Enthymemes, Argumentation Schemes and Topics

This paper argues for a reinterpretation of Aristotle’s concept of an enthymeme and also his wider informal logic in terms of arguments that are defeasible. They are represented by forms of argument that are called argumentation schemes, considered to be similar to forms of argument found in deductive logic, but different from the foregoing in virtue of their being defeasible. Indeed, the most interesting schemes have been put forward as a helpful way of characterizing structures of human reasoning that have proved troublesome to model deductively. The paper sheds new light on Aristotle’s topics and how to define ‘enthymeme’. If the traditional definition of an enthymeme in logic accepted for over two thousand years is a misnomer, the question is raised whether we ought to redefine it as a defeasible argumentations scheme or leave things as they are. Through recent studies in argumentation, the field of logic is expanding from only using deductive and inductive models of reasoning to a more inclusive approach also using semi-formal argumentation schemes. Defeasible schemes of this sort can be used to identify, analyze and evaluate arguments of the kind most commonly used in everyday conversational exchanges, as well as in practical areas like legal reasoning and medical diagnostic reasoning. These schemes seem similar to Aristotelian topics, common forms of argument that have been traditionally held to be important in both logic and rhetoric. However the history of topics has been convoluted. The notion of ‘topic’ has often been interpreted in different ways, and used for different purposes in the history of rhetoric and dialectic. To make the history of these subjects seem even more confusing, some have long contended that Aristotle also used the term ‘enthymeme’ in a way that refers not to an unstated assumption in argument, but to common forms of argument that we nowadays call argumentation schemes. It is our aim to clarify these confusions. Beginning with some examples of arguments described as enthymemes by Aristotle, this paper examines the relationship between these arguments