John Anthony Blair

In this overview article, we first explain what we take informal logic to be, discussing misconceptions and distinguishing our conception of it from competing ones; second, we briefly catalogue recent informal logic research, under 14 headings; third, we suggest four broad areas of problems and questions for future research; fourth, we describe current scholarly resources for informal logic; fifth, we discuss three implications of informal logic for philosophy in particular, and take note ofpractical consequences of a more general sort.

In Jonathan Adler argued that conductive arguments, as they are commonly characterized, are impossible—that no such argument can exist. This striking contention threatens to undermine a topic of argumentation theory originated by Trudy Govier based on Carl Wellman and revisited by the papers in “Conductive argument, An overlooked type of defeasible reasoning”. I here argue that Adler’s dismissal of conductive arguments relies on a misreading of the term ‘non-conclusive’ used in the characterization of this type of reasoning and argument, and that as a result, his refutation fails. However, Adler’s critique raises other questions about conductive arguments that have to be answered.

In Logical Self-Defense, Johnson and I introduced the criteria of acceptability, relevance and sufficiency as appropriate for the evaluation of arguments in the sense of reasons offered in support of a claim. These three criteria have been widely adopted, but each has been subjected to a number of criticisms; and also 30 years of research have intervened. How do these criteria stand up today? In this paper I argue that they still have a place in argument analysis and evaluation, but in much-modified roles.

Informal logic began in the 1970s as a critique of then-current theoretical assumptions in the teaching of argument analysis and evaluation in philosophy departments in the U.S. and Canada. The last 35 years have seen significant developments in informal logic and critical thinking theory. The paper is a pilot study of the influence of these advances in theory on what is taught in courses on argument analysis and critical thinking in U.S. and Canadian philosophy departments. Its finding, provisional and much-qualified, is that the theoretical developments and refinements have had limited impact on instruction in leading philosophy departments.

I argue that argumentation is not to be identified with (attempted) rational persuasion, because although rational persuasion appears to consist of arguments, some uses of arguments are not attempts at rational persuasion. However, the use of arguments in argumentative communication to try to persuade is one kind of attempt at rational persuasion. What makes it rational is that its informing ideal is to persuade on the basis of adequate grounds, grounds that make it reasonable and rational to accept the claim at issue.

The question, “What norms are appropriate for the evaluation of the probative merits of visual arguments?” underlies the investigation of this paper. The notions of argument and of multimodal visual argument employed in the study are explained. Then four multimodal visual arguments are analyzed and their probative merits assessed. It turns out to be possible to judge these qualities using the same criteria that apply to verbally expressed arguments. Since the sample is small and not claimed to be representative, this finding can at best be regarded as suggestive for the probative assessment of multimodal visual arguments in general.