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Chapter 9. Evaluating Analogical Arguments

Think back to the discussion about whether to support the Smoke-Free Campus Initiative in Chapter 1. Among the responses presented was the following:

Using the skills you learned in Chapter 5, you should recognize this passage as containing an analogical argument. An analogical argument, you may recall, is an inductive argument that uses an analogy to conclude that, because one case has some feature, the other case should, too. In this example, James is comparing banning smoking on campus to banning alcohol and drug use on campus. When he asks his final question and answers it with “Wrong!” he implies that banning alcohol and drugs on campus has not stopped alcohol and drug consumption. From this, he concludes that banning smoking on campus will not stop smoking. In this chapter, you will discover that all analogical arguments, including this one, have the same basic structure and will practice identifying the core elements of that structure—namely, the source, target, and feature in the argument. You will then use that information to evaluate the strength of analogical arguments.

Learning Outcomes

In this chapter, you will learn how to evaluate analogical arguments by:

· Identifying the source, target, and feature in an analogical argument;

· Determining how many analogies are presented in the argument;

· Determining how many similarities are presented in the subargument;

· Determining how relevant the similarities are to the feature; and

· Writing a Critical Précis of an analogical argument.

Analyzing Analogical Arguments

Every analogical argument has the same basic structure. We will refer to this structure as the general form of analogical arguments. In its general form, each analogical argument contains two premises supporting the conclusion. One premise provides the analogy, and the other premise identifies the feature that the arguer concludes must be shared by the analogues. This general form for analogical arguments can be stated as follows:

P1:	The target is like the source.
P2:	The source has a particular feature.
∴	The target has the feature .

The first premise above presents the analogy. An analogy is a comparison of two (or more) things, typically called analogues. One of the analogues is called the source, and the other is called the target. The source (S) is the analogue that is given only among the premises. The target (T) is the analogue that the arguer is drawing a conclusion about; it will be found in both the analogy and the conclusion. The feature (F) is the characteristic of the source that the arguer is trying to prove is also a characteristic of the target.

Although some analogical arguments may be constructed differently, they can all be translated into this general form. Here’s an example of an analogical argument, followed by a Formal Analysis of the argument highlighting the source, target, and feature.

Buying an energy-efficient washing machine should save you money in the long run. This is because energy-efficient washing machines are like energy-efficient dishwashers, and energy-efficient dishwashers save buyers money in the long run.

P1:	Energy-efficient washing machines are like energy-efficient dishwashers.
P2:	Energy-efficient dishwashers save buyers money in the long run.
∴	Energy-efficient washing machines save buyers money in the long run.
Issue:	Whether energy-efficient washing machines save buyers money in the long r

Accurately identifying the source, target, and feature is critical for the evaluation of analogical arguments. Here is an example of the proper identification from the previous argument.

· Source: energy-efficient dishwashers

· Target: energy-efficient washing machines

· Feature: save buyers money in the long run

Some analogical arguments present the analogy with the source and target in a different order, as in this example.

Since my old laptop lasted over three years, it’s reasonable to conclude that this new laptop will last over three years, too. This is likely because my old laptop is like my new laptop.

Exercise 9.1.

· Your Turn! Write a Formal Analysis of the argument presented above. Then label the source, target, and feature.

Don’t let the order of the analogues fool you into misidentifying them. The source will be found only in the premises of the argument, and the target will be found in both the analogy and the conclusion. Thus, the proper identification of the parts is:

· Source: my old laptop

· Target: my new laptop

· Feature: will last over three years

Exercise 9.2.

For each analogical argument, complete a Formal Analysis, and then state the source, target, and feature.

1. The new model of Avenger running shoes is like the past model of Avenger running shoes. The past model has a great deal of cushioning in the sole. Therefore, the new model probably has a great deal of cushioning in the sole.

2. Masking tape is similar to duct tape. Masking tape can be used on paper, so duct tape can probably be used on paper.

3. Beefsteak tomatoes are very juicy. Roma tomatoes are like Beefsteak tomatoes. Thus, Roma tomatoes are likely to be juicy.

