A Rulebook for Arguments (5th Edition) PDF

A Rulebook for Arguments Fifth Edition Anthony Weston A Rulebook for Arguments Fifth Edition  Anthony Weston A Rulebook for Arguments Fifth Edition Hackett Publishing Company, Inc. Indianapolis/Cambridge Copyright © 2017 by Hackett...

A Rulebook for Arguments Fifth Edition Anthony Weston A Rulebook for Arguments Fifth Edition  Anthony Weston A Rulebook for Arguments Fifth Edition Hackett Publishing Company, Inc. Indianapolis/Cambridge Copyright © 2017 by Hackett Publishing Company, Inc. All rights reserved Printed in the United States of America 20 19 18 17   1 2 3 4 5 6 7 For further information, please address Hackett Publishing Company, Inc. P.O. Box 44937 Indianapolis, Indiana 46244-0937 www.hackettpublishing.com Cover art and interior design by Elizabeth L. Wilson Composition by Integrated Composition Systems Library of Congress Cataloging-in-Publication Data Names: Weston, Anthony, 1954– author. Title: A rulebook for arguments / Anthony Weston. Description: Fifth edition. | Indianapolis ; Cambridge : Hackett Publishing Company, Inc., 2017. | Includes bibliographical references. Identifiers: LCCN 2017027845 | ISBN 9781624666544 (pbk.) | ISBN 9781624666872 (cloth) Subjects: LCSH: Reasoning. | Logic. | English language—Rhetoric. Classification: LCC BC177.W47 2017 | DDC 168—dc23 LC record available at https://lccn.loc.gov/2017027845 Adobe PDF ebook ISBN: 978-1-62466-655-1  Contents Preface ix Note to the Fifth Edition x Introduction xiii I. Short Arguments: Some General Rules 1 1. Resolve premises and conclusion 1 2. Unfold your ideas in a natural order 3 3. Start from reliable premises 4 4. Be concrete and concise 5 5. Build on substance, not overtone 6 6. Use consistent terms 7 II. Arguments by Example 9 7. Use more than one example 10 8. Use representative examples 11 9. Background rates are often crucial 13 10. Statistics need a critical eye 14 11. Reckon with counterexamples 16 III. Arguments by Analogy 19 12. Analogies require relevantly similar examples 20 IV. Arguments from Authority 23 13. Cite your sources 24 14. Seek informed sources 25 v vi Contents 15. Seek impartial sources 27 16. Cross-check sources 28 17. Build your Internet savvy 30 IV. Arguments about Causes 33 18. Causal arguments start with correlations 33 19. Correlations may have alternative explanations 34 20. Work toward the most likely explanation 36 21. Expect complexity 38 VI. Deductive Arguments 39 22. Modus ponens 40 23. Modus tollens 41 24. Hypothetical syllogism 42 25. Disjunctive syllogism 43 26. Dilemma 44 27. Reductio ad absurdum 45 28. Deductive arguments in multiple steps 47 VII. Extended Arguments 51 29. Explore the issue 51 30. Spell out basic ideas as arguments 53 31. Defend basic premises with arguments of their own 55 32. Reckon with objections 57 33. Explore alternatives 58 VIII. Argumentative Essays 61 34. Jump right in 61 35. Urge a definite claim or proposal 62  Contents vii 36. Your argument is your outline 63 37. Detail objections and meet them 65 38. Seek feedback and use it 66 39. Modesty, please! 67 IX. Oral Arguments 69 40. Ask for a hearing 69 41. Be fully present 70 42. Signpost energetically 71 43. Hew your visuals to your argument 72 44. End in style 73 X. Public Debates 75 45. Do argument proud 75 46. Listen, learn, leverage 76 47. Offer something positive 78 48. Work from common ground 80 49. At least be civil 82 50. Leave them thinking when you go 83 Appendix I: Some Common Fallacies 87 Appendix II: Definitions 95 D1. When terms are unclear, get specific 95 D2. When terms are contested, work from the clear cases 97 D3. Definitions don’t replace arguments 99 Resources 101  Preface This book is a brief introduction to the art of making arguments. It sticks to the bare essentials. I have found that students and writers often need just such a list of reminders and rules, not lengthy intro- ductory explanations. This book is therefore organized around spe- cific rules, illustrated and explained soundly but above all briefly. It is not a textbook but a rulebook. Instructors too, I have found, often wish to assign such a rule- book, a treatment that students can consult and understand on their own and that therefore does not claim too much class time. Here again, it is important to be brief—the point is to help students get on with their actual arguments—but the rules must be stated with enough substance that an instructor can simply refer a student to Rule 6 or Rule 16 rather than give an entire explanation each time it is needed. Brief but self-sufficient—that is the fine line I have tried to follow. This rulebook also can be used in a course that gives critical at- tention to arguments. It will need to be supplemented with exercises and more examples, but many texts are already available that consist largely or wholly of such exercises and examples. Those texts, how- ever, also need to be supplemented—with what this rulebook offers: simple rules for putting good arguments together. We do not want our students to come out of critical thinking courses knowing only how to shoot down (or just at) selected fallacies. Critical thinking can be practiced in a far more constructive spirit. This book is one attempt to suggest how. ix  Note to the Fifth Edition Rulebook continues to find a wide use in a variety of schools, from high school to law school, and in other settings too. The world continues to change as well. In this fifth edition there are several corresponding changes. Most notably, I have added a new final chapter, “Public De- bates,” which repositions a few of the old rules but mostly adds new ones. The state of our public debate at the moment is pretty sorry, and while this surely has many causes, a better understanding of the etiquette and the ethics of good public debate should help. Six short rules—but what a difference they might make! Smaller changes include a number of updated examples, drawing on a wider and more contemporary range of sources. Goodbye Ein- stein, hello Beyoncé. This edition is a little fresher, a little tighter, a bit more humorous. Some of the rules have acquired punchy subti- tles. This is no time to be timid about the need for good arguments and better ways of arguing, either, so you may find this new edition somewhat edgier as well. For instructors and students who may be interested, I am happy to add that a companion textbook to A Rulebook for Arguments is now available. David Morrow and I have written it ourselves: A Workbook for Arguments. Workbook includes the entire Rulebook, but between each section of this brief guide, Workbook interpolates further expla- nations and extensive examples and exercises, with a thorough selec- tion of sample answers as well. Many thanks to Professor Morrow for convincing me and Hackett Publishing Company of the need for and appeal of such a textbook, and then doing the lion’s share of the work on it, carrying it now through two editions (first edition 2013; second edition 2016). David’s insights and suggestions have helped shape this new edition of Rulebook as well. Among related changes is that a few of the more challenging ex- amples and themes in previous editions of Rulebook, most notably philosopher David Hume’s challenges to some of the usual argu- ments for the existence of God, are migrating to Workbook, where they can be treated in more depth. In many ways, Workbook is a x  Note to the Fifth Edition xi natural follow-up to Rulebook, even if you are not in a class that re- quires it. We hope you will have a look. By now it is a long list of colleagues, students, family members, and friends who have contributed thoughts, suggestions, or provo- cations to this and previous editions of Rulebook. This time around I would like to single out Deborah Wilkes, president and publisher, and her colleagues at Hackett Publishing Company, whose stal­ wart support and gentle encouragement has made both Rulebook and Workbook continuously enjoyable and superlatively produced projects. My continuing gratitude to you all! Anthony Weston July 2017  Introduction What’s the point of arguing? Many people think that arguing is simply stating their prejudices in a new form. This is why many people also think that arguments are unpleasant and pointless. One dictionary definition for “argu- ment” is “disputation.” In this sense we sometimes say that two peo- ple “have an argument”: a verbal fistfight. It happens often enough. But it is not what arguments really are. In this book, “to give an argument” means to offer a set of reasons or evidence in support of a conclusion. Here an argument is not sim- ply a statement of certain views, and it is not simply a dispute. Argu- ments are efforts to support certain views with reasons. Arguments in this sense are not pointless. In fact, they are essential. Argument is essential, in the first place, because it is a way of finding out which views are better than others. Not all views are equal. Some conclusions can be supported by good reasons. Others have much weaker support. But often we don’t know which are which. We need to give arguments for different conclusions and then assess those arguments to see how strong they really are. Here argument is a means of inquiry. Some philosophers and ac- tivists have argued, for instance, that the factory farming of animals for meat causes immense suffering to animals and is therefore unjus- tified and immoral. Are they right? We can’t necessarily tell just by consulting our current opinions. Many issues are involved—we need to examine the arguments. Do we have moral obligations to other species, for instance, or is only human suffering really bad? How well can humans live without meat? Some vegetarians have lived to very old ages. Does this show that vegetarian diets are healthier? Or is it irrelevant when you consider that some nonvegetarians also have lived to very old ages? (You might make some progress by asking xiii xiv Introduction whether vegetarians live to old age at a higher rate.) Or might health- ier people tend to become vegetarians, rather than vice versa? All of these questions need to be considered carefully, and the answers are not clear in advance. Argument is essential for another reason too. Once we have a­ rrived at a conclusion that is well supported by reasons, we use arguments to explain and defend it. A good argument doesn’t merely repeat conclusions. Instead it offers reasons and evidence so that other peo- ple can make up their minds for themselves. If you become convinced that we should indeed change the way we raise and use animals, for example, you must use arguments to explain how you arrived at your conclusion. That is how you will convince others: by offering the reasons and evidence that convinced you. It is not a mistake to have strong views. The mistake is to have nothing else. Argument grows on you Typically we learn to “argue” by assertion. That is, we tend to start with our conclusions—our desires or opinions—without a whole lot to back them up. And it works, sometimes, at least when we’re very young. What could be better? Real argument, by contrast, takes time and practice. Marshaling our reasons, proportioning our conclusions to the actual evidence, considering objections, and all the rest—these are acquired skills. We have to grow up a little. We have to put aside our desires and our opinions for a while and actually think. School may help—or not. In courses concerned with teaching ever-larger sets of facts or techniques, students are seldom encour- aged to ask the sorts of questions that arguments answer. Sure, our Constitution mandates the Electoral College—that’s a fact—but is it still a good idea? (For that matter, was it ever a good idea? What were the reasons for it, anyway?) Sure, many scientists believe that there is life elsewhere in the universe, but why? What’s the argu- ment? Reasons can be given for different answers. In the end, ideally, you will not only learn some of those reasons but also learn how to weigh them up—and how to seek out more yourself.  