This book is based on lectures I gave at the Department of Mathematics and Statistics, University of Helsinki, during the academic year 2005–2006. I am indebted to the students who followed the course, in particular to Åsa Hirvonen, Meeri Kesälä, Ville Nurmi, Eero Raaste, and Ryan Siders. Thanks also go to Ville Nurmi for suggesting numerous corrections to the text, compiling the solutions to the exercises in the course, and for allowing me to include the solutions in this book. I am very grateful to Wilfrid Hodges for many useful discussions on dependence. I thank the Newton Institute (Cambridge, UK) for inviting me for the five weeks, during which time the final manuscript was prepared. The preparation of the manuscript was partially supported by grant 40734 of the Academy of Finland. I wish to thank Peter Thompson of Cambridge University Press for all the arrangements concerning publishing, and I am deeply grateful to Juliette Kennedy for her generous help in all stages of writing this book.

Invalid Structures

A key distinction recognized in Chapter 1 had to do with problems that arise within an argument with respect to the support that the premises provide for the conclusion, and also problems that arise “externally, ” between the argument and its context or audience. The last chapter illustrated both of these problems insofar as the Straw Man, for example, can involve an argument that is internally unproblematic but is fallacious because it is irrelevant to the original position in the context. Similarly, our discussion of ignoratio elenchi pointed to the failure of premises to provide any support for the conclusion.

This chapter pursues the last concern by looking at problems that arise with the structure or form of an argument. Here, the argument is presented as if the conclusion must follow, given the truth of the premises. But in fact, because of the way terms or propositions within the argument have been organized, the conclusion does not follow from the premises. Traditionally, the claim is that such an argument is invalid, and that invalidity is explained in relation to some particular fallacy. We can see then that one of the traditional features that Hamblin ascribes to Aristotle's definition – its invalidity – is particularly relevant here.

Straw Man

For some decades now, argumentation theorists have identified and analysed a fallacious type of argument called the Straw Man fallacy. Although Aristotle makes remarks that suggest a similar concern, the name of the fallacy and its treatment seem modern additions. It is not even mentioned by Hamblin in his seminal work on fallacies. The metaphor captured here reflects a strategy of rebellion or criticism that leads groups of people to build an effigy of a leader (usually with straw) and then attack or burn the effigy, thereby figuratively transferring their “attack” onto the real person. The thinking is that the real person is not available to the group in question and so the effigy serves as a kind of surrogate.

Transferred to the domain of argumentation, this strategy rarely involves any sense of rebellion, but it does retain the tone of a critique and dismissal of whoever or whatever is really at stake. The Straw Man fallacy involves the attribution or assumption of a position, which is then attacked or dismissed. The problem is that the position dismissed by the argument is not the real ‘man’ or ‘person’, but a caricature of the real position held. In a dialogue, a position may be explicitly attributed to an opponent. But for whatever reason, either that position is not one that the opponent actually holds, or the opponent does not hold the position in quite the way that has been attributed.

Principles of Analogy

One clear strategy of argumentation when reasoning about things that are uncertain is to see whether they are similar to things that we do know and then draw conclusions about them on the basis of the similarities. Logicians call this strategy the ‘Argument from Analogy’. An analogy is a comparison of two things or analogues. For example, Julian Huxley offered the following comparison: “The relation between predator and prey in evolution is somewhat like that between methods of attack and defence in the evolution of war.” In comparing these two things, Huxley hopes to shed light on the first pair because of what we know about the second pair. But Huxley is not here providing an Argument from Analogy, and the first thing we should note is not to assume that the presence of an analogy in argumentation means the argument scheme is being used. Huxley provides no details of how the two pairs are alike; nor, crucially, does he draw a conclusion on the basis of the similarities. This latter feature is a key identifying feature of the Argument from Analogy.

The basic fallacy associated with the Argument from Analogy is called False Analogy. Understanding how the scheme works does not explain how false analogies can arise and what it is that is wrong with them, but it does help us appreciate how analogical reasoning differs from the other types of reasoning we have discussed.

Correlations and Causal Reasoning

Near the end of Chapter 8, Case 8E involved the drawing of a generalization from a study that tried to establish a correlation between two things – having a busy social life and avoiding colds. Implicit in the conclusion is the causal claim that the first thing, the busy social life, caused or was a causal factor in the occurrence of the second thing, avoiding colds. The Argument from Correlation to Cause can be a reasonable argumentation scheme if it meets the correct conditions, but when these are not met, fallacious reasoning occurs.

