In this paper, it is argued that the most fruitful approach to developing normative models of argument quality is one that combines the argumentation scheme approach with Bayesian argumentation. Three sample argumentation schemes from the literature are discussed: the argument from sign, the argument from expert opinion, and the appeal to popular opinion. Limitations of the scheme-based treatment of these argument forms are identified and it is shown how a Bayesian perspective may help to overcome these. At the same time, (...) the contributions of the standard scheme-based approach are highlighted, and it is argued that only a combination of the insights of different traditions will yield a complete normative theory of argument quality. (shrink)

semantic minimalism and moderte contextualism.

This paper combines various structures representing degrees of belief, degrees of disbelief, and degrees of non-belief (degrees of expectations) into a unified whole. The representation uses relations of comparative necessity and possibility, as well as non-probabilistic functions assigning numerical values of necessity and possibility. We define all-encompassing necessity structures which have weak expectations (mere hypotheses, guesses, conjectures, etc.) occupying the lowest ranks and very strong, ineradicable ('a priori') beliefs occupying the highest ranks. Structurally, there are no differences from the top (...) to the bottom. I argue that belief is a vague notion, and that thresholds for belief, if there are any, are context-dependent. (shrink)

The paper presents a ‘multiple agent’ logic where formulas are pairs of the form, made of a proposition and a subset of agents. The formula is intended to mean ‘ all agents in believe that is true’. The formal similarity of such formulas with those of possibilistic logic, where propositions are associated with certainty levels, is emphasised. However, the subsets of agents are organised in a Boolean lattice, while certainty levels belong to a totally ordered scale. The semantics of a (...) set of ‘multiple agent’ logic formulas is expressed by a mapping which associates a subset of agents with each interpretation. Soundness and completeness results are established. Then a joint extension of the multiple agent logic and possibilistic logic is outlined. In this extended logic, propositions are then associated with both sets of agents and certainty levels. A formula then expresses that ‘all agents in set believe that is true at least at some level’. The semantics is then given in terms of fuzzy sets of agents that find an interpretation more or less possible. A specific feature of possibilistic logic is that the inconsistency of a knowledge base is a matter of degree. The proposed setting enables us to distinguish between the global consistency of a set of agents and their individual consistency. In particular, given a set of multiple agent possibilistic formulas, one can compute the subset of agents that are individually consistent to some degree. (shrink)

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.

Various theories try to give accounts of how measures of this confidence do or ought to behave, both as far as the internal mental consistency of the agent as ...

Enthymemes are traditionally defined as arguments in which some elements are left unstated. It is an empirical fact that enthymemes are both enormously frequent and appropriately understood in everyday argumentation. Why is it so? We outline an answer that dispenses with the so called "principle of charity", which is the standard notion underlying most works on enthymemes. In contrast, we suggest that a different force drives enthymematic argumentation—namely, parsimony, i.e. the tendency to optimize resource consumption, in light of the agent's (...) goals. On this view, the frequent use of enthymemes does not indicate sub-optimal performance of arguers, requiring appeals to charity for their redemption. On the contrary, it is seen as a highly adaptive argumentation strategy, given the need of everyday reasoners to optimize their cognitive resources. Considerations of parsimony also affect enthymeme reconstruction, i.e. the process by which the interpreter makes sense of the speaker's enthymemes. Far from being driven by any pro-social cooperative instinct, interpretative efforts are aimed at extracting valuable information at reasonable costs from available sources. Thus, there is a tension between parsimony and charity, insofar as the former is a non-social constraint for self-regulation of one's behaviour, whereas the latter implies a pro-social attitude. We will argue that some versions of charity are untenable for enthymeme interpretation, while others are compatible with the view defended here, but still require parsimony to expose the ultimate reasons upon which a presumption of fair treatment in enthymeme reconstruction is founded. (shrink)

This paper highlights the difference between Lilian Bermejo-Luque’s account of warrants with the quite different accounts of warrants offered by Toulmin, Hitchcock, and myself, and lays out some of the reasons why I think a “Toulminesque” account of warrants captures crucial aspects of arguing more adequately than her account does.