Introduction xv Mostly, again, it takes time and practice. This book can help! Moreover, the practice of argument turns out to have some attrac- tions of its own. Our minds become more flexible, open-ended, and alert. We come to appreciate how much difference our own critical thinking can really make. From everyday family life to politics, sci- ence, philosophy, and even religion, arguments are constantly of- fered to us for our consideration, and we may in turn offer back our own. Think of argument as a way to make your own place within these unfolding, ongoing dialogues. What could be better than that? Outline of this book This book begins by discussing fairly simple arguments, moving then to extended arguments and their use in essays, oral presenta- tions, and finally to public debates. Chapters I–VI are about composing and assessing short argu- ments. Short arguments simply offer their reasons and evidence briefly, usually in a few sentences or a paragraph. We begin with short arguments for several reasons. First, they are common: in fact so common that they are part of every day’s conversation. Second, longer arguments are usually elaborations of short arguments, or a series of short arguments linked together. If you learn to write and assess short arguments first, then you can extend your skills to longer arguments in essays or presentations. A third reason for beginning with short arguments is that they are the best illustrations both of the common argument forms and of the typical mistakes in arguments. In longer arguments, it can be harder to pick out the main points—and the main problems. Therefore, although some of the rules may seem obvious when first stated, re- member that you have the benefit of a simple example. Other rules are hard enough to appreciate even in short arguments. Chapter VII guides you into sketching and then elaborating an extended argument, considering objections and alternatives as you do. Chapter VIII guides you from there into writing an argumen­ tative essay. Chapter IX then adds rules specifically about oral presen­tation, and Chapter X about public debate. Again, all of these xvi Introduction chapters depend on Chapters I–VI, since extended arguments like these essentially combine and elaborate the kinds of short arguments that Chapters I–VI discuss. Don’t skip ahead to the later chapters, then, even if you come to this book primarily for help writing an ­essay or doing a presentation. The book is short enough that you can read it through from the beginning, so that when you arrive at those later chapters you will have the tools you need to use them well. In- structors might wish to assign Chapters I–VI early in the term and Chapters VII–X when the time comes for essays and public presen- tations and debates. Two appendices close out the book. The first is a listing of fallacies: types of misleading arguments that are so tempting and common, they even have their own names. The second offers three rules for constructing and evaluating definitions. Use them when you need them!  I Short Arguments Some General Rules Arguments begin by marshaling reasons and organizing them in a clear and fair way. Chapter I offers general rules for composing short arguments. Chapters II–VI discuss specific kinds of short arguments. 1 Resolve premises and conclusion The very first step in making an argument is to ask yourself what you are trying to prove. What is your conclusion? Remember that the conclusion is the statement for which you are giving reasons. The statements that give your reasons are your premises. Let’s say that you want to persuade your friends (or children, or parents, or...) to eat more beans. Probably this does not seem like the world’s most promising proposition, or the most important either. But it is a good first illustration—and diet does matter! Let’s con- sider how you might make such an argument. You have your conclusion: we should eat more beans. That is your belief. But why? What are your reasons? You may need to state them for yourself, for clarity first of all, and then to check that they really are good reasons. Certainly you have to state good reasons clearly if you expect others to agree or to change how they eat. So again: What are your reasons? One main premise probably is that beans are healthy: higher in fibers and protein and lower in fat and cholesterol than what most people eat now. So, properly supple- mented, a diet of more beans could lead to a longer and more active life. You may not want to assume that your friends or family have heard, or really appreciated, this reason before—at least it is useful to be reminded. 1 2 1. Resolve premises and conclusion To get people motivated, it would be helpful to add another main premise as well. Since beans are often stereotyped as boring, why not also argue that bean dishes actually can be varied and excit- ing? Give some examples, your own favorite bean dishes maybe: spicy black bean taco fillings, for instance, and hummus (made from gar- banzo beans). Now you’ve got an argument—good solid reasons for a clear conclusion. Even jokes can be arguments, though the reasons may seem silly. Living on earth may be tough, but it includes a free ride around the sun every year.1 Getting a free ride around the sun is not the sort of reason you nor- mally expect for bearing up when life gets tough. That’s what makes the joke funny. But it is still a reason: an attempt to justify the claim that life isn’t quite so bad as it may sometimes seem. It’s a funny argument. In Rule 1—Resolve premises and conclusion—the word “resolve” has two related meanings. One is to distinguish them. Your reasons are different from your conclusion: keep them clearly separate. Get- ting a free ride around the sun is a distinct idea from bearing up when life gets tough, and it logically comes first. It’s a premise. Being better able to bear up might be something that follows. It’s a conclusion. Once you have distinguished your premises and conclusion, be sure that both are claims that you want to commit to. This is the other meaning of “resolve.” If so, proceed. If not, change them! In any case, being clear to yourself is necessary before you can be clear to anyone else. This book offers you a ready list of different forms that arguments can take. Use this list to develop your premises. To defend a gener- alization, for instance, check Chapter II. It will remind you that you need to give a series of examples as premises, and it will tell you what sorts of examples to look for. If your conclusion requires a de- ductive argument like those explained in Chapter VI, the rules out- lined in that chapter will tell you what types of premises you need. You may have to try several different arguments before you find one that works well. 1. Anonymous, Cool Funny Quotes, http://coolfunnyquotes.com. Accessed 2/6/17.  2. Unfold your ideas in a natural order 3 2 Unfold your ideas in a natural order Arguments move. Reasons and evidence lead to conclu- sions. But, like any other form of movement, arguments may be grace­ful or clumsy, sharp or confused, clean or muddled. You want clarity and efficiency—even grace, if you can manage it. Take the argument about beans once more. If you were now going to write your argument out, how might you do it? One good way would be this: We should eat more beans. One reason is that beans are healthy. They are higher in fibers and protein and lower in fat and cholesterol than what most people eat now. Meanwhile, bean dishes can be quite varied and exciting too. Think of spicy black bean taco fillings or hummus. Each sentence in this passage prepares the way for the next one, and then the next one steps smoothly up to bat. The argument be- gins by stating its conclusion. This invites stating premises in turn, and the argument obliges by immediately stating a main premise, and then giving a brief reason for it in turn, explaining why beans are healthy. Then it offers the other main premise and its examples. The argument could be laid out in different ways—for example, the sec- ond main premise could be first, and/or the conclusion could be drawn at the end rather than the beginning—but either way, each part is in a good place. Getting an argument to unfold in this smooth way is an accom- plishment, especially as arguments get more detailed and complex. It’s not easy to work out the right place for each part—and plenty of wrong places are usually available. For example, suppose we wrote the argument like this instead: Think of spicy black bean taco fillings or hummus. Beans are higher in fibers and protein and lower in fat and cholesterol than what most people eat now. Bean dishes can be quite var- ied and exciting. We should eat more beans. Beans are healthy. 4 3. Start from reliable premises These are the same premises and conclusion, but they are in a dif- ferent order, and the passage leaves out the signposts and transition words that help readers identify premises and conclusions (such as “one reason is that...”). The result is that the argument is totally garbled. The examples for the main premises, like how tasty bean dishes can be, are scattered through the passage rather than cited right next to the statement of those premises. You have to read the passage twice just to be sure what the conclusion is. Don’t count on your readers to be so patient. Expect to rearrange your argument several times to find the most natural order. Again, the rules offered in this book should help. You can use them to figure out not only what kinds of premises you need but also how to arrange them in the best order. 3 Start from reliable premises No matter how well you argue from premises to conclu- sion, your conclusion will be weak if your premises are weak. Nobody in the world today is really happy. Therefore, it seems that human beings are just not made for happiness. Why should we expect what we can never find? The premise of this argument is the statement that nobody in the world today is really happy. Sometimes, on certain rainy afternoons or in certain moods, this may almost seem true. But ask yourself if this premise really is plausible. Is nobody in the world today really happy? Ever? What about that free ride around the sun every year? At the very least, this premise needs some serious defense, and very likely it is just not true. This argument cannot show, then, that human beings are not made for happiness or that you or I should not expect to be happy. Sometimes it is easy to start from reliable premises. You may have well-known examples at hand or reliable sources that are clearly in agreement. Other times it is harder. If you are not sure about the reliability of a premise, you may need to do some research and/or  4. Be concrete and concise 5 give an argument for the premise itself (see Rule 31 for more on this point). If you find you cannot argue adequately for your premise(s), then, of course, you need to try some other premise! 