4. The Spanish explorer Fernando Cortez was much like the English explorer Sir Francis Drake. Given that Cortez was eager to increase his country’s influence in the New World, it seems probable that Drake was also eager to increase his country’s influence in the New World.

5. A screwball is probably a very hard pitch to hit. This is because a screwball is like a curve ball, and a curve ball is a very hard pitch to hit.

6. The second chemistry exam is similar to the first chemistry exam. Because you did well on the first exam, it’s likely that you will do well on the second exam.

7. Driving while under the influence of marijuana is a lot like driving under the influence of alcohol. Since you will lose your license if you are caught driving while under the influence of alcohol, you are also likely to lose your license if you are caught driving while under the influence of marijuana.

8. A Canadian porcupine is akin to an African porcupine. Therefore, a Canadian porcupine probably does not “throw” its quills because an African porcupine does not “throw” its quills.

9. The reason that the Hudson River is probably less polluted than it was a couple of decades ago is that the Hudson River is like the James River, and the James River is less polluted than it was a couple of decades ago.

10. Rats are similar to mice. Given that mice make great pets, rats probably also make great pets.

Understanding the general form of analogical arguments is important because many analogical arguments contain subarguments. These subarguments provide evidence to support the analogy (the claim that T is like S). In these cases, you must recognize that the evidence for the analogy constitutes the premises in the subargument, not in the main argument.

Consider the following

In April 2010, Arizona signed into law the toughest bill on illegal immigration in generations, making the failure to carry immigration documents a crime. We can expect that New Mexico will soon pass a similar law. After all, New Mexico is a lot like Arizona, given that both have a large population of immigrants and both are bordered by Mexico.

Using the general form for analogical arguments, you can analyze the main argument formally. Notice that the first premise identifies the analogy (T is like S) and the second premise identifies the feature (S has F).

P1:	New Mexico is a lot like Arizona.
P2:	Arizona passed a law making the failure to carry immigration documents a crime.
∴	New Mexico will pass a law making the failure to carry immigration documents a crime.
Issue:	Whether New Mexico will pass a law making the failure to carry immigration documents a crime
S:	Arizona
T:	New Mexico
F :	passing a law making the failure to carry immigration documents a crime

What about the last two claims in the final sentence? Where do they fit? The inference indicator given that signals that they are premises for the first claim in that sentence. That is, they present evidence that New Mexico and Arizona are alike. Thus, the passage contains a subargument, as shown in the following Formal Analysis.

P1:	New Mexico and Arizona have large populations of immigrants.
P2:	New Mexico and Arizona are bordered by Mexico.
∴	New Mexico is like Arizona.

Now, we can diagram the argument.

In April 2010, ① Arizona signed into law the toughest bill on illegal immigration in generations, making the failure to carry immigration documents a crime. We can expect that ② New Mexico will soon pass a similar law. After all, ③ New Mexico is a lot like Arizona, given that ④ both have a large population of immigrants and ⑤ both are bordered by Mexico.

Notice that the main argument has the same structure as the other analogical arguments you have examined. There are two linked premises, one stating the analogy and the other identifying the feature as true of the source. The subargument offers the reasons for the claim that New Mexico really is like Arizona by identifying the ways in which the two analogues are similar.

Understanding the general form for analogical arguments is also helpful when the arguer does not explicitly state the analogy. In these cases, the arguer provides evidence for the analogy, but the analogy itself is missing. Part of the work, then, in analyzing analogical arguments includes identifying the analogy, even when it is not explicitly stated by the arguer.

Analyzing this analogical argument is particularly challenging because neither the analogy nor the conclusion is explicitly stated. However, knowing the general form of analogical arguments can help. First, what is the analogy? James compares banning smoking on campus to banning alcohol and drug use on campus. Next, what feature does he conclude is true of banning smoking based on its being true of banning alcohol and drug use? When he says, “… no one uses them, right? Wrong!” he implies that banning alcohol and drug use on campus has not stopped their consumption. From this, he concludes that banning smoking on campus will not stop smoking. Let’s set out this argument in a Formal Analysis.