In this chapter we will concentrate upon three types of causal reasoning that can prove problematic: (1) that which involves the concluding of a causal relation from a correlation or a mere temporal sequence, (2) reasoning that confuses the causal elements involved, and (3) that which predicts a negative causal outcome for a proposal or action, perhaps on the basis of an expected causal chain. The labels we will use for these three are post hoc reasoning, Misidentified Cause, and Slippery Slope reasoning.

Understanding causal reasoning and determining when it is fallacious are made difficult by the lack of any clear agreement on how to analyze the concept of causation. We will be able to detect cases in which something is clearly wrong with a causal argument, but more contentious cases will be a different matter.

Introduction

As we saw in Chapter 1, Aristotle divided fallacies into those that depended on language and those that did not. Since then among fallacy theorists this has been a popular approach to the organization of fallacies. Until recently, many theorists even repeated the fallacies of language that Aristotle had identified, even where these made little contemporary sense. More recently, we have seen the list expanded to include “new” fallacies of language that reflect modern usage and experience.

On the question of which problems of language are fallacies we also encounter some of the deeper issues of what is to count as a fallacy. Some traditional fallacies of language are not arguments, for example, and some that are do not seem to be invalid. Both these points will be discussed in relation to fallacies taken up in this chapter.

Aristotle's list of fallacies that depend on language numbered six: Equivocation, Amphiboly, Combination of Words, Division of Words, Accent, and Form of Expression. The first two of these can still be found in contemporary lists in the way that Aristotle understood them. We will return to these later. The other four, where they have been retained, have undergone considerable revision of meaning. Aristotle's combination of words and division of words differ considerably from their contemporary instantiations as the fallacies of composition and division. Aristotle was concerned with the ways in which combining and dividing words alter meanings.

Strong and Weak Arguments

Arguments have a range of types and employ a diversity of devices, from those that press a historical case using causal reasoning to those that recommend an economic course of action by appealing to an authority in the field. They will be characterized by a particular structure, where one or more statements (premises) are given in support of a conclusion, and a range of intentions: to persuade an audience, to resolve a dispute, to achieve agreement in a negotiation, to recommend an action, or to complete an inquiry. Because of these different intentions, arguments arise in different contexts that are part of the argumentative situation. Arguments also have a range of strengths, from those that conform to the principles of good reasoning to those that commit some of the more abysmal errors we will be considering in this book. In between are degrees of strength and weakness. In fact, many arguments of a more extended nature will admit of merits and demerits that can make our judgment about the overall quality of the reasoning quite difficult. A ‘fallacy’ is a particular kind of egregious error, one that seriously undermines the power of reason in an argument by diverting it or screening it in some way. But a more precise definition is difficult to give and depends on a range of considerations.

Introduction

As some of our earlier discussions have indicated, one major variety of reasoning in which we engage is inductive reasoning, whereby a conclusion is drawn on the basis of experience that is in some way incomplete. We decide that something will be a certain way because we, and perhaps others, have found it to be that way in the past. What we are drawing from for our evidence is what we take to be a representative sample of cases of the thing in question. The better the sample, or range and depth of experience, the more justified is the conclusion drawn from it. The most public way in which we see this kind of reasoning is through the reported results of opinion polls.

As early as the Port Royal Logic (1662) logicians have identified invalid inductions as a species of fallacy. Inductions based on fewer than all instances, we are told, often lead us into error. But we inevitably have to reason on the basis of fewer than all instances, so the opportunities for error are extensive. The question is how few instances we can accept before the conclusion we draw is unjustified, and the answer will depend on the contexts involved and the types of things we are reasoning about. The fallacy that arises when we conclude too much on too little evidence has come to be called the Hasty Generalization.

Introduction

In the wide public domain, where controversial issues are debated and personalities invariably clash, the strategy of attacking an opponent because of some real or perceived characteristic, circumstance, or association is particularly prevalent. The strategy of attacking the person falls under the general umbrella of ethotic arguments, that is, arguments that deal with some feature of the character of the speaker. Where the attack is problematic in particular ways, we charge the attacker with committing the fallacy called argumentum ad hominem (argument against the person). We have to be clear that we are speaking here of the fallacy involved in this strategy. While the textbook tradition for a long time treated all such arguments as fallacious, more recent treatments have appreciated that it is often quite appropriate to draw attention to some feature of a person's character or circumstances when it has a direct bearing on what that person says. Part of the previous confusion was due to the extreme looseness of many textbook treatments of this fallacy. There is also the further complication that the way the ad hominem has been understood and treated over time has changed. We need to consider some of this history and then fix on what modern treatments identify as problematic.

