Critical thinking
“I don’t get why you want to quit,” said Malcolm. “You came here to play volleyball. Volleyball is all you ever want to talk about! Now suddenly you want to quit?”

Caitlin looked at Malcolm. He couldn’t possibly be this dense. “Look, I explained it all to you already.”

“You said that you didn’t like Coach Williams. So what? She’s your head coach. Nobody likes a head coach. I don’t like the marching band director, but you don’t see me quitting the band,” said Malcolm.

“Coach was screaming at everyone again. She’s so negative, always screaming at the players, and that doesn’t motivate me to try harder. I just hate all her yelling! Anyway, it’s the setter, Jenny; she kept putting the ball too far from the net. It messes up everybody. But coach kept yelling at the rest of us, when it was all Jenny’s fault.”

“So,” said Malcolm, “you’re quitting because the coach yells at you? Williams has been a screamer since she took over as head coach two seasons ago. Her yelling never bothered you before. Or is it something else?”

“Yes! No. I don’t know,” replied Caitlin in exaspera- tion. “Who cares? It’s not like I have a future in volleyball after college.”

“What does that have to do with anything? You knew a spot on the Olympic team or the AVP beach volleyball pro tour was like a near-impossible long shot before you came here. And another thing: Don’t tell me you don’t get moti- vated when the coach is fired up. I’ve seen you in games. You’re angry because you know you can play Jenny’s posi- tion better than she can. But the coach doesn’t let you. So, you’re pissed at the coach. It’s not about the yelling.”

“You’re right. Jenny’s terrible. I don’t understand how she ever made the team.”

“But, Caitlin, nobody can spike and defend at the net like you. Coach knows that, and so does everyone else on the team. So, you’re going to play the front line. Which is great. I’ll bet that Jenny wishes she could play where you play.”

“Well, I don’t care about any of that anymore. I’m quitting and therefore I’m quitting. End of story. Let’s talk about something else. . . . Tell me how your marching band practice was today.”

“Fine, I hear you. You’re going to quit. And, yes, we can change the subject. But let me just say for the record that I still don’t think you’re really being honest about why you’re leaving the team and the sport you love. And just saying over and over again that you plan to quit does not explain why you plan to quit.”

In the scene that just played out, Caitlin explains her decision to quit the college volleyball team. Her stated reason is that she is not motivated to play harder by the coach’s constant criticism. Ergo, she’s going to quit the team. That may be a reasonably logical argument, if we also assume that Caitlin is the kind of athlete who does

not respond well to that coaching style. But her friend Malcolm knows better. He does not accept her argument because he has seen her respond positively to the coach’s style in game situations. The truth is that Caitlin does get motivated to play harder when the coach is fired up. Although Malcolm does not make the point, we might observe that the word yelling is negatively slanted. It fits Caitlin’s current negative attitude toward the coach. But “yelling” is probably not the best word to use when talk- ing about those times when the coach is successful in motivating Caitlin.

Caitlin offers another argument, saying that she has no future in volleyball. Malcolm points out the irrelevance of that consideration, and then he suggests that her real rea- son for being upset with her coach has to do with which position she wants to play. Caitlin ends the conversation about volleyball with a definitive and somewhat defensive, “I’m quitting and so I’m quitting.” Malcolm makes it clear that her final statement forcefully affirms her intention, but it is not an acceptable answer to the question “Why?”

Throughout their conversation Malcolm has been evaluating his friend Caitlin’s arguments. This chapter focuses on building argument evaluation skills. It presents a comprehensive and straightforward evaluative process that we can apply in everyday situations, much in the way that Malcolm did in the opening conversation with Caitlin. The process includes four specific tests. An argument must pass all four tests to be considered worthy of acceptance as proof that its conclusion is true or very probably true. Each of these four criteria is rooted in the natural and universal human practice of making arguments and giving reasons. Because critical thinking requires skill at evaluating argu- ments in real-life contexts, we begin with the expectations and responsibilities associated with giving reasons and making arguments.

7.1 Giving Reasons and Making Arguments

The dynamic conversational practice of explaining to one another the reasons for our claims—that is of making arguments—is part of every human civilization and cul- ture. Every natural human language includes terminol- ogy and social conventions for making arguments as well as for evaluating them. But argument making is sensible only because of a set of presumptions we all implicitly rely upon to engage in this practice successfully. These presumptions are operative wherever and whenever peo- ple engage in a sincere effort to make arguments to one another regarding a decision about something of serious mutual concern. These presumptions form the basis for the expectations the listener has—and the responsibilities

the argument maker has—when offering reasons to explain why the argument’s claim is worthy of acceptance as true or very probably true.