P1:	Banning smoking on campus is like banning alcohol and drug use on campus.
P2:	Banning alcohol and drug use on campus does not stop alcohol and drug consumption.
∴	Banning smoking on campus will not stop smoking.
Issue:	Whether banning smoking on campus will stop smoking

Exercise 9.4.

· Your Turn! Identify the source, target, and feature of the argument above.

Exercise 9.5.

Provide a Formal Analysis and diagram of each of the following analogical arguments. Then state the source, target, and feature.

1. Lasagna and spaghetti both have pasta and tomato sauce, so lasagna is like spaghetti. Since spaghetti is tasty, lasagna is probably tasty.

2. A catfish has gills, and a trout has gills. Consequently, catfish are like trout. Now, catfish are able to live only a short while out of water. So trout can probably live only a short while out of water.

3. A prince is the child of a king. A princess, too, is the child of a king. So a prince is like a princess. Also, a princess leads a sheltered life. Thus, a prince most likely leads a sheltered life.

4. Horses, dogs, and cats all can be taught tricks by using positive reinforcement and lots of food treats. Thus, birds are probably trainable in the same way.

5. A DVD is read by a laser beam. A CD is also read by a laser beam. Therefore, a DVD is like a CD. Because a CD must not be scratched, a DVD probably shouldn’t be scratched, either.

6. Astrology studies the stars and has been around for hundreds of years. Astronomy also studies the stars and has been around for hundreds of years. We know that astronomy is worthy of being called a science. Therefore, astrology is likewise worthy of being called a science.

7. Both high school principals and high school counselors have advanced degrees in education. Thus, high school principals are paid more than teachers, since counselors receive more pay than teachers.

8. Since navel oranges have thick rinds, have an acidic core, and are protected by thick leaves and Valencia oranges have similar rinds, acidic cores, and leaf protection, navel oranges are like Valencia oranges. Given that Valencia oranges can withstand a light freeze, navel oranges can be expected to withstand a light freeze as well.

9. The Mississippi River, the Potomac River, and the Hudson River are all bodies of fresh water that flow toward the ocean. So the Nile River probably flows toward the ocean, since it, too, is a body of fresh water.

10. Chimpanzees are highly intelligent, social, and able to use rudimentary tools. Thus, chimpanzees are like mandrills because they, too, are highly intelligent, social, tool-using animals. Because mandrills are capable of learning a simple form of sign language, chimpanzees can probably learn a simple form of sign language, too

11. Eyes are like ears because both eyes and ears are sensitive to outside stimulation and have nerves leading directly to the brain. Thus, since ears give incomplete information about the outside environment, eyes, too, probably give incomplete information about the outside world.

12. We can infer that Utah is much like California because Utah is dry, mountainous, and dependent on water from other states and California is dry, mountainous, and dependent on water from other states. Because California has profited from large-scale drip irrigation of agricultural land, Utah would probably also profit from large-scale drip irrigation of agricultural land.

13. The last three economic recessions were made less damaging to people after Congress passed a stimulus package that gave all taxpayers a few hundred extra dollars to spend. It seems likely, then, that the current economic recession will be made less damaging to people after Congress passes a similar stimulus package.

14. Apple, apricot, and plum trees all need to be pruned after their leaves fall. It stands to reason that peach trees will need to be pruned after their leaves fall.

15. Comedies and musicals are both theatrical performances. Given that musicals incorporate dancing, comedies are likely to incorporate dancing also.