We present a computational model of dialectical argumentation that could serve as a basis for legal reasoning. The legal domain is an instance of a domain in which knowledge is incomplete, uncertain, and inconsistent. Argumentation is well suited for reasoning in such weak theory domains. We model argument both as information structure, i.e., argument units connecting claims with supporting data, and as dialectical process, i.e., an alternating series of moves by opposing sides. Our model includes burden of proof as a (...) key element, indicating what level of support must be achieved by one side to win the argument. Burden of proof acts as move filter, turntaking mechanism, and termination criterion, eventually determining the winner of an argument. Our model has been implemented in a computer program. We demonstrate the model by considering program output for two examples previously discussed in the artificial intelligence and legal reasoning literature. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Philosophy and Rhetoric 34.2 (2001) 93-112 [Access article in PDF] Enthymemes, Common Knowledge, and Plausible Inference Douglas Walton The study of enthymemes has always been regarded as important in logic, critical thinking, and rhetoric, but too often it is the formal or mechanistic aspect of it that has been in the forefront. This investigation will show that there is a kind of plausibilistic script-based reasoning, of a kind that (...) has mainly been studied in artificial intelligence, that should have a much more important role to play in the study of enthymemes. But then curiously, as will also be shown, this plausibilistic type of reasoning was familiar in the ancient world, to the Sophists, as well as to leading philosophers such as Plato and Aristotle. By linking this ancient notion of plausibility to the modern notion used in computer science, this investigation reveals an important basis for the enthymeme that has a type of logical structure in its own right, but also has an informal aspect.An enthymeme, in current usage, is an argument that has one or more premises, or possibly a conclusion, not explicitly stated in the text, but that needs to have these propositions explicitly stated to extract the complete argument from the text. Sometimes enthymemes are described as arguments with "missing premises." That vocabulary is awkward, however, because the nonexplicit statement that needs to be added can be a conclusion, at least in a minority of cases. To make the exposition below smoother, the term nonexplicit assumption will be used to cover either the case of a nonexplicit premise or that of a nonexplicit conclusion. The problem with enthymemes is that if the nonexplicit assumptions in an argument are supposed to be propositions used by the arguer (as opposed to just the propositions needed to make the argument structurally correct, according to some standard), reasonable people can have differences of opinion on what the nonexplicit assumptions are supposed to be. The problem is that filling in the missing parts of enthymemes depends on interpreting the natural language [End Page 93] in which the argument was put forward to try to determine what the speaker meant to say.The solution to the problem comes through the recognition that enthymemes rest not only on formal (structural) criteria, but also on informal criteria. One of the most important of these informal criteria is something often called "common knowledge" (Govier 1992; Freeman 1995). But as shown below in a set of selected case studies of enthymemes, "common knowledge" is not really a kind of knowledge at all. It is really plausibility, or eikos, something well known in the ancient world and often misleadingly translated as "probability." Curiously, Aristotle's original doctrine of the enthymeme was based on this notion of plausibility. This historical fact has often been a source of puzzlement and confusion, and sometimes it has even been taken to indicate a defect or contradiction in Aristotle's treatment of the enthymeme. However, the goal of this investigation is not primarily historical. It is to work out one of the most important required steps toward a solution to the problem of enthymemes. But to do this, it is necessary to come back to the ancient notion of plausible inference. 1. The problem with enthymemes Once you have any formal theory of inference, like syllogistic, for example, you will be confronted by cases of arguments in everyday discourse that meet all the requirements for a structurally correct inference except that some part or parts, usually a premise or a conclusion, is missing. By "missing" is meant that the proposition in question has not been explicitly stated in the text of discourse, even though it may be clear enough that the speaker (writer) was relying on it, or including it, as part of the argument. The classic example is the following inference: All men are mortal; therefore, Socrates is mortal. To evaluate such an argument, surely some account of the "hidden" or "missing" assumption needs to be taken. The problem with enthymemes (Burke 1985; Gough and Tindale 1985; Hitchcock 1985) is that, if given carte... (shrink)

Christian Kock’s essays show the essential interconnectedness of practical reasoning, rhetoric and deliberative democracy. They constitute a unique contribution to argumentation theory that draws on – and criticizes – the work of philosophers, rhetoricians, political scientists and other argumentation theorists. It puts rhetoric in the service of modern democracies by drawing attention to the obligations of politicians to articulate arguments and objections that citizens can weigh against each other in their deliberations about possible courses of action.

