Probabilistic argumentation systems: A new way to combine logic with probability

Probability is usually closely related to Boolean structures, i.e., Boolean algebras or propositional logic. Here we show, how probability can be combined with non-Boolean structures, and in particular non-Boolean logics. The basic idea is to describe uncertainty by (Boolean) assumptions, which may or may not be valid. The uncertain information depends then on these uncertain assumptions, scenarios or interpretations. We propose to describe information in information systems, as introduced by Scott into domain theory. This captures a wide range of systems of practical importance such as many propositional logics, first order logic, systems of linear equations, inequalities, etc. It covers thus both symbolic as well as numerical systems. Assumption-based reasoning allows then to deduce supporting arguments for hypotheses. A probability structure imposed on the assumptions permits to quantify the reliability of these supporting arguments and thus to introduce degrees of support for hypotheses. Information systems and related information algebras are formally introduced and studied in this paper as the basic structures for assumption-based reasoning. The probability structure is then formally represented by random variables with values in information algebras. Since these are in general non-Boolean structures some care must be exercised in order to introduce these random variables. It is shown that this theory leads to an extension of Dempster–Shafer theory of evidence and that information algebras provide in fact a natural frame for this theory.     

Modelling argumentation and modelling with argumentation

This paper discusses the epistemological and methodological bases of a scientific theory of meaning and proposes a detailed version of a formal theory of argumentation based on Anscombre and Ducrot's conception. Argumentation is shown to be a concept which is not exclusively pragmatic, as it is usually believed, but has an important semantic body. The bridge between the semantic and pragmatic aspects of argumentation consists in a set of gradual inference rules, called topoi, on which the argumentative movement is based. The content of each topos is determined at the pragmatic level, while the constraints on the forms of the topoi attached to a sentence are determined at the semantic level. Applications and possible applications toartificial intelligence and to cognitive sciences are discussed. In particular, the gradual models used to account for argumentation are shown to be extremely promising for Knowledge management, a discipline which includes knowledge acquisition, knowledge representation, transmission of knowledge (communication, interfaces, etc.), knowledge production (decision help, reasoning, etc.). A first formal model is presented and discussed: it is shown in details how it accounts for most of the argumentative features of sentences containing but, little and a little, and how it can be extended to describe sentences containing other argumentative connectives. However, this model is shown to be too simple and to violate the compositionality principle, which is shown, in the first section, to bean important methodological principle for any scientific theory. After a detailed analysis of the possible reasons for this violation, an improved model is proposed and its adequacy is discussed.     

Coalescent argumentation

Coalescent argumentation is a normative ideal that involves the joining together of two disparate claims through recognition and exploration of opposing positions. By uncovering the crucial connection between a claim and the attitudes, beliefs, feelings, values and needs to which it is connected dispute partners are able to identify points of agreement and disagreement. These points can then be utilized to effect coalescence, a joining or merging of divergent positions, by forming the basis for a mutual investigation of non-conflictual options that might otherwise have remained unconsidered. The essay proceeds by defining and discussing argument, position and understanding. These notions are then brought together to outline the concept of coalescent reasoning.     

Practical-theoritical argumentation

This essay explores the dialectics of theory and practice in terms of argumentation theory. Adapting Jonsen and Toulmin's (1988) notion of a Theory-Practice spectrum, it conceives Theory and Practice as extreme ends of a continuum and discourses as falling at various points along the continuum. Every theoritical discourse has essential practical aspects, and every practical discourse has essential theoretical aspects. Practices are theorized to varying degrees but every practice is thorized to some degree. Reflective discourse, which is discourse about practice, moves to and fro along the Theory-Practice continuum. Reflective discourse involves argumentation. Practical argumentation connects theory to practice; it appeals to general warrants, which may be simple or may tap into elaborate conceptual structures, in order to establish grounds for practical judgments. A practical discipline is a relatively coherent intellectual-professional enterprise that cultivates a field of social practice by engaging within itself and with practitioners in a reflective discourse. The argumentation of a practical discipline, like ordinary practical reflection, moves to and fro along the Theory-Practice continuum but in more methodical steps informed by systematic methodological reflection on the reflective process itself.     

Suppositions in argumentation

The atheist who begins to argue his case by saying, Suppose there is an omniscient Being of the sort in which Christians believe ... is employing a very familiar move in argumentation. However, most books on argumentation theory ignore suppositions completely. Searle omits suppositions entirely from his taxonomy of speech acts and this appears to lead to a similar omission in Speech Acts in Argumentative Discussions by van Eemeren and Grootendorst.This paper argues that suppositional argument is elegant, powerful and extremely common, that the correct way to understand it is based on Gottlob Frege's distinction between asserted and unasserted propositions and hence that suppositions are neither assertions nor (and this is more important) assertives. The paper discusses the connections between suppositions and conditionals; it argues that argumentation theory which ignores suppositions is systematically misleading; and it concludes by indicating some possible developments in argumentation theory.Revised version of a paper delivered at the University of Amsterdam, April 3, 1987.     

Manipulations in argumentation

In public and political practice, argumentation involves verbal manipulations, which have not been sufficiently studied in modern argumentation theory. This paper proposes to analyse such manipulations as speech acts, by means of the pragmadialectical theory of argumentation.     