4 Be concrete and concise Avoid abstract, vague, and general terms. “We hiked for hours in the sun” is a hundred times better than “It was an extended period of laborious exertion.” Be concise too. Airy elaboration just loses everyone in a fog of words. NO: Regularly turning in for the night at an hour that precedes the time at which most of your compatriots go to bed, com- bined with the practice of awakening at an hour that is earlier than the hour at which most others arise, will tend to the acquisition of such desirable personal traits as a resilient physi- cal constitution, a comfortably well-established financial sit- uation, and the sort of intellectual abilities and capacity for sagacious discernment and judgment that tend to be condu- cive to earning the respect of others. YES: Early to bed and early to rise makes a man healthy, wealthy, and wise. The “No” version might overdo it just a bit (you think?), but you see the point. Ben Franklin’s rhyme and rhythm help too, but the most important thing is that his words are sharp, simple, and few. 6 5. Build on substance, not overtone 5 NO: Build on substance, not overtone Offer actual reasons; don’t just play on the overtones of words. Having so disgracefully allowed her once-proud passenger railroads to fade into obscurity, America is honor-bound to restore them now! This is supposed to be an argument for restoring (more) passenger rail service. But it offers no evidence for this conclusion whatsoever, just some emotionally loaded words—shopworn words, too, like a politician on automatic. Did passenger rail “fade” because of some- thing “America” did or didn’t do? What was “disgraceful” about this? Many “once-proud” institutions outlive their times, after all— we’re not obliged to restore them all. What does it mean to say America is “honor-bound” to do this? Have promises been made and broken? By whom? Much can be said for restoring passenger rail, especially in this era when the ecological and economic costs of highways are becom- ing enormous. The problem is that this argument does not say it. It lets the emotional charge of the words do all the work, and therefore really does no work at all. We’re left exactly where we started. Over- tones may sometimes persuade even when they shouldn’t, of course— but remember, here we are looking for actual, concrete evidence. Likewise, do not try to make your argument look good by using emotionally loaded words to label the other side. Generally, people advocate a position for serious and sincere reasons. Try to figure out their view—try to understand their reasons—even if you disagree entirely. For example, people who question a new technology are probably not in favor of “going back to the caves.” (What are they in favor of? Maybe you need to ask.) Likewise, a person who believes in evolution is not claiming that her grandparents were monkeys. (And again: what does she think?) In general, if you can’t imagine how anyone could hold the view you are attacking, you probably just don’t understand it yet.  6. Use consistent terms 7 6 Use consistent terms Short arguments normally have a single theme or thread. They carry one idea through several steps. Therefore, couch that idea in clear and carefully chosen terms, and mark each new step by using those very same terms again. In their classic composition handbook, The Elements of Style, Wil- liam Strunk and E. B. White cite Jesus’s famous Beatitudes as a compelling illustration of what they call “parallel construction” or “expressing coordinate ideas in similar form.” Blessed are the poor in spirit: for theirs is the kingdom of Heaven. Blessed are those who mourn: for they will be comforted. Blessed are the meek: for they will inherit the earth... (Mat- thew 5:3–5) “Blessed are the X: for Y” is the formula. It is not rephrased in each case, like “Also, those who are X will be consecrated, because Y.” Instead, each sentence has exactly the same structure and exactly the same phrasing. Do the same for your arguments. NO: When you learn to care for a pet, you learn to attend to the needs of a dependent creature. Watching and responding carefully when a cat or a dog needs you, your ability to recog- nize needs and adjust your behavior accordingly can improve toward young children as well. Becoming a more responsive keeper of domestic animals can therefore enhance your fa- milial caregiving skills too. Huh? Each sentence may be fairly clear by itself, but the connections between them are totally lost in the underbrush—interesting under- brush, maybe, but too thick for moving effectively. (Remember, ar- guments need to move!) 8 6. Use consistent terms YES: When you learn to care for a pet, you learn to attend to the needs of a dependent creature. When you learn to attend to the needs of a dependent creature, you learn to be a better parent. Therefore, when you learn to care for a pet, you learn to be a better parent. The “Yes” version might not be stylish in a flowery way, but it more than makes up for that by being absolutely crystal clear. One simple feature makes the difference: the “No” version uses a new phrase for each key idea every time the idea recurs—for example, “When you learn to care for a pet” is described again in the “No” version’s conclusion as “Becoming a more responsive keeper of domestic animals”—whereas the “Yes” argument carefully and exactly repeats its key terms. If you are concerned about style—as sometimes you should be, of course—then go for the tightest argument, not the most flowery. MOST CONCISE: When you learn to care for a pet, you learn to attend to the needs of a dependent creature, and therefore in turn learn to be a better parent.  II Arguments by Example Some arguments offer one or more examples in support of a gen­ eralization. Women in earlier times were married very young. Juliet in Shakespeare’s Romeo and Juliet was not even fourteen years old. In the Middle Ages, thirteen was the normal age of mar- riage for a Jewish woman. And during the Roman Empire, many Roman women were married at age thirteen or younger. This argument generalizes from three examples—Juliet, Jewish women in the Middle Ages, and Roman women during the Roman Empire—to “many” or most women in earlier times. To show the form of this argument most clearly, we can list the premises sepa- rately, with the conclusion on the “bottom line”: Juliet in Shakespeare’s play was not even fourteen years old. Jewish women during the Middle Ages were normally mar- ried at thirteen. Many Roman women during the Roman Empire were mar- ried at age thirteen or younger. Therefore, women in earlier times were married very young. It is helpful to write short arguments in this way when we need to see exactly how they work. When do premises like these adequately support a generalization? One requirement, of course, is that the examples be accurate. Re- member Rule 3: start from reliable premises! If Juliet wasn’t around fourteen, or if most Roman or Jewish women weren’t married at thirteen or younger, then the argument is much weaker. If none of the premises can be supported, there is no argument at all. To check 9 10 7. Use more than one example an argument’s examples, or to find good examples for your own arguments, you may need to do some research. But suppose the examples are accurate. Even then, generalizing from them is a tricky business. The rules in this chapter offer a short checklist for assessing arguments by example. 7 Use more than one example A single example can sometimes be used for the sake of ­illustration. The example of Juliet alone might illustrate early mar- riage. But a single example offers next to no support for a general- ization. Juliet alone may just be an exception. One spectacularly mis­er­able billionaire does not prove that rich people in general are unhappy. One great meal at a new restaurant in town does not neces- sarily mean that its whole menu is first-rate. More than one example is needed. NO: Solar power is widely used. Therefore, renewable energy is widely used. Solar power is one form of renewable energy, but only one. What about others? YES: Solar power is widely used. Hydroelectric power has long been widely used. Windmills were once widely used and are becoming widely used again. Therefore, renewable energy is widely used. The “Yes” version may not be perfect (Rule 11 returns to it), but it certainly is more energetic, so to speak, than the “No” version.  8. Use representative examples 11 In a generalization about a small set of things, the strongest argu- ment should consider all, or at least many, of the examples. A gener- alization about your siblings should consider each of them in turn, for instance, and a generalization about all the planets in the solar system can do the same. Generalizations about larger sets of things require picking out a sample. We cannot list all women in earlier times who married young. Instead, our argument must offer a few women in earlier times as a sample of all women in earlier times. How many examples are required depends partly on how representative they are, a point the next rule takes up. It also depends partly on the size of the set being generalized about. Large sets usually require more examples. The claim that your town is full of remarkable people requires more evi- dence than the claim that, say, your friends are remarkable people. Depending on how many friends you have, even just two or three examples might be enough to establish that your friends are remark- able people; but, unless your town is tiny, many more examples are required to show that your town is full of remarkable people. 