My thesis situates itself within the field of the Philosophy of Worldviews. Specifically, it aims to address the normative question of what the task should be of such a philosophy when faced with the problem of conflicting beliefs between religious worldviews. To answer this question, I turn to the procedure of aporetical analysis, in short, aporetics. Firstly, aporetics offers a distinct method of consistency restoration within inconsistent sets on the basis of thesis rejection and thesis modification. Secondly, aporetics leads to (...) an understanding of the availability of aporetic exits on the basis of epistemic criteria. On the one hand, this leads us to opt for an orientational monism/pluralism, which steers the middle course between the epistemic stances of exclusivism and pluralism. On the other hand, it allows us to identify epistemic criteria for worldview acquisition on the basis of three distinct superclasses. These superclasses can be derived from Jürgen Habermas' validity claims, and applied to the self-understanding of contemporary theories of religion. (shrink)

The paper develops a classificatory system of basic argument types on the basis of the epis-temological approach to argumentation. This approach has provided strict rules for several kinds of argu-ments. These kinds may be brought into a system of basic irreducible types, which rely on different parts of epistemology: deductive logic, probability theory, utility theory. The system reduces a huge mass of differ-ent argument schemes to basic types and gives them an epistemological foundation.

Aristotle's conception and use of ta endoxa are key points to our understanding of Aristotelian dialectic. But, nowadays, they are not of historical or hermeneutic importance alone, as, in Aristotle's treatment of endoxa, we still see a relevant contribution to the modern study of argumentation. I propose here an interpretation of endoxa to that effect: namely, as plausible propositions. This version is not only defensible in the Aristotelian context, it may also shed new light on some of his assumptions and (...) methodological shortcomings – e.g. concerning the 'plausible/implausible' pair –; finally, it will even enable us to show certain basic hints and guidelines, advanced by Aristotle's study of endoxa, which still serve nowadays to orientate our studies of argumentation from the angle of a theory of plausible argument currently under construction. These hints and guidelines suggest a pragmatic, gradual and comparative discursive concept of plausibility, and point, in particular, towards the reasonable dealing with, and weighing up of, differences of opinion within this frame of reference. (shrink)

This paper makes a case for a refined look at the so- called ‘fallacy of hasty generalization’ by arguing that this expression is an umbrella term for two fallacies already distinguished by Aristotle. One is the fallacy of generalizing in an inappropriate way from a particular instance to a universal generalization containing a ‘for all x’ quantification. The other is the secundum quid (‘in a certain respect’) fallacy of moving to a conclusion that is supposed to be a universal generalization (...) containing a ‘for all x‘ quantification while overlooking qualifications that have to be added to the more limited kind of generalization expressed in the premise. It is shown that these two fallacies relate to two different kinds of generalization. (shrink)

This article asks whether an interdisciplinary "critical science studies" (CSS) is possible between a critical theory in the Frankfurt School tradition, with its commitment to universal standards of reason, and relativistic sociologies of scientific knowledge (e.g., David Bloor's strong programme). It is argued that CSS is possible if its practitioners adopt the epistemological equivalent of Rawls's method of avoidance. A discriminating, public policy–relevant critique of science can then proceed on the basis of an argumentation theory that employs an immanent standard (...) of relevance, which is illustrated by drawing on Helen Longino's critique of behavioral theory. (shrink)