Culture and collective argumentation

What are the mechanisms underlying the reproduction and change of collective beliefs? The paper suggests that a productive and promising approach for dealing with this question can be found in ontogenetic and cross-cultural studies on ‘collective argumentations and belief systems’; this is illustrated with regard to moral beliefs: After a short discussion of the rationality/relativity issue in cultural anthropology some basic elements of a conceptual framework for the empirical study of collective argumentations are outlined. A few empirical case studies are summarized; the results deliver some empirical evidence to the assumption that as the ‘logic of collective argumentations’ develops in children and adolescent there will be different and increasingly more complex constraints on the kinds of basic moral beliefs that can be collectively accepted. Most importantly, as children approach adolescence they may have acquired a ‘logic of argumentation’ which makes possible a collectively valid distinction between the ‘is’ and the ‘ought’ of some disputed particular moral issue. A comparison with a land litigation among Trobriands (Papua New Guinea) shows that the ‘logic of argumentation’ and the corresponding basic moral beliefs of Trobriands very much resemble the ‘logic of argumentation’ and moral rationality standards of (German) adolescents.     

Indirect directives in monological argumentation

The paper deals with sentence adverbials and clauses with the propositional content no doubt can be cast on ... and their occurrence in monological argumentative discourse. Such adverbials and clauses are regarded as illocutionary indicators of indirect directives aiming at the verbal behaviour of the reader, or, more precisely, at the omission of verbal activity on reader's part. Such attempts to influence the reader's behaviour can be both fair ones, to anticipate reader's objections, but also manipulative ones, so as to suppress them. That is why some general guidelines are given how to distinguish between the discourse-organizing and the manipulative function of indirect directives in concern.     

Reasoning serves argumentation in children

The argumentative theory of reasoning (Mercier & Sperber, in press-c) claims that reasoning evolved for argumentation: to find and evaluate arguments in dialogic contexts. The theory has drawn most of its supportive evidence from work with adults, leaving open the possibility that argumentive features of reasoning are in fact entirely learned. Evidence is reviewed here suggesting that the special relation between reasoning and argumentation holds at all ages. More specifically, it is argued that (a) children possess at least rudimentary argument skills, (b) they are able to reap the benefits of social reasoning from very early on, (c) confirmation bias is present as soon as they start to argue, and (d) children can be victims of the same biases that affect adults when they use reasoning in the wrong contexts. These claims strengthen the argumentative theory of reasoning and support a call for more research on the interactive features of reasoning in both adults and children.     

Rules for argumentation in dialogues

In this article it is pointed out what kind of rules for communication and argumentation are required in order to make it possible to resolve disputes in an orderly way. In section 2, Gricean maxims and Searlean speech act conditions are integrated in such a way that five general rules for communication can be formulated. In section 3, starting from Lewis's definition of convention, it is argued that the interactional effect of accepting is conventionally linked with the complex communicative act complex of argumentation. In section 4, the rules for argumentation are placed in a dialogical perspective.     

Patterns of argumentation in Galileo's Discorsi

In this contribution I intend to reconstruct and evaluate one of Galileo's famous arguments given in the Discorsi against a well‐entrenched thesis of Aristotelian physics. It will be shown that Galileo's reduction‐to‐the‐absurd type of counterargument is, although seemingly cogent, after all fallacious. I ascribe Galileo's committing of this fallacy to his looking at the Aristotelian physics through the (Kuhnian type) paradigmatic “spectacles” of his own new physics.     

Ad hominem arguments in practical argumentation

This paper is ultimately about the nature of argumentation in general and about the nature of practical argumentation in particular. (Practical argumentation is the form of argumentation which aims at answering the question: ‘What is to be done?’) The approach adopted here is an indirect one. I analyze one traditional form of argumentive fallacyargumentum ad hominem and try to show that in some argumentative situations it is an intuitively legitimate move. These intuitions can be explained if we accept that practical argumentation is also governed by the general rules of practical rationality.     

The rhetorical foundation of philosophical argumentation

The rejection of rhetoric has been a constant theme in Western thought since Plato. The presupposition of such a debasement lies at the foundation of a certain view of Reason that I have called propositionalism, and which is analyzed in this article. The basic tenets of propositionalism are that truth is exclusive, i.e. it does not allow for any alternative, and that there is always only one proposition which must be true, the opposite one being false. Necessity and uniqueness are the ideals of propositionalism. But the question of the necessity of such a necessity is bound to arise. Foundationalism and propositionalism are intrinsically related. Since necessity excludes alternatives, rhetoric, which is based on the possibility of opposite standpoints, is unavoidably devalued as the crippled child of Reason, identical to sophistry or eristic. But propositionalism cannot justify itself and provide a justification for its own foundation without circle or contraditction. Since it responds to the problem of eradicating problems and alternatives through propositional entities, propositionalism is ultimately based on questioning to which it replies in the mode of denial. The unavowed foundation of Reason is therefore the question of questioning, even though this very question is suppressed as propositionalism. The trace of such a question is not only historical, but can also be seen, for instance, in the role played by the principle of contradiction in the constitution of propositional Reason (Artitotle): opposite propositions are not the expression of a problematic situation, they are either possible or successively unique propositions.We want to replace propositionalism by problematology which allows for the conceptualization of alternatives, thereby rendering a true rhetoric possible. Argumentation cannot then be equated with eristic any more, as propositionalism maintained.Rationality must be seen as having questioning as its true starting-point. Reason must be rhetorical if it is to survive the death of propositionalism which took place after the radical criticisms of Marx, Nietzsche and Freud. Even if it is still hard ffor philosophers and rhetoricians to think within another framework and even though they prefer endlessly to deconstauct the old one instead of changing it, problematology is bound to impose itself as the new voice for rationality, because Reason has always endeavored to solve problems. Propositionalism has been only one way of conceiving problems, based on the view that solutions could be but the suppression of questioning.