8 Use representative examples Even a large number of examples may misrepresent the set of things being generalized about. Do all insects bite, for exam- ple? Sure, we can think of lots of insects that do, like mosquitoes and black flies, and naturally those are the examples we think of first. After all, we are bugged by them! We may have to consult a biology textbook or a good online source to remember how many kinds of insects there are that don’t bite—which is most of them, actually: moths, praying mantis, ladybugs, (most) beetles, and so on. Likewise, a large number of examples of ancient Roman women establishes very little about women generally, since ancient Roman women are not necessarily representative of other women in earlier times. If we want to make a sweeping claim about women in earlier times, the argument needs to consider women from other early times and from other parts of the world as well. 12 8. Use representative examples It is easy to overlook how unrepresentative—often wildly unrep- resentative—our personal “samples” often are. Actually, very few if any of us really know a representative sample of other people. Yet we constantly generalize about other people as a group, such as when we make claims about “human nature,” or even how our town might vote in the next election. NO: Everyone in my neighborhood favors the School Bond. There- fore, the School Bond is sure to pass. This argument is weak because single neighborhoods seldom repre- sent the voting population as a whole. A well-to-do neighborhood may favor a cause unpopular with everyone else. Student wards in university towns regularly are carried by candidates who do poorly elsewhere. Besides, we do not always have good evidence even about the views held in a specific neighborhood. The set of people eager to display their political preferences to the world in yard signs, for example, is unlikely to be a representative cross-section of the neigh- borhood as a whole. A good argument that “The School Bond is sure to win” requires a representative sample of the entire voting population. It is not easy to construct such a sample. In fact, it usually takes professional help, and even professional pollsters regularly predict elections in- correctly. Telephone pollsters used to call landlines, for example, because cell phone numbers are not as publicly accessible; but only certain demographic groups still have landlines, and they are increas- ingly unrepresentative. In general, look for the most accurate cross-section you can find of the population being generalized about. If you want to know what students think about some subject at your university, don’t just ask your friends or generalize from what you hear in class. Unless you have quite a range of friends and take a wide range of classes, your per- sonal sample is very unlikely to accurately mirror the whole student body. Similarly, if you want to know what people in other countries think about the United States, don’t just ask foreign tourists—for they, of course, are the ones who chose to come here. A careful look  9. Background rates are often crucial 13 at a diverse range of foreign media should give you a more represen- tative picture. When your sample is people, an even more basic point is that no one should be able to self-select for it. This immediately disqualifies almost all online or mail-in polls to which individuals can decide whether to respond or not. Again, the set of people who are willing or eager to express their opinions is almost certainly not representa- tive of the whole population, but are the people more likely to have strong opinions—or a lot of time on their hands. It may be interest- ing to know what that group thinks anyway, but not because they necessarily speak for anyone but themselves. 9 Background rates are often crucial To persuade you that I am a first-rate archer, it is not enough to show you a bull’s-eye I have made. You should ask (po- litely, to be sure), “Yes, but how many times did you miss?” Getting a bull’s-eye in one shot tells quite a different story than getting a bull’s-eye in, say, a thousand, even though in both cases I genuinely do have a bull’s-eye to my name. You need a little more data. Leon’s horoscope told him that he would meet a vivacious new stranger, and lo and behold he did! Therefore, horoscopes are reliable. Dramatic as such an example may be, the problem is that we are only looking at one case in which a horoscope came true. To properly evaluate this evidence, we need to know something else as well: how many horoscopes didn’t come true. When I survey my classes, we can usually find a few Leons out of twenty or thirty students. It’s a fun moment. But the other nineteen or twenty-nine horoscopes go nowhere. A kind of prediction that comes true only once out of twenty or thirty tries is hardly reliable—it’s just lucky once in a while. It may have some dramatic successes, like my archery, but its success rate may still be abysmal. To evaluate the reliability of any argument featuring a few vivid examples, then, we need to know the ratio between the number of 14 10. Statistics need a critical eye “hits,” so to speak, and the number of tries. It’s a question of repre- sentativeness again. Are the featured examples the only ones there are? Is the rate impressively high or low? This rule is widely applicable. Today, many people live in fear of crime, or constantly attend to stories of shark attacks, terrorism, or other dramatic events. Of course these things are awful when they occur, but the probability of any of them actually happening to any given individual—say, the shark attack rate—is extremely low. Crime rates continue to go down. No doubt we are preoccupied with the exceptions because they are constantly featured on TV and in the news. This does not mean that they are actually representative. The same goes, by the way, for desired things, like winning the lottery. Any individual’s chance of winning—that is, the winning rate—is so low as to be basically nil, but we seldom see the hundreds of thousands of losers, just the one or few winners raking in the money. So we wildly overestimate the background rates, and imagine that with the next lottery ticket pur- chase, we may be the one. Save your money, friends. Background rates make all the difference! 10 Statistics need a critical eye You cannot “prove anything with numbers”! Some people see numbers—any numbers—in an argument and con- clude from that fact alone that it must be a good argument. Statistics seem to have an aura of authority and definiteness (and did you know that 88 percent of doctors agree?). In fact, though, numbers take as much critical thinking as any other kind of evidence. Don’t turn off your brain! After an era when some athletic powerhouse universities were accused of exploiting student athletes, leaving them to flunk out once their eligibility expired, college athletes are now graduating at higher rates. Many schools are now graduating more than 50 percent of their athletes.  10. Statistics need a critical eye 15 Fifty percent, eh? Pretty impressive! But this figure, at first so per- suasive, does not really do the job it claims to do. First, although “many” schools graduate more than 50 percent of their athletes, it appears that some do not—so this figure may well exclude the most exploitative schools that really concerned people in the first place. The argument does offer graduation rates. But it would be useful to know how a “more than 50 percent” graduation rate compares with the graduation rate for all students at the same institutions. If it is significantly lower, athletes may still be getting the shaft. Most importantly, this argument offers no reason to believe that college athletes’ graduation rates are actually improving, because no comparison to any previous rate is offered! The conclusion claims that the graduation rate is now “higher,” but without knowing the previous rates it is impossible to tell. Numbers may offer incomplete evidence in other ways too. Rule 9, for example, tells us that knowing background rates may be cru- cial. Correspondingly, when an argument offers rates or percentages, the relevant background information usually must include the num- ber of examples. Car thefts on campus may have doubled, but if this means that two cars were stolen rather than one, there’s not much to worry about. Another statistical pitfall is over-precision: Every year this campus wastes 412,067 paper and plastic cups. It’s time to switch to reusable cups! I’m all for ending waste too, and I’m sure the amount of campus waste is huge. But no one really knows the precise number of cups wasted—and it’s extremely unlikely to be exactly the same every year. Here the appearance of exactness makes the evidence seem more authoritative than it really is. Be wary, also, of numbers that are easily manipulated. Pollsters know very well that the way a question is asked can shape how it is answered. These days we are even seeing “polls” that try to change people’s minds about, say, a political candidate, just by asking loaded questions (“If you were to discover that she is a liar and a cheat, how would that change your vote?”). Then too, many apparently “hard” statistics are actually based on guesswork or extrapolation, such as 16 11. Reckon with counterexamples data about semi-legal or illegal activities. Since people have a major motive not to reveal or report things like drug use, under-the-­counter transactions, hiring illegal aliens, and the like, beware of any con­fi­ dent generalizations about how widespread they are. Yet again: If kids keep watching more TV at current rates, by 2025 they’ll have no time left to sleep! Right, and by 2040 they’ll be watching thirty-six hours a day. Extra­ polation in such cases is perfectly possible mathematically, but after a certain point it tells you nothing. 11 Reckon with counterexamples Counterexamples are examples that contradict your generalization. No fun—maybe. But counterexamples actually can be a generalizer’s best friends, if you use them early and use them well. Exceptions don’t “prove the rule”—quite the contrary, they threaten to disprove it—but they can and should prompt us to refine it. Therefore, seek out counterexamples early and systematically. It is the best way to sharpen your own generalizations and to probe more deeply into your theme. Consider this argument once again: Solar power is widely used. Hydroelectric power has long been widely used. Windmills were once widely used and are becoming widely used again. Therefore, renewable energy is widely used. The examples here certainly do help to show that many renewable energy sources are widely used: sun, wind, and rain. However, as soon as you start thinking about counterexamples instead of just more ex- amples, you may find that the argument somewhat overgeneralizes.  11. Reckon with counterexamples 17 Are all renewables widely used? Look up the definition of “re­ newable energy” and you will find that there are other types as well, such as the tides and geothermal energy (the internal heat of the earth). And these, for better or worse, are not so widely used. They aren’t available everywhere, for one thing, and may be difficult to harness even when available. When you think of counterexamples to a generalization that you want to defend, then you need to adjust your generalization. If the re­ newable energy argument were yours, for instance, you might change the conclusion to “Many forms of renewable energy are widely used.” Your argument still hits the high points, so to speak, while it acknow­ ledges limits and the possibility for improvement in some areas. Counterexamples should prompt you to think more deeply about what you actually want to say. For example, maybe your interest in arguing about renewables is to try to show that there are ready and workable alternatives to the usual non-renewable sources. If that is your aim, you don’t necessarily need to argue that all renewables are widely used. It is enough that some are. You might even urge that the ones that are less widely used be better developed. Or, instead of arguing that every renewable source is or could be widely used, you might really want to be arguing that every (or most every?) place has at least some renewable source available to it, though there may be different sources in different places. This is a quite different and more subtle claim than the original, and gives your thinking some interesting room to move. (Might this argument have counterexamples too? I leave that question for you.) Ask yourself about counterexamples when you are assessing others’ arguments as well as evaluating your own. Ask whether their conclusions might have to be revised and limited, or rethought in more subtle and complex directions. The same rules apply both to others’ arguments and to yours. The only difference is that you have a chance to correct your overgeneralizations yourself.  