Everyday life reasoning and argumentation is defeasible and uncertain. I present a probability logic framework to rationally reconstruct everyday life reasoning and argumentation. Coherence in the sense of de Finetti is used as the basic rationality norm. I discuss two basic classes of approaches to construct measures of argument strength. The first class imposes a probabilistic relation between the premises and the conclusion. The second class imposes a deductive relation. I argue for the second class, as the first class is (...) problematic if the arguments involve conditionals. I present a measure of argument strength that allows for dealing explicitly with uncertain conditionals in the premise set. (shrink)

The study of presumptions has intensified in argumentation theory over the last years. Although scholars put forward different accounts, they mostly agree that presumptions can be studied in deliberative and epistemic contexts, have distinct contextual functions, and promote different kinds of goals. Accordingly, there are “practical” and “cognitive” presumptions. In this paper, I show that the differences between practical and cognitive presumptions go far beyond contextual considerations. The central aim is to explore Nicholas Rescher’s contention that both types of presumptions (...) have a closely analogous pragmatic function, i.e., that practical and cognitive presumptions are made to avoid greater harm in circumstances of epistemic uncertainty. By comparing schemes of practical and cognitive reasoning, I show that Rescher’s contention requires qualifications. Moreover, not only do practical and cognitive presumptions have distinct pragmatic functions, but they also perform different dialogical functions and, in some circumstances, cannot be defeated by the same kinds of evidence. Hence, I conclude that the two classes of presumptions merit distinct treatment in argumentation theory. (shrink)

In this essay, Weinstein wants to address the issue of argument strength, of how strongly the premises of an argument support a conclusion. Using the framework of the Toulmin model, arguments have warrants which indicate some general connection between the premises and the conclusion of the argument. We may ask for the backing of the warrant, evidence for it. If the connection is an empirical generalization, the backing includes data supporting the generalization. But the backing may include theoretical generalizations, which (...) may explain the warrant. Furthermore, theories may be reduced by more comprehensive theories. A warrant then may ultimately be backed by some deep and very comprehensive theoretical explanation.Weinstein seeks to explicate the relation between the depth of backing for the warrant and the strength of the connection between premises and conclusion which the warrant indicates through the Model of Emerging Truth . Data relevant to confirming the theory have empir .. (shrink)

While the analytical philosophy of science regards inconsistent theories as disastrous, Chomsky allows for the temporary tolerance of inconsistency between the hypotheses and the data. However, in linguistics there seem to be several types of inconsistency. The present paper aims at the development of a novel metatheoretical framework which provides tools for the representation and evaluation of inconsistencies in linguistic theories. The metatheoretical model relies on a system of paraconsistent logic and distinguishes between strong and weak inconsistency. Strong inconsistency is (...) destructive in that it leads to logical chaos. In contrast, weak inconsistency may be constructive, because it is capable of accounting for the simultaneous presence of seemingly incompatible structures. However, paraconsistent logic cannot grasp the dynamism of the emergence and resolution of weak inconsistencies. Therefore, the metatheoretical approach is extended to plausible argumentation. The workability of this metatheoretical model is tested with the help of a detailed case study on an analysis of discontinuous constituents in Government-Binding Theory. (shrink)

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.

Current environmental problems and technological risks are a challenge for a new institutional arrangement of the value spheres of Science, Politics and Morality. Distinguished authors from different European countries and America provide a cross-disciplinary perspective on the problems of political decision making under the conditions of scientific uncertainty. cases from biotechnology and the environmental sciences are discussed. The papers collected for this volume address the following themes: (i) controversies about risks and political decision making; (ii) concepts of science for policy; (...) (iii) the use of social science in the policy making process; (iv) ethical problems with developments in science and technology; (v) public and state interests in the development and control of technology. (shrink)

We develop a conceptual and formal clarification of notion of surprise as a belief-based phenomenon by exploring a rich typology. Each kind of surprise is associated with a particular phase of cognitive processing and involves particular kinds of epistemic representations (representations and expectations under scrutiny, implicit beliefs, presuppositions). We define two main kinds of surprise: mismatch-based surprise and astonishment. In the central part of the paper we suggest how a formal model of surprise can be integrated with a formal model (...) of belief change. We investigate the role of surprise in triggering the process of belief reconsideration. There are a number of models of surprise developed in the psychology of emotion. We provide several comparisons of our approach with those models. (shrink)

In The Uses of Argument, Stephen Toulmin proposed a model for the layout of arguments: claim, data, warrant, qualifier, rebuttal, backing. Since then, Toulmin’s model has been appropriated, adapted and extended by researchers in speech communications, philosophy and artificial intelligence. This book assembles the best contemporary reflection in these fields, extending or challenging Toulmin’s ideas in ways that make fresh contributions to the theory of analysing and evaluating arguments.

