Informal Logic

The standard definition of “argument” is satisfied by any series of statements in which one (of the statements) is marked as the conclusion of the others. This leads to the counter-intuitive result that “I like cookies, therefore, all swans are white” is an argument, since “therefore” marks “all swans are white” as the conclusion of “I like cookies”. This objection is often disregarded by stating that, although the previous sequence is an argument, it fails to be a good one. However, (...) when we compare our previous argument with a definitely bad argument like “this swan is white, therefore, all swans are white”, we see that there is an important difference between them. Whereas the former fails to fulfil our intuition of what an argument is, the latter does qualify as an argument, but as a bad one. In this talk, I will sketch a definition that better captures this feature of our intuition of what an argument is in three steps. Following Díez and Moulines (1999), I first reduce inductive validity to deductive validity through what we may call the method of deductivisation. Second, through epistemic predicates (cf. Thompson 2002), I introduce a broader concept of validity that accounts not only for deductive and inductive validity, but also for a weaker type of validity that may be called pseudo-validity. I show that these pseudo-valid arguments can also be deductivised with the help of the above-mentioned epistemic predicates. Finally, I re-define the concept of argument as any series of statements that is at least pseudo-valid, which leaves the “cookies argument” outside of this definition. (shrink)

Two common claims in philosophy are that deep disagreements cannot, in principle, be resolved by argument and that normal disagreements will be resolved by argument. In each claim it is assumed that the parties to the disagreement are rational. I argue that both claims are false. The first fails to take account of refutations. The second fails to recognise the role of conjectures in the dynamics of the growth of knowledge. There is no disagreement such that it is impossible for (...) rational parties to reach agreement by argument; but there is also no disagreement for which parties are rationally required to reach agreement by argument. Given the same evidence, it may be rational for one person to believe a specific proposition and another to believe its negation. (shrink)

I distinguish arguments and arguing and I explain some important logical features of arguments. I then explain how philosophers have been misled, apparently by Euclid, into giving seriously mistaken accounts of arguing. I give a few examples. I then offer a seven-step guide on how to argue. After that, I conclude.

It is usually accepted that unconditional statements are clearer and less problematic than conditional ones. This article goes against this popular belief by advancing the contrarian hypothesis that all unconditional statements can be reduced to conditional ones due to the way our assumptions support our assertions. In fact, considering the coherentist process by which most of our different beliefs mutually support themselves, the only genuine example of unconditional statements are cases of self-justified beliefs, but these examples are controversial and few (...) and far between. The distinction between unconditional and conditional statements is similar to the distinction between assumptions and premises in that is a largely conventional idealisation that results from our attempts to limit epistemic complexity. (shrink)

It is usually accepted that deductions are non-informative and monotonic, inductions are informative and nonmonotonic, abductions create hypotheses but are epistemically irrelevant, and both deductions and inductions can’t provide new insights. In this article, I attempt to provide a more cohesive view of the subject with the following hypotheses: (1) the paradigmatic examples of deductions, such as modus ponens and hypothetical syllogism, are not inferential forms, but coherence requirements for inferences; (2) since any reasoner aims to be coherent, any inference (...) must be deductive; (3) a coherent inference is an intuitive process where the premises should be taken as sufficient evidence for the conclusion, which on its turn should be viewed as a necessary evidence for the premises in some modal range; (4) inductions, properly understood, are abductions, but there are no abductions beyond the fact that in any inference the conclusion should be regarded as a necessary evidence for the premises; (5) motonocity is not only compatible with the retraction of past inferences given new information, but it is a requirement for it; (6) this explanation of inferences holds true for discovery processes, predictions and trivial inferences. (shrink)

Studies in Communication Sciences, 6, 2006, 3-26 . [link to online version posted].

In this paper, we introduce the methodology and techniques of meta-argumentation to model argumentation. The methodology of meta-argumentation instantiates Dung’s abstract argumentation theory with an extended argumentation theory, and is thus based on a combination of the methodology of instantiating abstract arguments, and the methodology of extending Dung’s basic argumentation frameworks with other relations among abstract arguments. The technique of meta-argumentation applies Dung’s theory of abstract argumentation to itself, by instantiating Dung’s abstract arguments with meta-arguments using a technique called flattening. (...) We characterize the domain of instantiation using a representation technique based on soundness and completeness. Finally, we distinguish among various instantiations using the technique of specification languages. (shrink)

Feminists note an association of arguing with aggression and masculinity and question the necessity of this connection. Arguing also seems to some to identify a central method of philosophical reasoning, and gendered assumptions and standards would pose problems for the discipline. Can feminine modes of reasoning provide an alternative or supplement? Can overarching epistemological standards account for the benefits of different approaches to arguing? These are some of the prospects for argumentation inside and outside of philosophy that feminists consider. -/- (...) The further concern is that the academic study of argumentation – in philosophy and other disciplines – has failed to account for the type of reasoning needed for social justice movements. What resources for addressing these concerns can be found in informal logic and interdisciplinary argumentation theory? Since part of the perceived problem derives from assuming that arguing is a contest, are more collaborative epistemological frameworks better? Can regular politeness or civility hedge against undesirable tendencies of argumentation? Can “critical thinking” pedagogy involving argument educations answer the needs of social justice? (shrink)

BAT is a logic built to capture the inferential behavior of informal provability. Ultimately, the logic is meant to be used in an arithmetical setting. To reach this stage it has to be extended to a first-order version. In this paper we provide such an extension. We do so by constructing non-deterministic three-valued models that interpret quantifiers as some sorts of infinite disjunctions and conjunctions. We also elaborate on the semantical properties of the first-order system and consider a couple of (...) its strengthenings. It turns out that obtaining a sensible strengthening is not straightforward. We prove that most strategies commonly used for strengthening non-deterministic logics fail in our case. Nevertheless, we identify one method of extending the system which does not. (shrink)

This article seeks, first, to show that much of the existing normative work on argument from expert opinion (AEO) is problematic for failing to be properly informed by empirical findings on expert performance. Second, it seeks to show how, with the analytic tool of Bayesian reasoning, the problem diagnosed can be remedied to circumvent some of the problems facing the scheme-based treatment of AEOs. To establish the first contention, we will illustrate how empirical studies on factors conditioning expert reliability can (...) be drawn upon to re-construct. Walton’s critical questions matching the scheme of AEOs. To establish the second contention, we will illustrate how Walton’s re-constructed set of critical questions can be formalized within a Bayesian network. Finally, we will highlight how the specific ways in which the Bayesian framework we propose is both continuous with and distinct from the models of source reliability put forward by theorists like Bovens and Hartmann (2003). (shrink)