Truthfulness

The practice of argument making rests in part on the presumption upon which so much of human discourse depends, namely that the speaker is telling the truth. In other words, when making arguments we expect that the statements offered as part of any reason are, in fact, true. As a rule, people collaborating with one another to think something through do not intentionally use erroneous information or lie to one another. If a disagreement about the truth of any statement that is part of a reason should arise, then the people involved have two options. They can make an effort to find out if that statement is true, or they can qualify the force with which they assert and maintain any claims in the line of reasoning that relies on that state- ment. Of course, people do lie on occasion. And so this presumption often goes unfulfilled.

In Chapter 5 we used the familiar term premise to refer to a statement, either explicit or implicit, that is a compo- nent of a reason. Another way to express the truthfulness presumption is like this: In a conversation that involves making arguments, we expect that all the premises offered are in fact true.1

The assumption that premises are true provides a reasonable basis for moving to consider whether those premises imply that the conclusion is true or very prob- ably true. But without first really considering the truth- fulness of the premises, it becomes only a conceptual exercise, rather than a matter of practical significance, to consider the argument’s logical strength. Here are two arguments with true premises.

• Chicago is north of St. Louis. St. Louis is north of New Orleans. Therefore, Chicago is north of New Orleans.

• There are 325 children registered in grades 1 through 6 at the Carver Elementary School. We have tested 40 percent of these children for reading skills. We also have taken a number of physiological measurements of each of those same children. Our data show that there is a strong positive statistical correlation be- tween the size of a child’s feet and the child’s reading skill level.

Not sure if the premises in the first example are true? No problem. We can check a map or pull up Google Earth and find the relative position of the three cities mentioned. Regarding the second example, one obvious question is whether the measurements mentioned in the third sentence included foot size. If not, we may want to call into question the truthfulness of what the speaker is saying. If the speaker does not have any information about the children’s foot sizes, then the speaker’s argu- ment falls apart.

Logical Strength

Consider the following example. In this case, were we to take the premises to be true, then its conclusion would have to be taken as true as well.

• We have been keeping track of how often the weekday 6:56 am Caltrain from San Francisco arrives late at the Millbrae station. We conducted three 6-week surveys over the past 12 months. In each survey the week- day train arrived at the Millbrae station late 24 out of 30 times. Therefore, there is an 80 percent probability that the weekday 6:56 am Caltrain will arrive late at the Millbrae station.

In this next example let’s assume that what the speaker is saying about John is true and let’s assume that we agree with the speaker about the pattern of behavior that is the precursor to a breakup. If so, then it seems reasonable to conclude that the relationship with John will not endure. • This is not the first time someone has broken up with me. I recognize the pattern. First the person is too busy to do things together. Then the person doesn’t return texts or phone calls. Then the person “forgets” that we had plans. And then comes the “we can still be friends” conversation. John has progressed to the “too busy” phase. As much as I don’t want to believe it, my rela- tionship with John is probably heading for a break up.

Assume, for this next example, that there was a comet one night and that the next day the king took ill. So the premises are true. But the reasoning is an unacceptable leap from those observations to a claimed causal relation- ship. The premises of this argument do not logically justify accepting conclusion as true.

• I saw a strange light streak across the midnight sky last night. And, look, this morning the king became deathly ill. This can only mean that the strange light in the night sky caused our king’s sickness.

When someone offers an argument, the speaker’s reason is supposed to be the logical basis for the speak- er’s claim. The point of giving reasons for our claims is that the reasons support the claims. The second

presupposition of the practice of argument making is that the speaker’s reason, if true, is the logical basis for the speaker’s claim. Notice that this is hypotheti- cal. Were we to assume that the reason a person gives for his or her claim is true, that assumption would then imply that the person’s claim is probably or necessarily true as well. In the language of logic, this presupposition is expressed this way: The assumed truth of the premises of an argument justifies or implies that the conclusion of the argument also be taken as true.

Most people would sooner die than think; in fact, they do so.

Bertrand Russell, Author, Mathematician, & Philosopher2

Relevance

It happens that a conclusion might be true independent of whether the premises are true or whether the premises logically support the conclusion; because this is so, when we make arguments we also presume that the truth of the reason is relevant to the claim. This presumption might be called the “So What?” presumption. Consider this

example, where the premises are true and the conclusion is true, but the reason is not relevant to the claim.