III Arguments by Analogy There is an exception to Rule 7 (“Use more than one example”). Arguments by analogy, rather than multiplying examples to support a generalization, argue from one specific example to another, reason- ing that because the two examples are alike in many ways, they are also alike in one further specific way. Valentina Tereshkova, Russian astronaut and first woman in space, famously quipped that If women can be railroad workers in Russia, why can’t they fly in space? Russian women are as capable of demanding physical and technical work as men, Tereshkova is arguing, and as devoted to their work and their country—as proved by the example of female railroad workers. Therefore, women should also make fine astronauts. Spelled out, the argument looks like this: Women have proved themselves to be capable railroad work- ers in Russia. Being a railroad worker is like being an astronaut (because they both make extreme physical and technical demands). Therefore, women can be capable astronauts as well. Notice the italicized word “like” in the second premise. When an argument stresses the likeness between two cases, it is very probably an argument from analogy. 19 20 12. Analogies require relevantly similar examples 12 Analogies require relevantly similar examples How do we evaluate arguments by analogy? The first premise of an argument by analogy makes a claim about the example used as an analogy. Remember Rule 3: make sure this premise is true. Tereshkova’s argument could not even get off the ground, so to speak, if women had not proved themselves to be ca- pable railroad workers in Russia. The second premise in arguments by analogy claims that the example in the first premise is like the example about which the ar- gument draws a conclusion. Evaluating this premise requires us to ask how relevantly similar the two cases are. They do not have to be similar in every way. After all, being an astronaut is very different than working on the railroad. Trains don’t fly, for example—or when they do, the story does not have a happy ending. Astronauts better not wield sledgehammers. But argument by analogy only requires relevant similarities. Technical skill and physical strength and stamina seem to be Tereshkova’s real themes. Both astronauts and railroad workers require a lot of both. So how relevantly similar, in the end, is Tereshkova’s analogy? For modern astronauts, you might think that sheer physical stamina is less relevant than skill at running experiments and making scien- tific observations—skills not necessarily related to being a good rail- road worker. In Tereshkova’s time, however, physical strength and stamina were much more important, as was body size: the early cap- sules were quite small and actually suited women’s physiques better. The other key factor was that the early Russian astronauts had to eject from their capsule and parachute to the ground at the end of their missions—and Tereshkova was a champion parachutist. This was probably the key factor, and is related to strength and stamina, though not to railroad work. Tereshkova’s analogy partially succeeds, then, especially for her time, though it is less persuasive now. But of course, since there have now been many successful female astronauts, it is also less necessary.  12. Analogies require relevantly similar examples 21 Here is a more challenging argument from analogy. An interesting switch was pulled in Rome yesterday by Adam Nordwell, an American Chippewa chief. As he descended his plane from California dressed in full tribal regalia, Nordwell announced in the name of the American Indian people that he was taking possession of Italy “by right of discovery” in the same way that Christopher Columbus did in America. “I proclaim this day the day of the discovery of Italy,” said Nord­ well. “What right did Columbus have to discover Amer­ica when it had already been inhabited for thousands of years? The same right I now have to come to Italy and proclaim the discovery of your country.”2 Nordwell is suggesting that his “discovery” of Italy is like Colum- bus’s “discovery” of America in at least one important way: both Nordwell and Columbus claimed a country that already had been inhabited by its own people for centuries. Thus, Nordwell insists that he has as much “right” to claim Italy as Columbus had to claim America. But, of course, Nordwell has no right at all to claim Italy. It follows that Columbus had no right at all to claim America. Nordwell has no right to claim Italy for another people, let alone “by right of discovery” (because Italy has been inhab- ited by its own people for centuries). Columbus’s claim to America “by right of discovery” is like Nordwell’s claim to Italy (America, too, had been inhabited by its own people for centuries). Therefore, Columbus had no right to claim America for an- other people, let alone “by right of discovery.” How good is Nordwell’s analogy? Obviously, twentieth-century Italy is not just like fifteenth-century America. Italy is known to every twentieth-century schoolchild, whereas America was unknown to much of the world in the fifteenth century. Nordwell is not an ex- plorer, and a commercial jet is not the Santa Maria. But are these differences relevant to Nordwell’s analogy? Nordwell simply means to remind us that it is senseless to claim a country already inhabited 2. Miami News, 23 September 1973. 22 12. Analogies require relevantly similar examples by its own people. Whether that land is known to the world’s school- children, or how the “discoverer” arrived there, is not important. The more appropriate reaction might have been to try to establish diplomatic relations, as we would try to do today if somehow the land and people of Italy had just been discovered. That’s Nordwell’s point, and, taken in that way, his analogy makes a good (and unset- tling) argument.  IV Arguments from Authority No one can be an expert through direct experience on everything there is to know. We do not live in ancient times ourselves and there- fore cannot know first-hand at what age women tended to marry back then. Few of us have enough experience to judge which kinds of cars are safest in a crash. We do not know first-hand what is re- ally happening in Sri Lanka or the state legislature, or even in the average American classroom or street corner. Instead, we must rely on others—better-situated people, organizations, surveys, or refer- ence works—to tell us much of what we need to know about the world. We argue like this: X (a source that ought to know) says that Y. Therefore, Y is true. For instance: Dr. Aubrey de Grey says that people can live to be 1,000 years old. Therefore, people can live to be 1,000 years old. It’s a risky business, though. Supposed experts may be over­con­ fident (they’re human too), or may be misled, or may not even be reli- able. And everyone has biases, after all, even if innocent ones. Once again we must consider a checklist of standards that truly authorita- tive sources need to meet. 23 24 13. Cite your sources 13 Cite your sources Who’s got your back? Some factual assertions are so obvious or well known that they do not need support at all. It is usually not neces- sary to prove that the United States currently has fifty states or that Juliet loved Romeo. However, a precise figure for the current pop- ulation of the United States, say, does need a citation. Likewise, to develop Valentina Tereshkova’s argument for sending women to space, we’d need to find knowledgeable authorities to establish that women were indeed capable railroad workers in Russia. NO: I once read that there are cultures in which makeup and clothes are mostly men’s business, not women’s. If you’re arguing about whether men and women everywhere follow the gender roles familiar to us, this is a relevant example—a striking case of different gender roles. But few of us know anything about this sort of difference first-hand, and it will probably seem surprising and even unlikely to many people. To nail down the argument, then, you need to call upon a fully cited source. YES: Carol Beckwith’s classic study of “Niger’s Wodaabe” (Na- tional Geographic 164, no. 4 [October 1983], pp. 483–509) reports that among the West African Fulani peoples such as the Wodaabe, makeup and clothes are mostly men’s business. Citation styles vary—consult a handbook of style to find the a­ ppropriate format for your purposes—but all include the same basic information: enough so that others can easily find the source on their own.  14. Seek informed sources 25 14 Seek informed sources Who knows? Sources must be qualified to make the statements they make. Honda mechanics are qualified to discuss the merits of different Hondas, midwives and obstetricians are qualified to dis- cuss pregnancy and childbirth, teachers are qualified to discuss the state of their schools, and so on. These sources are qualified because they have the appropriate background and information. For the best information about global climate change, go to climatologists, not politicians. Where a source’s qualifications are not immediately clear, an ar- gument must explain them. Dr. Aubrey de Grey says that people can live to be 1,000 years old? Well, who is this Aubrey de Grey to expect us to believe him about such things? Here is an answer: He is a geron­ tologist who has developed detailed theories of the causes of aging (it is not inevitable, he argues) and possible preventive interventions, which he has laid out in several detailed books such as The Mito­ chondrial Free Radical Theory of Aging (Cambridge University Press, 1999), for which he was awarded a PhD in biology by Cambridge University in 2000. When someone like that says that people can live to be 1,000 years old—unlikely as it seems—it is not a random or unprofessional opinion. We should give him a serious hearing. As you explain your source’s qualifications, you can also add more direct evidence to your argument. Carol Beckwith’s classic study of “Niger’s Wodaabe” (Na- tional Geographic 164, no. 4 [October 1983], pp. 483–509) reports that among the West African Fulani peoples such as the Wodaabe, makeup and clothes are mostly men’s busi- ness. Beckwith and an anthropologist colleague lived with the Wodaabe for two years and observed many dances for which the men prepared by lengthy preening, face-painting, and teeth-whitening. (Her article includes many pictures too.) Wodaabe women watch, comment, and choose mates for their beauty—which the men say is the natural way. “Our beauty makes the women want us,” one says. 26 14. Seek informed sources Note that an informed source need not fit our general