formal logics that model and clarify defeasible reasoning. Reasoning is defeasible when the reasoner draws a conclusion while reserving the right to withdraw it on receiving further information; inductive generalization, inference to the best explanation, and inference from expert opinion are all of this kind. Adding premises can therefore remove conclusions.
SCAFFOLDING EFFECT
Reduce cognitive load
- Make default leaps: draw a conclusion from typical cases when information is incomplete rather than stalling. - Retract on exception: treat the conclusion as defeasible and keep room for revision. - Rank priorities: when rules conflict, use the reliability of the information to decide which inference survives.
Anchor fast decisions
Classical logic is monotonic: adding premises only adds conclusions. Commonsense reasoning is not, since from birds fly we infer that a particular bird flies and must retract that once we learn it is a penguin. Non-monotonic logic encodes this leap with default rules, exception conditions, and priority orderings: conclude by default first, then defeat the conclusion when higher-priority contrary information appears.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- plato.stanford.eduhttps://plato.stanford.edu/entries/logic-nonmonotonic/verified
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