• To many around the world, the Statue of Liberty sym- bolizes the welcome our nation extends to all freedom- loving people. So, as the great Yogi Berra says, “You can observe a lot just by watching.”

This argument is so odd that it would get a squawk out of the Aflac duck. The reason given has no relevance to the truth of the claim. Their only connection is that Yogi Berra happened to have been a player for the New York Yankees, and the Statue of Liberty happens to be in New York. That happenstance is not sufficient to say that the one is relevant to the other. If anyone were to seriously present this rea- son as the basis for the truth of the conclusion we would say, “So what? That’s not relevant!” And this reveals our third presupposition: the listener takes the reason given by the speaker to be relevant in believing the speaker’s claim.

There is no point to giving reasons if the listener is not going to rely on those reasons in deciding what to believe with regard to the claim. Recall that in our opening example, Caitlin changed her story about why she wanted to quit the volleyball team. At first she talked about how the coach’s yelling and berating players was her issue. But then she gave a different reason, saying that she was going to quit because she did not anticipate a future as a professional volleyball player. Malcolm challenged her on that, noting that it was not even relevant, in his view. A future in professional volleyball was never her reason for joining the college team, and the absence of that opportu- nity is not relevant to why Caitlin now wants to quit the team. Everyone, including Caitlin, may believe that Caitlin wants to quit the volleyball team. But nobody, not even Caitlin, believes that whether or not she has a future in professional volleyball has anything to do with her want- ing to quit at this point in time.

Non-Circularity

Our fourth precondition when we give reasons for our claims is that the claim must not be part of the basis for believ- ing in the truth of the reason. Argument making in real life is essentially a one-way street: The reasons are used to

because in mapping arguments we used the arrow con- vention to display the intended directionality of the argu- ment maker’s reasoning.

In the Dilbert’s cartoon strip the boss criticizes Dilbert’s presentation for being full of technical words and way too long. We naturally think that the boss came to those conclusions about the presentation by having seen it and evaluated it. But no. The boss then turns around and uses those same two claims as his reasons for not seeing or evaluating the presentation. It makes no sense to give a reason as the basis for one’s claim and then to use that claim as the basis for one’s reason. In a comic strip, circular reasoning is funny, and in real life it can be infuriating.

7.2 The Four Tests for Evaluating Arguments

The four presumptions about argument making as an interpersonal human activity form the bases for the four evaluative criteria applicable to all arguments. In other words, it would be reasonable to accept a person’s argu- ment if it met all four of the conditions implied by those presumptions. Given a reason offered in support of a claim, these are the four conditions that must be met:

1. To the best of our knowledge and understanding, the reason is true.

2. The logical relationship between the reason and claim is such that the reason implies, entails, strongly warrants or strongly supports the claim, such that the claim must be true or very probably true if the reason is as- sumed to be true.

3. The relevance of the reason to the claim is such that the truth of the claim actually depends on the truth of the reason.

4. The flow of the reasoning is such that truth of reason must not depend on the truth of the claim.

An argument that satisfies all four conditions is wor- thy of our acceptance as a proof that its claim is true or very probably true. We will apply the adjectives good and

worthy to those arguments. A good argument or a worthy argument is an argument that merits being accepted as a proof that its conclusion is true or very probably true. The four conditions listed to define four tests to apply when evaluating arguments are to be applied in the order given. As soon as an argument fails to meet one of the four, it is no longer eligible to be considered a good or worthy argument. Let’s see how to apply each of these four to determine whether or not an argument is worthy of acceptance.

Test #1: Truthfulness of the Premises

In everyday situations, the truth or falsity of premises is our first concern. If one or more of the premises of an argu- ment is not true, then, for all practical purposes, there is little point in moving forward to evaluate other aspects of the argument. Our first job is to get our information straight. The critical thinking habits of truth-seeking and inquisitiveness demand that we cou-

rageously endeavor to learn what we can before mov- ing forward with claims and arguments based on incomplete knowledge.

The Test of the Truth- fulness of the Premises is a favorite in police dra- mas. We have all seen the scene in which detectives interrogate someone who gives a lame alibi like this one: “My friends and I were at a movie the night the crime took place.” The detectives check the story and discover it is a lie. Having

A person who has never been drunk cannot be an alcoholic.

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exposed his lack of truthfulness, the detectives no longer accept the person’s alibi and may even make the liar their prime suspect.