stereotype of an “authority”—and a person who fits our stereotype of an au- thority may not even be an informed source. If you’re checking out colleges, for instance, students are the best authorities, not admin- istrators or recruiters, because it’s the students who know what stu- dent life is really like. (Just be sure to find yourself a representative sample.) Note also that experts on one subject are not necessarily informed about every subject on which they offer opinions. Beyoncé is a vegan. Therefore, veganism is the best diet. Beyoncé may be a fabulous entertainer, but a diet expert she’s not. (Also, it is not entirely clear that she is a vegan, apparently.) Like- wise, just because someone can put the title “Doctor” before their name—that is, just because they have a PhD or MD in some field— does not mean that they are qualified to deliver opinions on any subject whatsoever. Sometimes we must rely on sources whose knowledge is better than ours but still limited in various ways. On occasion, the best information we can get about what is happening in a war zone or a political trial or inside a business or bureaucracy is fragmentary and filtered through journalists, international human rights organiza- tions, corporate watchdogs, and so on. If you must rely on a source that may have limited knowledge in this way, acknowledge the prob- lem. Let your readers or hearers decide whether imperfect authority is better than none at all. Truly informed sources rarely expect others to accept their con- clusions simply because they assert them. Good sources will offer at least some reasons or evidence—examples, facts, analogies, other kinds of arguments—to help explain and defend their conclusions. Beckwith, for example, offers photographs and stories from the years she lived with the Wodaabe. Thus, while we might need to take some of their specific claims on authority alone (for instance, we must take Beckwith at her word that she had certain experiences), we can expect even the best sources to offer arguments as well as their own judgments in support of their general conclusions. Look for those arguments, then, and look at them critically as well.  15. Seek impartial sources 27 15 Seek impartial sources People who have the most at stake in a dispute are usually not the best sources of information about the issues involved. Sometimes they may not even tell the truth. People accused in crim- inal trials are presumed innocent until proven guilty, but we seldom completely believe their claims of innocence without confirmation from impartial witnesses. Readiness to tell the truth as one sees it, though, is not always enough. The truth as one honestly sees it can still be biased. We tend to see what we expect to see. We notice, remember, and pass on in- formation that supports our point of view, but we may not be quite so motivated when the evidence points the other way. Therefore, look for impartial sources: people or organizations who do not have a stake in the immediate issue, and who have a prior and primary interest in accuracy, such as (some) university scientists or statistical databases. Don’t just rely on politicians or interest groups on one side of a major public question for the most accurate infor­ mation about the issues at stake. Don’t just rely on manufacturers’ advertisements for reliable information concerning their products. NO: My car dealer recommends that I pay $300 to rustproof my car. He should know; I guess I’d better do it. He probably does know, but he might not be entirely reliable, ­either. The best information about consumer products and services comes from independent consumer testing agencies, agencies not affili- ated with any manufacturer or provider but answering to consum- ers who want the most accurate information they can get. Do some research! YES: Experts at Consumer Reports say that rust problems have al- most vanished in modern cars due to better manufacturing, 28 16. Cross- check sources and advise that rustproofing is not needed (Consumer Re- ports, “Watch Out for These Car Sales Tricks,” http://www​.consumerreports.org/buying-a-car/car-sales-tricks/, 2 Feb- ruary 2017; and Sami Haaj-Assaad, “Should You Rust Proof Your New Car?” Auto-Guide.com, 21 March 2013). On political matters, especially when the disagreements are basi- cally over statistics, look to independent government agencies, such as the Census Bureau, or to university studies or other independent sources. Organizations like Doctors Without Borders are relatively impartial sources on the human rights situation in other countries because they practice medicine, not politics: they are not trying to support or oppose any specific government. Of course, independence and impartiality are not always easy to judge, either. Be sure that your sources are genuinely independent and not just interest groups masquerading under an independent- sounding name. Check who funds them; check their other publica- tions; look for their track record; watch the tone of their statements. Sources that make extreme or simplistic claims, or spend most of their time attacking and demeaning the other side, weaken their own claims. Again, seek out sources that offer constructive argu- ments and responsibly acknowledge and thoroughly engage the ar- guments and evidence on the other side. At the very least, try to confirm for yourself any factual claim quoted from a potentially bi- ased source. Good arguments cite their sources (Rule 13); look them up. Make sure the evidence is quoted correctly and not pulled out of context, and check for further information that might be helpful. 16 Cross-check sources Don’t bet on a one-off Consult and compare a variety of sources to see if other, equally good authorities agree. Are the experts sharply divided or in agreement? If they’re pretty much in agreement, theirs is the safe view to take—and the opposite view is, at the very least, unwise, how- ever strongly it may appeal to us. Authoritative views can certainly be wrong at times. But nonauthoritative views are regularly wrong.  16. Cross- check sources 29 On the other hand, cross-checking may sometimes reveal that the experts themselves disagree on some subject. In that case, reserve judgment yourself. Don’t jump in with two feet where truly informed people tread with care. Better to argue on some other grounds—or rethink your conclusions. What about our friend Aubrey de Grey, then, and our hopes of living 1,000 years? Alas, when you start to cross-check, it turns out that de Grey’s work is widely regarded as well-developed and his research as certainly worth pursuing, but very few other experts are persuaded.3 Many are sharply critical. He’s an outlier. Living vastly longer may be an appealing thought, but don’t count it very likely. On most significant topics you can probably find some disagree- ment if you look hard enough. Worse, on some topics the appearance of controversy may be created even when there is virtually no dis- agreement among qualified authorities. Although there was a time when experts disagreed about global climate change, for example, the world scientific community is now nearly unanimous that the cli- mate is changing and that human activity has something to do with it. Sure, there’s still loud disagreement in some media and election campaigns, but virtually none among trained climate scientists look- ing at the data as objectively as they can. There are also a few rea- soned critiques of the climate-change consensus, but in the best judg- ment of almost everyone actually in the field, they do not change the bottom line. Some of the critiques have even sharpened the science, but the critics, even when qualified, are (very markedly) outliers. Ideology seems to be the driving force here—not actual evidence or professional judgment. You may need to look into seeming contro- versies like these to see how seriously to take them.4 3. For de Grey’s popular presentation of his theories, see his book Ending Aging: The Rejuvenation Breakthroughs That Could Reverse Human Aging in our Lifetimes (St. Martins Griffin, 2008). A highly critical response by a group of fellow gerontologists is Huber Warner, et al., “Science Fact and the SENS Agenda,” EMBO Reports 2005 (6): 1006– 1008, http://embor.embopress.org/content/6/11/1006. 4. For a contemporary summary of the state of climate science, also addressing some skeptical claims, start with G. Thomas Farmer’s short textbook Modern Climate Change Science (Springer, 2015). Of course, once again, the consensus of experts may be wrong. Still, expert agreement is usually the best we can do. Even climate change “deniers” would not, say, go against the unanimous advice of their doctors if they were to learn that they might be seriously ill. They would not, so to say, bet their life that all their 30 17. Build your Internet savvy 17 Build your Internet savvy Online, even the most baseless or hateful opinion site can dress itself up to look plausible and even professional. Aca- demic book publishers and even most public libraries have at least some checks on the reliability and tone of the books and other ma- terials they collect, but on the Internet, it is still the Wild West—no checks. You’re on your own. “The Internet” by itself, in any case, is not any kind of authority. It merely transmits other sources. Savvy users know how to evalu- ate those sources—they apply the rules in this book. Rule 13, for example: What is the source? With many websites this may be dif- ficult to tell—and that’s a red flag right there. Are the sources well- informed (Rule 14)? Reliable (15)? Or are the sites pushing an agenda—trying to sell you something, or to manipulate your view on some issues by, say, using loaded language (5), unrepresentative data (8), or outlying or phony “experts” (14 and 16)? At minimum, cross-check other, independent websites on the same issue (16). Savvy users also dig deeper than the standard Web search. Search engines cannot search “everything”—far from it. In fact, the most reliable and detailed information on any given topic is often found in databases or other academic resources that standard search engines cannot enter at all. You may need a password; ask your teacher or librarian. Savvy users may also—cautiously!—consult Wikipedia. It’s cer- tainly true that “anyone can edit Wikipedia,” as is often objected, and as a result false and defamatory information has sometimes been posted. Subtle biases surely persist. Still, Wikipedia’s very openness doctors are wrong, no matter how fervently they might wish it. But they would have us bet the future of Earth itself that the consensus of climate experts is wrong? Current efforts on the part of some politicians to shut down climate research, and even to pre­ vent scientists from communicating with the public or public agencies from planning for climate-change adaptation, are even worse: they reveal not a constructive and evidence-based skepticism, but (it seems) just the opposite. Even responsible denial needs evidence!  