Lilian Bermejo-Luque has posed these questions:1.What is the relationship between presumption and presumptive inference? 2.What are the correctness conditions for presumptions and presumptive inferences? Cohen’s method of relevant variables, Toulmin’s model, and Rescher’s theory of plausibility suggest answers. An inference is presumptive just in case its warrant transfers presumption from its premises to its conclusion. A warrant licencing an inference from the claim that an empirical property φ holds to the claim that some other property ψ holds is backed by (...) observation of a constant conjunction of those properties. The stronger the backing, the stronger the warrant. Warrants may be defeated by instances of φ holding in conjunction with some property χ and ψ not holding. The method of relevant variables directs us to organize such defeating properties into relevant variables. We then test the strength of a warrant by seeing how many variables fail to have a value which defeats the warrant. The more variables with no defeater, the stronger the warrant. We may construct a canonical ordering of the relevant variables by ranking them according to the plausibility of their including defeating values. We may evaluate the strength not only of empirically backed warrants, but warrants backed by institutional rules, such as a branch of law, or by a priori intuited connections between properties. An inference rule will be presumptive just in case the plausibility of its warrant being defeated is below some specified level. (shrink)

How can thought experiments lead to new empirical knowledge if they do not make use of empirical information? This puzzle has been widely discussed in the philosophy of science. It arises in conceptual metaphor research as well and is especially important for the clarification of its empirical foundations. The aim of the paper is to suggest a possible solution to the puzzle of thought experiments in conceptual metaphor research. The solution rests on the application of a novel metatheoretical framework that (...) conceives of linguistic theorizing as a process of plausible argumentation. The central idea of the solution is that through the dynamic feedback mechanism of the cyclic, prismatic and retrospective re-evaluation of information, thought experiments in conceptual metaphor research may indirectly supply the process of plausible argumentation with empirical knowledge. (shrink)

In [BAT 00b], the flat Rescher–Manor consequence relations — the Free, Strong, Argued, C-Based, andWeak consequence relation—were shown to be characterized by inconsistency-adaptive logics defined from the paraconsistent logic CLuN. This provided these consequence relations with a dynamic proof theory. In the present paper we show that the detour via an inconsistency-adaptive logic is not necessary. We present a direct dynamic proof theory, formulated in the language of Classical Logic, and prove its adequacy. The present paper contains the first direct (...) dynamic proof theory for consequence relations that are characterized by an adaptive logic. (shrink)

In all three of its manifestations, —abusive, circumstantial and tu quoque—the role of the ad hominem is to raise a doubt about the opposite party’s casemaking bona-fides.Provided that it is both presumptive and provisional, drawing such a conclusion is not a logical mistake, hence not a fallacy on the traditional conception of it. More remarkable is the role of the ad hominem retort in seeking the reassurance of one’s opponent when, on the face of it, reassurance is precisely what he (...) would seem to be ill-placed to give. Brief concluding remarks are given over to an examination of rival approaches to the ad hominem, especially those in which it is conceived of as a dialectical error. (shrink)

: For philosophers of science interested in elucidating the social character of science, an important question concerns the manner in which and degree to which the objectivity of scientific knowledge is socially constituted. We address this broad question by focusing specifically on philosophical theories of evidence. To get at the social character of evidence, we take an interdisciplinary approach informed by categories from argumentation studies. We then test these categories by exploring their applicability to a case study from high-energy physics. (...) Our central claim is that normative philosophy of science must move beyond abstract theories of justification, confirmation, or evidence conceived impersonally and incorporate a theoretical perspective that includes dialogical elements, either as adjuncts to impersonal theories of evidence or as intrinsic to the cogency of scientific argumentation. (shrink)

