This paper is an exercise in intellectual history, an attempt to understand how a specific term—”informal logic”— came to be interpreted in so many different ways. I trace the emergence and development of “informal logic” to help explain the many different meanings, how they emerged and how they are related. This paper is also, to some degree, an account of a movement that developed outside the mainstream of philosophy, whose origins lie in a desire to make logic useful (echoing Dewey).

We present a formal, mathematical model of argument structure and evaluation, taking seriously the procedural and dialogical aspects of argumentation. The model applies proof standards to determine the acceptability of statements on an issue-by-issue basis. The model uses different types of premises (ordinary premises, assumptions and exceptions) and information about the dialectical status of statements (stated, questioned, accepted or rejected) to allow the burden of proof to be allocated to the proponent or the respondent, as appropriate, for each premise separately. (...) Our approach allows the burden of proof for a premise to be assigned to a different party than the one who has the burden of proving the conclusion of the argument, and also to change the burden of proof or applicable proof standard as the dialogue progresses from stage to stage. Useful for modeling legal dialogues, the burden of production and burden of persuasion can be handled separately, with a different responsible party and applicable proof standard for each. Carneades enables critical questions of argumentation schemes to be modeled as additional premises, using premise types to capture the varying effect on the burden of proof of different kinds of questions. (shrink)

An abstract framework for structured arguments is presented, which instantiates Dung's ('On the Acceptability of Arguments and its Fundamental Role in Nonmonotonic Reasoning, Logic Programming, and n- Person Games', Artificial Intelligence , 77, 321-357) abstract argumentation frameworks. Arguments are defined as inference trees formed by applying two kinds of inference rules: strict and defeasible rules. This naturally leads to three ways of attacking an argument: attacking a premise, attacking a conclusion and attacking an inference. To resolve such attacks, preferences may (...) be used, which leads to three corresponding kinds of defeat: undermining, rebutting and undercutting defeats. The nature of the inference rules, the structure of the logical language on which they operate and the origin of the preferences are, apart from some basic assumptions, left unspecified. The resulting framework integrates work of Pollock, Vreeswijk and others on the structure of arguments and the nature of defeat and extends it in several respects. Various rationality postulates are proved to be satisfied by the framework, and several existing approaches are proved to be a special case of the framework, including assumption-based argumentation and DefLog. (shrink)

Mr. Wellman’s highly original contribution to the relatively new field of justification in ethics consists of characterizing the different ways in which ethical statements can be challenged and showing how each sort of challenge can be met by an appropriate response, enabling reasonable men to appropriately discuss or reflect on ethical issues. In developing his unique, systematic, methodology of ethics, Mr. Wellman has, first, rigorously reviewed and refuted the main arguments for the view of the nature of all reasoning as (...) deductive and, second, convincingly presented arguments for the existence of nondeductive evidences in ethics. Mr. Wellman’s broad definition of reasoning and his rejection of the identification of justification with reasoning reveals new dimensions of justification which will have wide implications in other areas of human speculation. (shrink)

Mr. Wellman’s highly original contribution to the relatively new field of justification in ethics consists of characterizing the different ways in which ethical statements can be challenged and showing how each sort of challenge can be met by an appropriate response, enabling reasonable men to appropriately discuss or reflect on ethical issues. In developing his unique, systematic, methodology of ethics, Mr. Wellman has, first, rigorously reviewed and refuted the main arguments for the view of the nature of all reasoning as (...) deductive and, second, convincingly presented arguments for the existence of nondeductive evidences in ethics. Mr. Wellman’s broad definition of reasoning and his rejection of the identification of justification with reasoning reveals new dimensions of justification which will have wide implications in other areas of human speculation. (shrink)

Argument invention is a method that can be used to help an arguer find arguments that could be used to prove a claim he needs to defend. The aim of this paper is to show how argumentation systems recently developed in artificial intelligence can be applied to the task of argument invention. One such system called Carneades is featured. Carneades can be used to analyze arguments, evaluate arguments, to make an argument diagram, and to construct arguments from a database. Using (...) some simple examples, the paper explains how Carneades works as a system of argument invention. (shrink)

William Baird collection in Social Sciences is the gift of the Estate of William Cameron Baird.

The aim of the paper is to advance the theory of argument or inference schemes by suggesting answers to questions raised by Walton's Argumentation Schemes for Presumptive Reasoning (1996), specifically on: the relation between argument and reasoning; distinguishing deductive from presumptive schemes, the origin of schemes and the probative force of their use; and the motivation and justification for their associated critical questions.

This paper deals with what has been called "ars inveniendi" (’art of finding‘) in antiquity, medieval and early modern times. A survey of different techniques of finding tenable and relevant arguments is presented (among them, the Topical tradition, Status theory, Debate theory, Encyclopedic systems, Creativity techniques). Their advantages and disadvantages are critically compared. It is suggested that a mixture of strategies of finding arguments should be used. Finally, a few remarks showing the relationship beween the strategies of finding arguments and (...) creativity in general are given. (shrink)

Vol. presents a method for critically evaluating relevance in arguments based on case studies & a new relevance theory incorporating techniques of argumentation theory, logic & artificiaI intelligence. For scholars/students in argumentation & rhetoric.