Evaluating Analogical Arguments

When evaluating analogical arguments, you should use the terms appropriate for evaluating inductive arguments. Recall that an inductive argument is strong when the premises make the conclusion very likely to be true. Unlike deductive arguments, which are either valid or invalid, the strength of inductive arguments varies across a continuum from very strong to very weak. This means that assessing the strength of analogical arguments will involve using different criteria than assessing the validity of deductive arguments. The strength of an analogical argument depends on how much and in what ways the target is like the source. So, to evaluate an analogical argument, you must consider three things: the quantity of similarities shared between the source and target, the number of analogies presented, and the relevance of the similarities to the feature.

First, how many similarities between the source and target does the arguer identify? The more relevant similarities shared by the source and target, the stronger the argument. This is because the more characteristics the analogues have in common, the more likely it is that they will have an additional characteristic in common. To see this, compare a pair of analogical arguments. First, consider this one.

Ron and Brian both like the movie Shaun of the Dead. Since Ron also likes the movie Zombieland, Brian will, too.

Notice that this argument contains a subargument. Analyzed formally, with the subargument presented first, as always, the argument looks like this.

P:	Ron and Brian both like the movie Shaun of the Dead.
∴	Brian is like Ron.
P1:	Brian is like Ron.
P2:	Ron likes the movie Zombieland.
∴	Brian will like the movie Zombieland.
Issue:	Whether Brian will like the movie Zombieland

Now identify the source, target, and feature.

S:	Ron
T:	Brian
F:	likes the movie Zombieland.

Compare that argument to this one.

Ron and Brian both like the movies Evil Dead 2, Day of the Dead, Army of Darkness, and Shaun of the Dead. Since Ron also likes the movie Zombieland, Brian will, too.

Notice that this argument also contains a subargument. Analyzed formally, the argument looks like this.

P:	Ron and Brian both like the movies Evil Dead 2, Day of the Dead, Army of Darkness, and Shaun of the Dead.
∴	Brian is like Ron.
P1:	Brian is like Ron.
P2:	Ron likes the movie Zombieland.
∴	Brian will like the movie Zombieland.
Issue:	Whether Brian will like the movie Zombieland

Exercise 9.6.

· Your Turn! Identify the source, target, and feature of the previous argument.

In both arguments, the source, target, and feature are identical because the main arguments are identical. What differs is the amount of evidence provided in the subargument to support the analogy. In the first argument, Ron is like Brian because they both like one movie, and in the second argument, Ron is like Brian because they both like four movies. This means that the second argument is stronger due to the fact that the target and the source share a larger quantity of similarities. It is more probable that Brian will like a particular movie that Ron likes if they both like four other movies than if they both like only one other movie. The more that the analogues have in common, the more probable it is that the conclusion of the argument is true.

Hint!

Be sure that you do not confuse the similarities with the feature. The similarities are those commonalities between the source and target that the arguer presents as reasons to support the analogy. Thus, the similarities are found only in the premises of the subargument. The feature is the characteristic of the source that the arguer concludes is also a characteristic of the target. Thus, the feature is found in one premise and the conclusion of the main argument.

Second, how many analogues does the arguer provide in the source? Generally speaking, the more analogues presented in the source, the stronger the argument. This is because each analogy offers additional evidence to support the conclusion. To see this, compare another pair of analogical arguments. First, consider this one.

I have taken a course in black-and-white photography, and it was interesting and fun. Therefore, I am likely to find a course in fashion photography interesting and fun.

Analyzed formally, the argument looks like this.

P1:	The course in fashion photography is like the course in black-and-white photography.
P2:	The course in black-and-white photography was interesting and fun.
∴	The course in fashion photography will be interesting and fun.
Issue:	Whether the course in fashion photography will be interesting and fun

Now identify the source, target, and feature.

S:	the course in black-and white-photography
T:	the course in fashion photography
F:	interesting and fun

Compare that argument to this one.

I have taken courses in black-and-white photography, color photography, and documentary photography and have found all of them interesting and fun. Therefore, I am likely to find a course in fashion photography interesting and fun.

Analyzed formally, the argument looks like this.