This article evaluates the strengths and weaknesses of arguments based on appeals to expertise. The intersection of two areas is explored: (i) the traditional argumentum ad verecundiam (literally, “appeal to modesty,” but characteristically the appeal to the authority of expert judgment) in informal logic, and (ii) the uses of expert systems in artificial intelligence. The article identifies a model of practical reasoning that underlies the logic of expert systems and the model of argument appropriate for the informal logic of the (...) argumentum ad verecundiam. (shrink)

John Pollock (1940?2009) was an influential American philosopher who made important contributions to various fields, including epistemology and cognitive science. In the last 25 years of his life, he also contributed to the computational study of defeasible reasoning and practical cognition in artificial intelligence. He developed one of the first formal systems for argumentation-based inference and he put many issues on the research agenda that are still relevant for the argumentation community today. This paper presents an appreciation of Pollock's work (...) on defeasible reasoning and its relevance for the computational study of argument. In our opinion, Pollock deserves to be remembered as one of the founding fathers of the field of computational argument, while, moreover, his work contains important lessons for current research in this field, reminding us of the richness of its object of study. (shrink)

Epistemologists have known for two-and-a-half centuries that there are serious difficulties surroundingnon-demonstrativeinference. The best-known problem,theproblem of induction, was first diagnosed by Hume in theTreatise. In our own century, several more problems were added, e.g., by Hempel —the paradox of the ravens—and by Goodman —the “new,” or exacerbated, problem of induction. But an even greater blow lay ahead: within the decade after Goodman's problem appeared, Gettier was to publish his famous challenge to the traditional analysis of knowledge which, again, underscored how (...) problematic inductive inferences are. (shrink)

Since its inception in the work on fallacies of Charles Hamblin, formal dialectic has been the object of an unparalleled level of optimism concerning the potential of its analytical contribution to fallacy inquiry. This optimism has taken the form of a rapid proliferation of formal dialectical studies of arguments in general and fallacious arguments in particular under the auspices of theorists such as Jim Mackenzie and John Woods and Douglas Walton, to name but a few. Notwithstanding the interest in, and (...) the hopes for, a formal dialectical analysis of the fallacies, such an analysis, I will demonstrate subsequently, leads to much unintelligibility in fallacy inquiry. The context of my argument will be the philosophical views of Hilary Putnam, particularly Putnam's claim that when we theorise in relation to rationality, the unintelligibility of the conception of rationality to emerge from this theoretical process can be traced to the circumscription of rationality within this theoretical process. I charge formal dialectic with effecting a similar circumscription of argumentative rationality, a circumscription that, I will claim, is generative of unintelligibility in formal dialectical analyses of the fallacies. In this case, the context for my claims will be the formal dialectical analyses of Walton and Batten, Rescher, Hamblin, Mackenzie and Hintikka, primarily in relation to the petitio principii fallacy. My conclusion examines a number of the reasons, both historical and conceptual, which have made it seem that it is possible to fully circumscribe the notion of argumentative rationality. (shrink)

Current practice in logic increasingly accords recognition to abductive, presumptive or plausible arguments, in addition to deductive and inductive arguments. But there is uncertainty about what these terms exactly mean, what the differences between them are (if any), and how they relate. By examining some analyses ofthese terms and some of the history of the subject (including the views of Peirce and Cameades), this paper sets out considerations leading to a set of definitions, discusses the relationship of these three forms (...) of argument to argumentation schemes and sets out a new argumentation scheme for abductive argument. (shrink)

First, ranking functions are argued to be superior to AGM belief revision theory in two crucial respects. Second, it is shown how ranking functions are uniquely reflected in iterated belief change. More precisely, conditions on threefold contractions are specified which suffice for representing contractions by a ranking function uniquely up to multiplication by a positive integer. Thus, an important advantage AGM theory seemed to have over ranking functions proves to be spurious.

