The authors contend that most contemporary logic textbooks fail the average student because they emphasize the evaluation of arguments over their clarification, assuming that the student already understands what motivations underlie logic.

Most recent writers of informal logic texts draw a distinction between "linked" and "convergent" arguments. According to its inventor, Stephen Thomas, the distinction is of the utmost importance; it "seems crucial to the analysis and evaluation of reasoning in natural language." I argue that the distinction has not been drawn in any way that makes it both clear and of any real originality or importance. Many formulations are obscure or conceptually incoherent. One formulation of the distinction does seem tolerably clear (...) and I develop another, but neither promises to make it matter much. We can well do without it. (shrink)

We perceive relevance by virtue of inference habits, which may be expressed as Pierce's leading principles or as Toulmin's warrants. Hence relevance in a descriptive sense is a ternary relation between two statements and a set of inference rules. For a normative sense, the warrants must be properly backed. Different types of warrant to empirical generalizations, we introduce L.J. Cohen's notion of inductive support. A to empirical generalizations, we introduce L.J. Cohen's notion of inductive support. A generalization H is supported (...) by evidence E to degree i/in iff E indicates that H passes canonical test i, where there are n canonical tests. In a canonical test, one or more relevant variables, factors which may falsify H, are varied. H passes a test if it is not falsified. The tests are cumulative. Degree of support is relative to the canonical test, and may be modeled as relative to a point in a dialectical situation. A value of a variable at which H is falsified is a rebutting value. A is normatively relevant to B with respect to W iff sup[associated generalization(W), E] = i/n and for j > i, there is a presumption that the values of j are non-rebuting. (shrink)

"A sequel to Pollock's How to Build a Person, this volume builds upon that theoretical groundwork for the implementation of rationality through artificial ...

Ethics and jurisprudence are liable to the remark in common with logic. Almost every writer having taken a different view of some of the particulars which ...

How are dependent (or linked) premises to be distinguished from independent (or convergent) premises? Deductive validity, sometimes proposed as a necessary condition for depende'nce, cannot be, for the premises of both inductive and deductive but invalid arguments can be dependent. The question is really this: When do multiple premises for a certain conclusion fonn one argument for that conclusion and when do they form multiple arguments? Answer: Premises are dependent when the evidence they offer for their conclusion is more than (...) the ordinary sum of their probabilities. Ordinary sums are defined in the paper. (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)

Chapter The Need for a Theory of Argument Structure. THE STANDARD APPROACH The approach to argument diagramming which we call standard was originated, ...

This is a new release of the original 1949 edition.

The Aims of the Book -/- 1. To improve your skill in analyzing and evaluating arguments and presentations of the kind you find in everyday discourse (news media, discussions, advertisements), textbooks, and lectures. 2. To improve your skill in presenting arguments, reports and instructions clearly and persuasively. 3. To improve your critical instincts, that is, your immediate judgments of your attitudes toward the communications and behavior of others and yourself, so that you consistently approach them with the standards of reason (...) and the attitude of reasonableness. 4. To improve your knowledge about the facts and arguments relevant to a large number of important contemporary issues in politics, education, ethics, and several practical fields. -/- These are practical aims but not narrow practical aims: the third one, in particular, is very far-reaching and requires a whole shift of values for most of us. So this is intended to be a powerful, as well as practical, book using practical, everyday examples of the kind that a citizen, especially a citizen-student, runs into all the time. -/- The text starts with a short discussion of reasoning itself, then explores the details of this approach, and then gets down to practical procedures for improving one's reasoning skills. The discussions and examples always begin at a rather elementary level, but they get into harder material fairly quickly. If you are, or are hoping to be, a teacher or a lawyer, a scientist or an executive, what you learn here will be professional skills for you—vital professional skills. But for any citizen, they are also essential skills. (shrink)

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

There was a long tradition in philosophy according to which good reasoning had to be deductively valid. However, that tradition began to be questioned in the 1960’s, and is now thoroughly discredited. What caused its downfall was the recognition that many familiar kinds of reasoning are not deductively valid, but clearly confer justification on their conclusions. Here are some simple examples.

He further argues that it is necessary to rethink traditional conceptions of argument, and to find a position that avoids the limitations of both the highly abstract approach of formal logic and the highly contextualized approaches of rhetoric and communication theory.".

