Plausible Reasoning and First-Order Plausible Logic

Computer Science > Artificial Intelligence [Submitted on 21 Apr 2026] Plausible Reasoning and First-Order Plausible Logic David Billington Defeasible statements are statements that are likely, or probable, or usually true, but may occasionally be false. Plausible reasoning makes conclusions from statements that are either facts or defeasible statements without using numbers. So there are no probabilities or suchlike involved. Seventeen principles of logics that do plausible reasoning are suggested and several important plausible reasoning examples are considered. There are 14 necessary principles and 3 desirable principles, one of which is not formally stated. A first-order logic, called Plausible Logic (PL), is defined that satisfies all but two of the desirable principles and reasons correctly with all the examples. As far as we are aware, this is the only such logic. PL has 8 reasoning algorithms because, from a given plausible reasoning situation, there are different sensible conclusions. This article is a condensation of my book `Plausible Reasoning and Plausible Logic' (PRPL), which is to be submitted. Each section of this article corresponds to a chapter in PRPL, and vice versa. The proofs of all the results are in PRPL, so they are omitted in this article. Comments: 28 pages. arXiv admin note: text overlap with arXiv:1703.01697 Subjects: Artificial Intelligence (cs.AI); Logic in Computer Science (cs.LO) MSC classes: 03B60 ACM classes: F.4.1 Cite as: arXiv:2604.19036 [cs.AI]   (or arXiv:2604.19036v1 [cs.AI] for this version)   https://doi.org/10.48550/arXiv.2604.19036 Focus to learn more Submission history From: David Billington [view email] [v1] Tue, 21 Apr 2026 03:39:56 UTC (55 KB) Access Paper: HTML (experimental) view license Current browse context: cs.AI < prev   |   next > new | recent | 2026-04 Change to browse by: cs cs.LO References & Citations NASA ADS Google Scholar Semantic Scholar Export BibTeX Citation Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer (What is the Explorer?) Connected Papers Toggle Connected Papers (What is Connected Papers?) Litmaps Toggle Litmaps (What is Litmaps?) scite.ai Toggle scite Smart Citations (What are Smart Citations?) Code, Data, Media Demos Related Papers About arXivLabs Which authors of this paper are endorsers? | Disable MathJax (What is MathJax?)