The paper argues that the arguments from probability so popular in early Greek rhetoric and oratory essentially operate by appealing to common positions shared by both speaker and audience. Particularly in controversial debate provoked by fundamental dissensus they make their claim acceptable to the audience by pointing out a basic coherence or congruence of the speaker’s narrative with the audience’s own pre-established standards or standards of knowledge.

Defining qualified reasoning as reasoning containing such loose qualifying words as 'probably,' 'usually,' 'probable, 'likely,' 'ceteris paribus,' and 'primafacie, Ennis argues that typical cases of qualified reasoning, though they might be good arguments, are deductively invalid, implying that such arguments fail soundness standards. He considers and rejects several possible alternative ways of viewing such cases, ending with a proposal for applying qualified soundness standards, which requires employment of sufficient background knowledge, sensitivity, experience and understanding of the situation. All of this (...) takes place as part of the process, introduced elsewhere, of successively applying different legitimate sets of standards until one is found that is satisfied, or none is found, the latter calling for rejection of the argument, the former calling for its acceptance. (shrink)

"A Survey of Ranking Theory": The paper gives an up-to-date survey of ranking theory. It carefully explains the basics. It elaborates on the ranking theoretic explication of reasons and their balance. It explains the dynamics of belief statable in ranking terms and indicates how the ranks can thereby be measured. It suggests how the theory of Bayesian nets can be carried over to ranking theory. It indicates what it might mean to objectify ranks. It discusses the formal and the philosophical (...) aspects of the tight relation and the complementarity of ranks and probabilities. It closes with comparative remarks on predecessors and other philosophical proposals as well as formal models developed in AI. (shrink)

In this paper it is shown how plausible reasoning of the kind illustrated in the ancient Greek example of the weak and strong man can be analyzed and evaluated using a procedure in which the pro evidence is weighed against the con evidence using formal, computational argumentation tools. It is shown by means of this famous example how plausible reasoning is based on an audience’s recognition of situations of a type they are familiar with as normal and comprehensible in their (...) shared common knowledge. The paper extends previous work on this example by using three new multiagent argumentation schemes closely related to the scheme for argument from negative consequences. (shrink)

ABSTRACT We investigate a logic PFD, as introduced in [FA]. In our notation, this logic is enriched with operators P> r(r € [0,1]) where the intended meaning of P> r φ is “the probability of φ (at a given world) is strictly greater than r”. We also adopt the semantics of [FA]: a class of “F-restricted probabilistic kripkean models”. We give a completeness proof that essentially differs from that in [FA]: our “peremptory lemma” (a lemma in PFD rather than about (...) it) facilitates the construction of a canonical model for PFD considerably. We show that this construction can be carried out using only finitary means, and also give a filtration-technique for the intended models. We then define an alternative (in some sense more natural) semantics for the logic, and show some of its properties. Finally, we prove decidability of the logic. (shrink)

The paper relates two different fields of research: the historiography of generative linguistics and argumentation theory, a central topic of which is the investigation of fallacies. Relating the two fields is a challenge: Since fallacies seem to be at the heart of the historiography of generative linguistics, any thorough evaluation of its present state of the art also involves accounting for fallacies. The paper applies Kertész and Rákosi’s p-model of plausible argumentation to a case study on heated discussions in the (...) historiography of generative linguistics. As a result, basic properties of fallacious argumentation are revealed and delimited from plausible argumentation in linguistic historiography. In addition, the paper also draws generalizable conclusions that may affect the historiography of other human sciences as well. (shrink)

Este artículo presenta un análisis comparativo de los modelos de argumentación basados en las nociones de probabilidad subjetiva y de razonamiento plausible. Se hacen explícitos los “parecidos de familia” entre probabilidad y plausibilidad, y se examinan las diferencias en las prescripciones invocadas para la evaluación de tres tipos de falacias informales: apelación a la autoridad, a la popularidad y petición de principio. Se concluye que el razonamiento plausible, como Rescher y Walton lo describen, no proporciona una alternativa sólida a la (...) probabilidad como modelo normativo o descriptivo de la evaluación de argumentos. (shrink)