Test #2: Logical Strength

One practical way to apply the Test for Logical Strength is to challenge yourself to imagine a situation, if possible, in which all the premises of an argument are true, but the con- clusion is false. If there is no possible scenario in which all the premises of an argument can be true while at the same time its conclusion is false, or if such a scenario is extremely improbable, then the argument passes the Test of Logical Strength.3 However, to the extent that such a scenario is possible, plausible, likely, or actually true, the argument fails this test.4 If there is a possible scenario, but it is remote and implausible, perhaps as unlikely as 1 chance in 20 or 1 chance in a 1,000, then we can maintain a comparable degree of confidence in the argument’s logical strength. Logicians call an argument with true premises that has also passed the Test of Logical Strength a sound argument.5 Sound is used here in the sense of “healthy,” meaning that such an argument ordinarily is rather robust and deserves our attention as we deliberate what to do or what to believe.

What if there is more than one independent reason given to support a claim? Does discovering that one reason has a false premise make the claim unacceptable? Consider this example; here a claim is supported by two reasons, which the speaker wants the listener to take as indepen- dent considerations.

• “I’m not an alcoholic. First of all, I only drink beer. And, second, I’ve never been drunk in my life.”

Map #1 shows the two reasons as independently sup- porting the claim.

Suppose we discover that the speaker is telling the truth when he says that he only drinks beer. However, the implicit but unspoken premise (“Someone who only drinks beer

cannot be an alcoholic”) is false. So, the first argument fails the Test of the Truthfulness of the Premises. Suppose we then discover that the speaker is also being truthful when he says that he has never been drunk in his life. This, along with the generally accepted truth of the implicit, but unspoken, prem- ise “A person who has never been drunk cannot be an alco- holic,” indicates that his second argument passes the Test of Truthfulness of the Premises.

The Test of Logical Strength comes next, and the sec- ond argument also passes that test. It is difficult to imag- ine a case where a person who has never been drunk is an alcoholic, although it is not impossible to imagine such a case. So, it would seem reasonable to accept that our speaker is not an alcoholic, even though one of his reasons (that he only drinks beer) was poor. His second argument, based on the other reason (he has never been drunk in his life), which is independent of the first, was sound.

People often provide multiple independent reasons for a given claim and some of those reasons may turn out to be false. One may be inclined to dismiss the claim itself, having heard the speaker present one unsound argument.

Dismissing an otherwise-worthy claim simply because one or more of the arguments made on its behalf contains false reasons is one of the most common human reasoning errors. Before determining that a claim should be rejected, a strong critical thinker would first need to find problems with the soundness of all the arguments being advanced.

Because there are so many important varieties of argu- ments, which require special attention when testing for logi- cal strength, we will suspend this discussion at this point but return to it again in the coming chapters. We will devote Chapters 8 and 9 to the evaluation of inferences. And then later we will look more closely at inferences based on pat- tern recognition, ideological reasoning, and empirical rea- soning. For the moment, let’s complete our review of the four basic tests of an argument’s worthiness to be accepted.

Test #3: Relevance

The Test of Relevance requires making a reasoned judg- ment that the truth of the conclusion depends upon the truth of the reason given. If an argument passes the first twotests, then The Test of Relevance is the next one to apply. Recall that the presumption we are seeking to fulfill is that the author’s reason is, in fact, the basis for believing the claim. And the listener must judge if accepting the claim as true depends on support derived from that reason. For example, the following example passes the Test of Relevance.

• A study from the Harvard Center of Risk Analysis estimates that cell phone use while driving contributes to 6 percent of crashes, which equates to 636,000 crashes, 330,000 injuries, 12,000 serious injuries, and 2,600 deaths each year. The study also put the annual financial toll of cell phone– related crashes at $43 billion. The research investigated whether or not a hands-free device was less dangerous. The statistical evidence suggests not. It appears from the data that the fact that the driver was distracted by the conversation was a greater factor than was the type of cell phone technology, hands-free or not, that was being used. The researchers concluded that using cell phone technol- ogy of any kind while driving was associated with a greater risk of automobile accidents.6

By contrast, the next argument fails the Test of Relevance.

Is it reasonable or ethical for another driver to expose you to greater risk just so he or she can text a friend?

Evaluate Arguments: Four Basic Tests 145

So, how does a person connect San Francisco’s Golden Gate Park with a trip to the Botoli Garden in Florence, Italy? Find out about the influence that unreflective associational thinking has on human decision making in Chapter 10.

