New Plausible Logic Framework for Defeasible Reasoning Without Probabilities
A new first-order logic system called Plausible Logic (PL) has been introduced for reasoning with defeasible statements—propositions that are typically true but may have exceptions—without relying on numerical probabilities. The framework operates solely with facts and defeasible statements, avoiding quantitative measures entirely. Seventeen logical principles guide this approach, comprising fourteen essential rules and three desirable ones, with one of the latter not formally articulated. PL satisfies all but two of these desirable principles and correctly handles multiple important examples of plausible reasoning, making it the only known logic of its kind to achieve this. The system includes eight distinct reasoning algorithms because different sensible conclusions can emerge from the same plausible reasoning scenario. This work represents a condensed version of the author's book 'Plausible Reasoning and Plausible Logic'.
Key facts
- Defeasible statements are likely or usually true but can be false
- Plausible reasoning uses facts and defeasible statements without numbers
- Seventeen principles of logic are suggested for plausible reasoning
- Fourteen principles are necessary, three are desirable
- One desirable principle is not formally stated
- First-order Plausible Logic (PL) satisfies all but two desirable principles
- PL reasons correctly with all considered examples
- PL has eight reasoning algorithms for different sensible conclusions
Entities
Institutions
- arXiv