Applying Recent Argumentation Methods to Some Ancient Examples of Plausible Reasoning

Short Abstract: Eleven characteristics of plausible reasoning are specified by analyzing key examples of it recognized as important in ancient Greek skeptical philosophy using an AI model called the Carneades Argumentation System. In this paper, it is shown that there is a significant connection between the ancient recognition of plausible reasoning by the Greek skeptics and Sophists and the resurgence of the notion in recent work in argumentation theory and artificial intelligence. The aims of the paper are to analyze plausible reasoning and show that it has distinctive characteristics as a type of reasoning by examining some historically important paradigm examples and by applying modern tools of argument identification and analysis to them, including argument mapping tools and defeasible argumentation schemes. A special case in point is the Carneades Argumentation System (CAS), a formal mathematical model of argumentation and software visualization tool used in artificial Plausible reasoning was acknowledged as important in the ancient philosophy by the Sophists, who gave many good examples of its use (Tindale, 2010). In later Greek philosophy, Carneades, the head of the Third Academy, developed a theory of plausible reasoning to reply to the objection by the opponents of the Academics that Academic skepticism left no room for rational assent in the conduct of everyday deliberations. Although the skeptics deeply explored the limits of reason and its inability to establish fundamental truth, they have often been fallaciously criticized, ignored, and not taken seriously throughout the history of philosophy (Groarke, 1990, 4-5). This paper analyzes some ancient examples of plausible reasoning, most notably a very famous one attributed to Carneades, using modern argumentation methods. The first section situates plausible reasoning in a modern framework by showing how the classic example of defeasible reasoning based on perception represents a distinct kind of plausible reasoning that can be used to support a conclusion subject to critical questioning. Section 2 outlines two of the most famous examples of plausible reasoning that were familiar in ancient philosophy. Both examples are analyzed to show how they represent a distinctive kind of pro-contra argumentation based on certain common forms of argument, including argument from negative consequences and argument from evidence to a hypothesis. One of these examples shows how plausible reasoning is especially important for evidential legal argumentation of the kind that takes place in a trial setting. Section 3 outlines the theory of plausible reasoning attributed to the ancient skeptical philosopher …