The first philosopher to draw attention to the ad hominem is John Locke (1632–1704), although he does not claim to have invented the term, and Hamblin attributes the idea, if not the title, to Aristotle.

Introduction

The last two chapters have concentrated on ‘ad’ arguments, appeals to components of our experience that offer to support a variety of claims. One further ‘ad’ argument that deserves fuller study is ad verecundiam, or the Appeal to Authority or Expertise.

The Appeal to Authority is a strategy in argument that few can avoid making. When my doctor tells me that I must make some serious lifestyle changes or else expect undesirable consequences to follow, then my deliberations in deciding whether to make such adjustments involve a direct appeal to her status as an authority. She has knowledge that I do not possess, coupled with many years of experience reviewing the symptoms of people comparable to me. In principle, I could acquire this knowledge and experience directly, but it is simply not practical for me to enter medical school and subsequent practice as a family physician. In the absence of the direct evidence that it is not practical for me to acquire, I rely on the testimony of an expert. Similar situations govern a wide range of my interactions with people or sources that are judged authorities of some description. In the extremely complex world in which we live, no one can be expected to be knowledgeable about everything that affects him and so we must necessarily rely on and trust the say-so of other people. The issue is deciding when that trust is well placed and when it is not.

This latest addition to the Cambridge series in Critical Reasoning and Argumentation is a study of bad reasoning, principally as conveyed through traditional and modern fallacies. While the study of fallacies has a long and detailed history, the bulk of critical literature on the fallacies has appeared in the last three or four decades. So much that is new and interesting can be drawn into a full study of the fallacies. The rationale behind this volume is to introduce students to the study of fallacy by means of the latest research in the field, along with some of the standard ideas that have remained relevant since the time of Aristotle. Thus, each topic and fallacy is couched within a discussion of current thinking, providing the clearest explanation possible of both what goes wrong in some of the more prevalent patterns of fallacious reasoning and why arguers and audiences might be misled by such errors.

One thing the recent literature has made very clear is that fallacies are far more complex, and thus deserving of much fuller analyses, than the traditional textbook treatments have suggested. Too often, fallacies are assigned a label and a brief description, along with an admonition to students to avoid such mistakes in their own reasoning.

Introduction

Over time, the arguments ‘ad’, as we might call them, have become quite a sizable group. As a genre they arose with Locke, but logicians have felt free to add to them, particularly throughout the last two centuries. Hence, Hamblin provides a list that includes the argumenta ad fidem (Faith), superbiam (Pride), odium (Hatred), amicitiam (Friendship), invidiam (Envy), and many more. In this chapter, we will explore four of the more frequently occurring ‘ad’ fallacies, the argumenta ad populum (Popularity), baculum (Force), misericordiam (Pity), and Ignorantiam (Ignorance). Then, in the next chapter, we will consider the argumentum ad verecundiam, now treated as the Appeal to Authority, in more detail.

What the ‘ad’ fallacies have in common, besides names derived from Latin terms, is that they are appeals to some contextual factors that characterize the type of argument involved. These factors give some clues to where we might expect to meet them. The ad baculum, for example, often arises in confrontations or arguments in which some kind of power or authority is asserted. The ad misericordiam occurs in contexts in which some special consideration is being sought on emotional grounds. And the ad ignorantiam is frequently found in inquiries in which knowledge claims are being advanced. As does the ad hominem of the previous chapter, these fallacies arise in the processes of argumentation itself.

The scholastic identification of desiring and conceiving to be good, of motivational and evaluative attitudes, faces a challenge from cases of akrasia. In cases of akrasia, agents are not motivated in accordance with comparative evaluations. An akratic agent will think that A is better than B yet pursue B. In these cases, the agent's motivational states seem not to fall in line with his evaluative states.

It is not completely uncontroversial that accidie and akrasia are indeed possible, at least if described as cases in which the agent's motivation does not correspond with his evaluative judgments. However, denying this possibility seems like denying the phenomena; we at least seem to confront instances of these kinds of behavior often enough. The existence of phenomena that correspond to these descriptions of akrasia seems to be a major argument against the scholastic view in the context of intentional explanations and in favor of separatist views, views that allow motivation and evaluation to come completely apart. The aim of this chapter is to show not only that the scholastic view has the right tools to account for akrasia but also that it accounts for the phenomena better than separatist views.

THE PROBLEM WITH AKRASIA

In the Protagoras, Socrates says that most people