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• Yeah, I’m looking forward to visiting Italy, you know, Old Europe. Why is too obvious. See, I’ve been work- ing part-time at the Golden Gate Park in San Francisco. It’s incredible there. Beautiful, open, free. There’s this one garden there that kind of reminds me of pictures I’ve seen of Italy. I love being outside in the spring, the flowers and the fresh air, the smell of fresh-cut grass. And all that makes me think how great it would be to just live slow and relaxed, like they do in Europe, tak- ing life as it comes. You know what I mean?

That the research on car accidents and cell phone usage is relevant to the conclusion in the first example is obvious in the first example. The connection between visit- ing Italy and working part-time in Golden Gate Park in the second example seems to be tenuous at best, more based on the person’s free association of ideas than on any actual evidence. Even if the speaker imagines a connection, the listener can judge that the reason given, even if true, is not a basis for believing that the speaker wants to visit Italy. In fact, if the speaker had simply said, “I want to visit Italy,” that might have been more credible than his having come up with the far-fetched and irrelevant dissertation about the glories of a part-time job in a city park—even if it is one of the greatest public parks in this nation.

Applying the Test of Relevance is substantially easier for people with knowledge and experience appropriate to the context and issues under discussion. For example, U.S. laws prohibiting using gender as the basis for workplace promotions express American society’s judgment that a per- son’s gender is not a relevant consideration when deciding whether the person merits a promotion. In another country with a different set of cultural mores, gender-based promo- tion decisions might be considered both legal and reason- able. The Test of Relevance is important because people often make the argument that they should be excused from

responsibility for certain actions. However, as a people, having heard these arguments before, we have come to the judgment that certain reasons are not going to be accepted as relevant. For example:

• Claiming that one was following the direct orders of one’s superior is not a relevant defense against charges of war crimes.

• Claiming that one’s judgment was impaired by drugs or alcohol is not a relevant defense against charges of vehicular manslaughter resulting from driving while under the influence.

• Claiming that one must protect his or her GPA because one plans to become a doctor is not a relevant defense against charges of academic dishonesty in any course, including general education elective courses.

Test #4: Non-Circularity

The fourth and final test of an argument’s acceptability is the Test of Non-Circularity. This test requires that a claim is not being relied upon either implicitly or explicitly as part of a chain of reasoning used to support its own rea- son. If such a chain looping back on itself is found, then the argument maker is reasoning in a circle. An argument is like a river that flows in one direction, from reasons and

evidence toward the conclusion. A river cannot feed itself and still be described as a river; rather, it becomes a stag- nant moat. So it is with good arguments: Claims cannot be the bases for their own reasons. If they were, then the rea- soning would simply be stagnant and self-justifying in the most unflattering sense.

The final argument Caitlin made about quitting the volleyball team was “I’m quitting and therefore I’m quit- ting.” Here the circle is so tight that the reason and the

claim are identical. The map of her circular argument would look something like Map 2.

We can interpret this way of speaking as a way of emphasizing one’s claim, but not as a way of proving one’s claim. It is like saying “I’m quitting” real loud. But volume is not proof.

Reasoning in a circle results most frequently from the use of multiple arguments in combination with each other. At times people lose track of the reasons for their beliefs, forgetting, for example, that their basis for believ- ing one idea, X, was because they accepted another idea, Y, and that their reason for accepting Y had been their belief in X. The result is that the person has high con- fidence, although misplaced, in both ideas. However, because their support for X is Y and their support for Y is X, the reasonable thing would be to have no confidence in either. For example, consider the pair of arguments in this passage:

• I’m sure we can make this marriage work. That’s why we’re talking through our problems, which shows that we still care for each other. And that’s why I’m sure we can make this marriage work.

The speaker’s reason for the claim that the marriage is salvageable is the belief that both parties still care for each other. And the basis for believing that goes back to the idea that the marriage can be saved. If we were to map

these arguments, it would look like Map 3. This reasoning is as fragile as a house of cards; touch it in the least with an analytical finger and it collapses upon itself.

Argument Making Contexts

There is nothing about argument making that demands that the format be a debate. There is nothing about argument making that requires that it be an adver- sarial confrontation either. In fact, it does a great dis- service to decision making and collaborative effort to imagine the process must be oppositional or confronta- tional. In an adversarial context, it is too easy to forgo truth-seeking in the false belief that argument making is simply the search for facts that support one’s preconcep- tions. Too often, the courageous desire for best knowl- edge is trumped by the competitive need to vanquish the opposition. In that case, the honest pursuit of reasons and evidence, wherever they may lead, even if the rea- sons and evidence go against one’s preconceptions or interests, is abandoned because intellectual honesty and integrity are not always suitable virtues for warriors …

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