Principles and Examples of Plausible Reasoning and Propositional Plausible Logic

TL;DR

This paper introduces Propositional Plausible Logic (PPL), a non-numeric non-monotonic logic designed to formalize plausible reasoning without quantifying uncertainty, and demonstrates its principles and applications.

Contribution

It presents a comprehensive set of principles for plausible reasoning and introduces PPL, the first non-numeric non-monotonic logic satisfying these principles and correctly handling key examples.

Findings

PPL satisfies all proposed principles of plausible reasoning.

PPL correctly reasons with important illustrative examples.

Several theoretical properties of PPL are proved.

Abstract

Plausible reasoning concerns situations whose inherent lack of precision is not quantified; that is, there are no degrees or levels of precision, and hence no use of numbers like probabilities. A hopefully comprehensive set of principles that clarifies what it means for a formal logic to do plausible reasoning is presented. A new propositional logic, called Propositional Plausible Logic (PPL), is defined and applied to some important examples. PPL is the only non-numeric non-monotonic logic we know of that satisfies all the principles and correctly reasons with all the examples. Some important results about PPL are proved.