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.

Donepezil, an acetylcholinesterase inhibitor used in the treatment of Alzheimer's disease, has been widely cited in media and bioethics literature on cognitive enhancement (CE) as having the potential to improve the cognitive ability of healthy individuals. In both literatures, this claim has been repeatedly supported by the results of a small study published by Yesavage et al. in 2002 on non-demented pilots (30-70 years old). The factors contributing to this specific interpretation of this study's results are unclear.

In this paper, I argue that arguments from expert opinion, i.e., inferences from “Expert E says that p” to “p,” where the truth value of p is unknown, are weak arguments. A weak argument is an argument in which the premises, even if true, provide weak support—or no support at all—for the conclusion. Such arguments from expert opinion are weak arguments unless the fact that an expert says that p makes p significantly more likely to be true. However, research on (...) expertise shows that expert opinions are only slightly more accurate than chance and much less accurate than decision procedures. If this is correct, then it follows that arguments from expert opinion are weak arguments. (shrink)

Gilles Deleuze takes up the challenge to create a philosophy of the interesting, the remarkable and the unusual. He does this in what Alain Badiou calls the ‘‘Grand Style’’, the style of Descartes, Spinoza and Kant whose philosophies arise in relation to developments in the natural sciences and mathematics. Grounding himself in the molar-molecular pair, Deleuze sets out a new image of thought. He conceptualises an immanent but still relatively closed, deterministic, atomistic and reversible system that is not immediately reduced (...) to entropic equilibrium because its processes take place on the molecular level, at speeds which he hypothesises are beyond the speed of light. He postulates a manifold, a sphere of immanence that is the entire universe and not merely the Earth or our solar system. It is a system governed by sensitivity to initial starting points and unstable boundaries, thus although it is chaotic as well as probabilistic, it remains a mathematically formal, deterministic system. (shrink)

In this paper, I argue that ad hominem arguments are not always fallacious. More explicitly, in certain cases of practical reasoning, the circumstances of a person are relevant to whether or not the conclusion should be accepted. This occurs, I suggest, when a person gives advice to others or prescribes certain courses of action but fails to follow her own advice or act in accordance with her own prescriptions. This is not an instance of a fallacious tu quoque provided that (...) such circumstantial ad hominem arguments are construed as rebuttals to appeals (administrative) authority (of expertise), or so I argue. (shrink)

I shall show that the main argument forms of Wittgenstein's Tractatus and Kant's Critique of Pure Reason are Modus Tollens. I shall then argue that the main arguments of both books beg the question by addressing only one sub-argument in each, although it is still in controversy whether begging the question is a genuine fallacy.

Woods and Walton deserve credit for including a discussion of “economic reasoning” and its susceptibility to the “fallacy of composition.” Unfortunately, they did not sufficiently pursue the topic, and argumentation scholars have apparently ignored their pioneering effort. Yet, obviously, economic argumentation is extremely important, and economists constantly harp on this fallacy. This paper calls attention to this problem, elaborating my own approach, which is empirical, historical, and meta-argumentational.

Recently, individualized or personalized medicine (PM) has become a buzz word in the academic as well as public debate surrounding health care. However, PM lacks a clear definition and is open to interpretation. This conceptual vagueness complicates public discourse on chances, risks and limits of PM. Furthermore, stakeholders might use it to further their respective interests and preferences. For these reasons it is important to have a shared understanding of PM. In this paper, we present a sufficiently precise as well (...) as adequate definition of PM with the potential of wide acceptance. (shrink)

In view of the confusion about the use of the term ‘population’ in biology, an analysis has been made of the use of the concept of population in biology. Origin and development, logic and epistemology of the population-concept have been investigated for that purpose. It appears that several concepts of population coexist in biology. The term ‘population’ is used for all these concepts, so it is not amazing that confusion has arisen. This confusion is the more dangerous, since ‘population’ plays (...) an important part in the theory of evolution. A modus has been suggested to diminish this confusion by defining ‘population’ in a very wide sense of the term and by proposing a ‘deme’—terminology to specify the various special concepts of population. (shrink)

On the nature of definitions and concepts, and the definition of critical thinking.

In her recent Counter-Reply to my views, Evelyn Pluhar defends her use of literature on nutrition and restates her argument for moral vegetarianism. In his Vegan Ideal article, Gary Varner claims that the nutrition literature does not show sufficient differences among women, men, and children to warrant concern about discrimination. In this response I show how Professor Pluhar continues to draw fallacious inferences: she begs the question on equality, avoids the main issue in my ethical arguments, argues from irrelevancies, misquotes (...) her sources, equivocates on context, confuses safety with morality, appeals to fear, confuses correlation with cause, fails to evaluate scientific studies, draws hasty conclusions from insufficient data, ignores a large amount of data which would call her views into question, does not follow good scientific or moral argumentation, objectionably exceeds the limits of her expertise, and resorts to scapegoating. I also argue that Professor Varner fails to make his case because he offers virtually no evidence from scientific studies on nutrition, relies on outdated and fallacious sources, makes unsupported claims, ignores evidence that would contravene his claims, draws hasty conclusions based on weakly supported hypotheses rather than facts, employs a double standard, appeals to ignorance, does not evaluate arguments from his sources, and makes anad hominem attack on a respected nutritionist when his focus should be on evaluating the evidence and arguments from the scientific studies themselves. Neither Varner nor Pluhar have responded sufficiently to the real issue in my arguments, that of discrimination and bias in the vegan ideal. (shrink)

I here discuss an argument frequently dismissed as a fallacy – the slippery slope or camel's nose. The argument has three forms – analogical, argumentative, and prudential. None of these provides a deductive guarantee, but all can provide considerations capable of influencing the intellect. Our evaluation of such arguments reflects our background social and evaluative assumptions.

A popular three-stage argument appraisal strategy calls for (1) identifying the parts of the argument, (2) classifYing the argument as deductive, inductive, or some other type, and (3) appraising the argument using the standards appropriate for the type. This strategy fails for a number of reasons. I propose a comprehensive alternative approach that distinguishes between inductive, deductive, and other standards; calls for the successive application of standards combined with assumption-ascription, according to policies that depend for their selection on the goals (...) of the appraiser; and provides for qualified reasoning. (shrink)

Dictionaries distinguish the following senses of ‘punishment’:the act of punishing, or the fact of being punished - where ‘punish’ is defined as: an act of public authority causing an offender to suffer for an offense. As In: ‘the respectable not only obey the law, but punish those who refuse to do so’.that which is inflicted as a penalty for an offense. As in: ‘all punishments are to be carried out in the Barrack Yard’, ‘fit the punishment to the crime’.severe handling (...) or treatment causing heavy damage, injury or loss. As in: ‘the fighter had been subjected to heavy punishment in his losing bout’, ‘the ships received considerable punishment from the batteries’. (shrink)

In a priori analogies, the analogue is constructed in imagination, sharing certain properties with the primary subject. The analogue has some further property clearly consequent on those shared properties. Ceteris paribus the primary subject has that property also. The warrant involves non-empirical, e.g., moral intuition but is also defeasible. The argument is thus neither deductive nor inductive, but an additional type. In an inductive analogy, the analogues back the warrant from below. Distinguishing these two types of arguments by analogy gives (...) epistemic evaluative factors primacy over resemblance factors in classifying arguments—a prescient insight on Govier’s part. (shrink)