17. Build your Internet savvy 31 can also be an advantage. Every article is subject to constant scrutiny and correction by other users. Many users are moved to contribute additional information or improvements too. Over time, many ar- ticles tend to become more comprehensive and neutral. Wikipedian editors sometimes intervene if there is too much contention, and some hot-topic articles are not open to general editing, but the end result is that Wikipedia’s error rate (remember Rule 9!) has been compared favorably even to the Encyclopedia Britannica.5 Of course, savvy encyclopedia users know that they cannot simply cite Wikipedia (or, usually, any other encyclopedia) to back up their claims. Wikipedia’s intention is to organize and summarize knowl- edge on a subject, and then to point readers to the real sources. Savvy users also remain watchful—as in any source—for subtle hints of loaded language, dismissive accounts of disfavored views, and the like. Every reference source is a product of a group of people with their limits and biases, acknowledged and unacknowledged. At least as important as avoiding mistakes or bias is having a means of correct- ing them—and fast—and at that Wikipedia is unexcelled. Random insertions and vandalism are typically repaired within minutes, and every change is tracked and explained (check out every page’s “View History” tab) and sometimes widely debated as well (check out the “Talk” tabs). What other reference source is so transparent and self- correcting? Really savvy users might join the work of making Wiki- pedia still better! 5. See Jim Giles, “Internet Encyclopedias Go Head to Head,” Nature 438 (7070): 900–1, December 2005. The March 2006 issue of Nature includes a response from Encyclopedia Britannica and a rejoinder from Nature.  V Arguments about Causes Did you know that students who sit at the front of the classroom tend to get better grades? And that people who are married are, on average, happier than people who aren’t? Wealth, by contrast, doesn’t seem to correlate with happiness at all—so maybe it is true after all that “the best things in life are free.” If you’d rather have the money anyway, you might be interested to know that people with “can-do” attitudes tend to be wealthier. So you’d better work on your attitude, eh? Here we come to arguments about causes and their effects—about what causes what. Such arguments are often vital. Good effects we want to increase, bad effects we want to prevent, and we often want to give appropriate credit or blame for both. It won’t surprise you, though, that reasoning about causes also takes care and critical thinking. 18 Causal arguments start with correlations The evidence for a claim about causes is usually a correlation—a regular association—between two events or kinds of events: between your grades in a class and where you sit in the class- room; between being married and being happy; between the unemploy­ ment rate and the crime rate, etc. The general form of the argument therefore is: Event or condition E1 is regularly associated with event or condition E2. Therefore, event or condition E1 causes event or condi- tion E2. 33 34 19. Correlations may have alternative explanations That is, because E1 is regularly associated with E2 in this way, we conclude that E1 causes E2. For example: People who meditate tend to be calmer. Therefore, meditation calms you down. Trends may also be correlated, as when we note that increasing vio- lence on television correlates with increasing violence in the real world. Shows on television portray more and more violence, callous- ness, and depravity—and society is becoming more and more violent, callous, and depraved. Therefore, television is ruining our morals. Inverse correlations (that is, where an increase in one factor cor- relates to a decrease in another) may suggest causality too. For example, some studies correlate increased vitamin use with decreased health, suggesting that vitamins may (sometimes) be harmful. In the same way, noncorrelation may imply lack of cause, as when we discover that happiness and wealth are not correlated and therefore conclude that money does not bring happiness. Exploring correlations is also a scientific research strategy. What causes lightning? Why do some people become insomniacs, or ge- niuses, or Republicans? And isn’t there some way (please?) to prevent colds? Researchers look for correlates to these conditions of interest: that is, for other conditions or events that are regularly associated with lightning or genius or colds, for example, but without which light- ning or genius or colds don’t tend to happen. These correlates may be subtle and complex, but finding them is often possible nonetheless— and then (hopefully) we have a handle on causes. 19 Correlations may have alternative explanations Arguments from correlation to cause are often com­pelling. However, there is also a systematic difficulty with any such claim. The problem is simply that any correlation may be  19. Correlations may have alternative explanations 35 explained in multiple ways. It’s often not clear from the correlation itself how best to interpret the underlying causes. First, some correlations may simply be coincidental. For example, though the Seattle Seahawks and the Denver Broncos both went to the Super Bowl in the same year that their home states legalized marijuana—2012—it’s not likely that these events were actually connected. Second, even when there really is a connection, correlation by itself does not establish the direction of the connection. If E1 is cor- related with E2, E1 may cause E2—but E2 may instead cause E1. For example, while it is true (on average) that people with “can-do” at- titudes tend to be wealthier, it’s not at all clear that the attitude leads to the wealth. It may be more plausible the other way around: that the wealth causes the attitude. You’re more apt to believe in the pos- sibility of success when you’ve already been successful. Wealth and attitude may correlate, then, but if you want to get wealthier, just working on your attitude may not get you very far. Likewise, it’s entirely possible that calmer people tend to be drawn to meditation, rather than becoming calmer because they meditate. And the very same correlation that suggests that television is “ruin- ing our morals” could instead suggest that our morals are ruining television (that is, that rising real-world violence is leading to an in- crease in the portrayal of violence on television). Third, some other cause may underlie and explain both of the correlates. Again E1 may be correlated with E2, but rather than E1 causing E2 or E2 causing E1, something else—some E3—may cause both E1 and E2. For example, the fact that students who sit in the front of the classroom tend to get better grades may not imply either that sitting in the front leads to better grades or that getting better grades leads to sitting in the front of the class. More likely, some students’ special commitment to making the most of their schooling leads both to sitting in the front of the classroom and to better grades. Finally, multiple or complex causes may be at work, and they may move in many directions at the same time. Violence on television, for example, surely reflects a more violent state of society, but also, to some degree, it surely helps to worsen that violence. Quite likely there are other underlying causes as well, such as the breakup of traditional value systems and the absence of constructive pastimes. 36 20. Work toward the most likely explanation 20 Work toward the most likely explanation Since a variety of explanations for a correlation are usually possible, the challenge for a good correlation-based argu- ment is to find the most likely explanation. First, fill in the connections. That is, spell out how each possible explanation could make sense. NO: Independent filmmakers generally make more creative films than the big studios. Thus, their independence leads to their creativity. There’s a correlation, yes, but the causal conclusion is a little abrupt. What’s the connection? YES: Independent filmmakers generally make more creative films than the big studios. It makes sense that with less studio control, independent filmmakers are freer to try new things for more varied audiences. Independents also usually have much less money at stake, and therefore can afford for a cre- ative experiment to fall flat. Thus, their independence leads to their creativity. Next, try to fill in the connections in this way not just for the explanation you favor, but also for alternative explanations. For ex- ample, consider studies that correlate increased vitamin use with ­decreased health. One possible explanation is that vitamins actually worsen health, or anyway that some vitamins (or taking a lot of them) are bad for some people. It is also possible, though, that people who already are in bad or worsening health may be using more vitamins to try to get better. In fact, this alternative explanation seems, at least at first glance, equally or even more plausible.  20. Work toward the most likely explanation 37 Finally, try to decide which is the most likely explanation for the correlation. You may need more information. In particular, is there other evidence that (some?) vitamins can sometimes be harmful? If so, how widespread might these harms be? If there is little direct and specific evidence of harm to be found, especially when vitamins are taken in appropriate dosages, then it’s more likely that poorer health leads to more vitamin use than that more vitamin use leads to poorer health. Or again: Marriage and happiness correlate (again, on average), but is it because marriage makes you happier or because happier people tend to be more successful at getting and staying married? Fill in the connections for both explanations and then step back to think. Marriage clearly offers companionship and support, which could explain how marriage might make you happier. Conversely, it may be that happy people are better at getting and staying married. To me, though, this second explanation seems less likely. Happiness may make you a more appealing partner, but then again it may not—it could instead make you more self-absorbed—and it is not clear that happiness by itself makes you any more committed or responsive a partner. I’d prefer the first explanation. Note that the most likely explanation is very seldom some sort of conspiracy or supernatural intervention. It is possible, of course, that the Bermuda Triangle really is spooked and that is why ships and planes disappear there. But that explanation is far less likely than another simple and natural explanation: that the Bermuda Triangle is one of the world’s heaviest-traveled shipping and sailing areas, with tropical weather that is unpredictable and sometimes severe. Besides, people do tend to embellish spooky stories, so some of the more lurid accounts, having passed through countless retellings, aren’t (let’s just say) the most reliable. Likewise, although people fasten onto inconsistencies and oddi- ties in dramatic events (the JFK assassination, 9/11, etc.) to justify conspiracy theories, such explanations usually leave a great deal more unexplained than the usual explanations, however incomplete. (For instance, why would any plausible conspiracy take this particular form?) Don’t assume that every little oddity must have some nefari- ous explanation. It’s hard enough to get the basics right. Neither you nor anyone else needs to have an answer for everything. 