Many in the informal logic tradition distinguish convergent from linked argument structure. The pragma-dialectical tradition distinguishes multiple from co-ordinatively compound argumentation. Although these two distinctions may appear to coincide, constituting only a terminological difference, we argue that they are distinct, indeed expressing different disciplinary perspectives on argumentation. From a logical point of view, where the primary evaluative issue concerns sufficient strength of support, the unit of analysis is the individual argument, the particular premises put forward to support a given conclusion. (...) Structure is internal to this unit. From a dialectical point of view, where the focus concerns how well a critical discussion comes to a reasoned conclusion of some disputed question, the argumentation need not constitute a single unit of argument. The unit of dialectical analysis will be the entire argumentation made up of these several arguments. The multiple/co-ordinatively compound distinction is dialectical, while the linked/convergent distinction is logical. Keeping these two pairs of distinctions separate allows us to see certain attempts to characterize convergent versus linked arguments as rather characterizing multiple versus co-ordinatively compound arguments, in particular attempts of Thomas, Nolt, and Yanal, and to resolve straightforwardly conflicts, tensions, or anomalies in their accounts. Walton's preferred Suspension/Insufficient Proof test to identify linked argument structure correctly identifies co-ordinatively compound structure. His objection to using the concept of relevance to explicate the distinction between linked and convergent structure within co-ordinatively compound argumentation can be met through explicating relevance in terms of inference licenses. His counterexample to the Suspension/No Support test for identifying linked structure which this approach supports can itself be straightforwardly dealt with when the test is explicated through inference licenses. (shrink)

In his The Uses of Argument (Cambridge University Press, 1958), S. Toulmin presents serious charges against ordinary logical theory, e.g., that it does not distinguish between analytic or formally valid or conclusive or warrant-using arguments, that the distinction between premises and conclusion is a bad oversimplification, that "major premise" conceals the distinction between inference-warrant and inference-backings, that logicians have been mistakenly working under an ideal of geometrical form. The paper argues that none of the charges is proven, that most of (...) them cannot be proven, that Toulmin's new logic is at best only vaguely hinted at and that his suggestions are positively obscure or mistaken. (shrink)

There are many radically different ways of understanding the distinction between linked and convergent arguments. This paper provides a generic model which enables one to articulate in a rigorous manner the important differences as well as the underlying similarities that exist between competing proposals. In addition, the paper offers a TRUE (Type Reduction Upon Elimination) test for distinguishing linked from convergent arguments which best captures the informal intuition that linked arguments are especially vulnerable to local criticisms pertaining to premise acceptability.

tational background of dialectic: the structure of formal disputation. Formal disputation Perhaps the clearest, and surely historically the most prominent, ...

In many actual arguments, the conclusion seems intuitively to follow from the premisses, even though we cannot show that it follows logically. The traditional approach to evaluating such arguments is to suppose that they have an unstated premiss whose explicit addition will produce an argument where the conclusion does follow logically. But there are good reasons for doubting that people so frequently leave the premisses of their arguments unstated. The inclination to suppose that they do stems from the belief that (...) the only way in which an argument's conclusion can follow definitely from its premisses is to follow logically. I argue that this belief is mistaken. I propose a revision of the current generic conception of logical consequence, and its variant specifications, to avoid the paradoxes of strict implication. The revised conception can then be naturally extended to include also what we might call 'enthymematic consequence'. This concept is a kind of consequence, whose properties merit investigation. (shrink)

A generation before Beardsley, legal scholar John Henry Wigmore invented a scheme for representing arguments in a tree diagram, aimed to help advocates analyze the proof of facts at trial. In this essay, I describe Wigmore's "Chart Method" and trace its origin and influence. Wigmore, I argue, contributes to contemporary theory in two ways. His rhetorical approach to diagramming provides a novel perspective on problems about the theory of reasoning, premise adequacy, and dialectical obligations. Further, he advances a novel solution (...) to the problem of assessing argument quality by representing the strength of argument in meeting objections. (shrink)

Sometimes logical support for a conclusion is provided exclusively by premises which are independently relevant to that conclusion. At other times, support is provided exclusively by independently irrelevant premises. On still other occasions, relevant and irrelevant premises may collectively offer a distinctive pattern of support. This paper provides a rigorous account of some of these differences in terms of a tripartite classification of convergent, linked and hybrid arguments. These various arguments are defined, diagrammed, and some of their logical properties are (...) explored. (shrink)

In previous work I argued against (i) the likelihood of finding a theoretically sound foundation for the linked/convergent distinction and (ii) the utility of the distinction even if a sound theoretical basis could be found. Here I subject Douglas Walton’s comprehensive discussion of the linked/convergent distinction found in Argument Structure: A Pragmatic Theory to careful scrutiny and argue that at best Walton’s theory remains incomplete and that attempts to fill out the details will run afoul of at least one of (...) the problems adduced above—i.e., result in either a theoretically unsound distinction or a theoretically sound, but unnecessary distinction. (shrink)

This volume contains 12 papers addressed to researchers and advanced students in informal logic and related fields, such as argumentation, formal logic, and communications. Among the issues discussed are attempts to rethink the nature of argument and of inference, the role of dialectical context, and the standards for evaluating inferences, and to shed light on the interfaces between informal logic and argumentation theory, rhetoric, formal logic and cognitive psychology.