38 21. E xpect complexity 21 Expect complexity Plenty of happy people are not married, of course, and plenty of married people are unhappy. Still, it does not follow that marriage has no effect on happiness on average. It’s just that happiness and unhappiness (and, for that matter, being married or unmarried) have many other causes too. One correlation is not the whole story. The question in such cases is about the relative weight of different causes. If you or someone else has argued that some E1 causes some E2 , it is not necessarily a counterexample if occasionally E1 doesn’t pro- duce E2, or if another cause entirely may also sometimes produce E2. The claim is just that E1 often or usually produces E2, and that other causes less commonly do, or that E1 is among the major contributors to E2, though the full story may involve multiple causes and there may be other major contributors too. There are people who never smoke cigarettes at all and still get lung cancer, and also people who smoke three packs of cigarettes a day and never get it. Both effects are medically intriguing and important, but the fact remains that smoking is the prime cause of lung cancer. Many different causes may contribute to an overall effect. Though the causes of global climate change are many and varied, for instance, the fact that some of them are natural, such as changes in the sun’s brightness, does not show that human contributions therefore have no effect. Once again, the causal story is complex. Many factors are at work. (Indeed, if the sun is also contributing to global warming, there’s even more reason to try to decrease our contribution.) Causes and effects may “loop,” too. Filmmakers’ independence may lead to their creativity, but, then again, creative filmmakers may seek independence from the start, leading to more creativity, and so on. Others may seek both creativity and independence because they prefer a less pressured life, or maybe they just have some great idea that they can’t sell to a big studio. It’s complicated....  VI Deductive Arguments Consider this argument: If there are no chance factors in chess, then chess is a game of pure skill. There are no chance factors in chess. Therefore, chess is a game of pure skill. Suppose that the premises of this argument are true. In other words, suppose it’s true that if there are no chance factors in chess, then chess is a game of pure skill—and suppose there are no chance factors in chess. You can therefore conclude with perfect assurance that chess is a game of pure skill. There is no way to admit the truth of these premises but deny the conclusion. Arguments of this type are called deductive arguments. That is, a properly formed deductive argument is an argument of such a form that if its premises are true, the conclusion must be true too. Properly formed deductive arguments are called valid arguments. Deductive arguments differ from the sorts of arguments so far considered, in which even a large number of true premises does not guarantee the truth of the conclusion (although sometimes they may make it very likely). In nondeductive arguments, the conclusion un- avoidably goes beyond the premises—that’s the very point of arguing by example, authority, and so on—whereas the conclusion of a valid deductive argument only makes explicit what is already contained in the premises, though it may not be clear until it is spelled out. In real life, of course, we can’t always be sure of our premises ­either, so the conclusions of real-life deductive arguments still have to be taken with a few (sometimes many) grains of salt. Still, when strong premises can be found, deductive forms are very useful. And 39 40 22. Modus ponens even when the premises are uncertain, deductive forms offer an effec­ tive way to organize arguments. 22 Modus ponens Using the letters p and q to stand for declarative sentences, the simplest valid deductive form is If [sentence p] then [sentence q]. [Sentence p]. Therefore, [sentence q]. Or, more briefly: If p then q. p. Therefore, q. This form is called modus ponens (“the mode of putting”: put p, get q). Taking p to stand for “There are no chance factors in chess,” and q to stand for “Chess is a game of pure skill,” our introductory example follows modus ponens (check it out). Here is another: If drivers on cell phones have more accidents, then drivers should be prohibited from using them. Drivers on cell phones do have more accidents. Therefore, drivers should be prohibited from using cell phones. To develop this argument, you must explain and defend both of its premises, and they require quite different arguments (go back and look). Modus ponens gives you a way to lay them out clearly and sepa- rately from the start.  23. Modus tollens 41 23 Modus tollens A second valid deductive form is modus tollens (“the mode of taking”: take q, take p). If p then q. Not-q. Therefore, not-p. Here “Not-q” simply stands for the denial of q, that is, for the sen- tence “It is not true that q.” The same is true for “not-p.” Want to play detective? Sherlock Holmes used a modus tollens ­argument at a key moment in “The Adventure of Silver Blaze.” A horse had been stolen out of a well-guarded barn. The barn had a dog, but the dog did not bark. Now what do we make of that? A dog was kept in the stables, and yet, though someone had been in and had fetched out a horse, [the dog] had not barked.... Obviously the... visitor was someone whom the dog knew well.6 Holmes’s argument can be put as a modus tollens: If the visitor were a stranger, then the dog would have barked. The dog did not bark. Therefore, the visitor was not a stranger. To write his deduction in symbols, you could use s for “The visitor was a stranger” and b for “The dog barked.” If s then b. Not-b. Therefore, not-s. 6. Sir Arthur Conan Doyle, “The Adventure of Silver Blaze,” in The Complete Sherlock Holmes (Garden City, NY: Garden City Books, 1930), p. 199. 42 24. Hypothetical syllogism “Not-b” stands for “The dog did not bark,” and “not-s” stands for “The visitor was not a stranger.” As Holmes puts it, the visitor was someone whom the dog knew well. It was an inside job! 24 syllogism.” If p then q. Hypothetical syllogism A third valid deductive form is “hypothetical If q then r. Therefore, if p then r. For instance, remember this argument from Rule 6: When you learn to care for a pet, you learn to attend to the needs of a dependent creature. When you learn to attend to the needs of a dependent creature, you learn to be a better parent. Therefore, when you learn to care for a pet, you learn to be a better parent. Separating out and slightly rephrasing the premises into “if-then” form: If you learn to care for a pet, then you learn to attend to the needs of a dependent creature. If you learn to attend to the needs of a dependent creature, then you learn to be a better parent. Therefore, if you learn to care for a pet, then you learn to be a better parent. Using the letters in boldface to stand for the component sentences in these premises, we have:  25. Disjunctive syllogism 43 If c then a. If a then p. Therefore, if c then p. And you see why using consistent terms and phrasing helps so much! Hypothetical syllogisms are valid for any number of premises, as long as each premise has the form “If p then q” and the q (called the “consequent”) of one premise becomes the p (the “antecedent”) of the next. 25 syllogism.” p or q. Disjunctive syllogism A fourth valid deductive form is “disjunctive Not-p. Therefore, q. For example, suppose we continue playing detective: Either Dorabella or Fiordiligi stole the tarts. But Dorabella didn’t do it. The implication is pretty clear... Using d for “Dorabella stole the tarts” and f for “Fiordiligi stole the tarts,” we have Either d or f. Not d. Therefore, f. There is one complication. In English the word “or” can have two different meanings. Usually “p or q” means that at least one of p or q is true, and possibly both. This is called an “inclusive” sense of the 44 26. Dilemma word “or” and is the sense normally assumed in logic. Sometimes, though, we use “or” in an “exclusive” sense, in which “p or q” means that either p or q is true but not both. “Either they’ll come by land or they’ll come by sea,” for example, suggests that they won’t come both ways at once. In that case you might be able to infer that if they come one way, then they’re not coming the other way (better be sure!). Disjunctive syllogisms are valid regardless of which sense of “or” is used (check it out). But what else, if anything, you may be able to infer from a statement like “p or q”—in particular, whether you can conclude not-q if you also know p—depends on the meaning of “or” in the specific “p or q” premise you are considering. (For exam- ple, if we knew only that Dorabella stole the tarts, can we be sure Fiordiligi didn’t help?) Take care! 26 p or q. If p then r. Dilemma A fifth valid deductive form is the “dilemma.” If q then s. Therefore, r or s. Rhetorically, a dilemma is a choice between two options both of which have unappealing consequences. The pessimist philosopher Arthur Schopenhauer, for example, formulated what is sometimes called the “Hedgehog’s dilemma,” which we could paraphrase like this: The closer two hedgehogs get, the more likely they are to poke each other with their spikes; but if they remain apart, they will be lonely. So it is with people: being close to some- one inevitably creates conflicts and provocations and opens us to a lot of pain; but on the other hand, we’re lonely when we stand apart.  27. Reductio ad absurdum 45 In outline this argument might be put: Either we become close to others or we stand apart. If we become close to others, we suffer conflict and pain. If we stand apart, we’ll be lonely. Therefore, either we suffer conflict and pain or we’ll be lonely. And in symbols: Either c or a. If c then s. If a then l. Therefore, either s or l. A further argument in dilemma form could conclude, even more simply, something like “Either way we’ll be unhappy.” I’ll leave this one to you to write out formally. Since this is such a jolly little conclusion, maybe I should add that hedgehogs are actually quite able to get close without poking each other. They can be together and comfortable too. So Schopenhauer’s second premise turns out to be false—at least for hedgehogs. 27 Reductio ad absurdum One traditional deductive strategy deserves spe- cial mention even though, strictly speaking, it is only a version of modus tollens. This is the reductio ad absurdum, that is, a “reduction to absurdity.” Arguments by reductio (or “indirect proof,” as they’re sometimes called) establish their conclusions by showing that as- suming the opposite leads to absurdity: to a contradictory or silly result. Nothing is left to do, the argument suggests, but to accept the conclusion. 46 27. Reductio ad absurdum To prove: p. Assume the opposite: Not-p. Argue that from the assumption we’d have to conclude: q. Show that q is false (contradictory, “absurd,” morally or practically unacceptable... ). Conclude: p must be true after all. Consider this intriguing little argument, for example: No one has yet had sex in space.