P1:	The course in fashion photography is like the courses in black-and-white photography, color photography, and documentary photography.
P2:	The courses in black-and-white photography, color photography, and documentary photography were interesting and fun.
∴	The course in fashion photography will be interesting and fun.
Issue:	Whether the course in fashion photography will be interesting and fun

Now identify the source, target, and feature.

S:
S:	the courses in black-and-white photography, color photography, and documentary photography
T:	the course in fashion photography
F:	interesting and fun

In both arguments, the target is the course in fashion photography, and the feature is interesting and fun. But notice the difference in the source. The first argument provides only one analogue in the source, whereas the second provides three. Of the two, then, the second is stronger because the source is larger. In the second argument, the speaker enjoyed a wider variety of photography courses, making it more likely that he or she would enjoy another kind of photography course.

Exercise 9.7.

For each of the following pairs of analogical arguments, identify the source, target, and feature. Then determine which argument is stronger in each pair, and explain why.

· A. My Scion xB gets at least 25 miles per gallon, so this Scion xD will also get at least 25 miles per gallon.

· B. The Scion xA gets at least 25 miles per gallon. The Scion xB gets at least 25 miles per gallon. And the Scion tC gets at least 25 miles per gallon. You can, then, expect the Scion xD to get at least 25 miles per gallon.

· A. I have visited Six Flags, Hershey Park, Kings Island, Joyland, and Carowinds, all of which had a wide selection of roller coasters. So I bet Disney World also has a wide selection of roller coasters.

· B. I have visited Six Flags and Hershey Park, both of which had a wide selection of roller coasters. So I bet Disney World also has a wide selection of roller coasters.

· A. Preparing for a final exam requires studying and skill. Preparing for a wrestling tournament also requires study and skill. Since wrestlers do better if they get a good night’s sleep before a match, students taking final exams should also do better on a good night’s sleep.

· B. Preparing for a final exam requires studying, skill, and discipline. Preparing for a wrestling tournament also requires study, skill, and discipline. Since wrestlers do better if they get a good night’s sleep before a match, students taking final exams should also do better on a good night’s sleep.

· A. Gopher snakes have brown markings on their backs, and they are harmless to people. Rattlesnakes also have brown markings on their backs, so they, too, must be harmless to people.

· B. Gopher snakes, Great Plains rat snakes, and eastern hog-nosed snakes all have brown markings on their backs, and they are harmless to people. Rattlesnakes also have brown markings on their backs, so they, too, must be harmless to people.

· A. Commercial airplane flights are long, boring, and cramped. Commercial space flights will also be long, boring, and cramped. People can endure long commercial airplane flights if they are offered movies, food breaks, and space to walk around. Therefore, these options will be useful for commercial space flights.

· B. Commercial airplane flights are long and boring. Commercial space flights will also be long and boring. People can endure long commercial airplane flights if they are offered movies, food breaks, and space to walk around. Therefore, these options will be useful for commercial space flights.

· A. Tigers have strong leg muscles, long legs, loose-fitting skin, and a strong predatory instinct. Cheetahs, too, have strong leg muscles, long legs, loose-fitting skin, and a strong predatory instinct. Since cheetahs are extremely fast runners, tigers are probably also fast runners.

1. B. Tigers have strong leg

· muscles, long legs, and a strong predatory instinct. Cheetahs also have strong leg muscles, long legs, and a strong predatory instinct. Since cheetahs are extremely fast runners, tigers are probably also fast runners.

· A. Lawyers, doctors, engineers, and high school teachers all have advanced degrees. Therefore, high school teachers earn a much higher than average salary, since lawyers, doctors, and engineers earn a much higher than average salary.

· B. Lawyers and high school teachers have advanced degrees. Therefore, high school teachers earn a much higher than average salary, since lawyers earn a much higher than average salary.

· A. People can use email to write informally to close friends and to write formally to strangers. Regular mail also can be used to write informally to close friends and to write formally to strangers. Since using sarcasm in regular mail can lead to misunderstandings, using sarcasm in email can also lead to misunderstandings.

· B. People can use email to write informally to close friends, to write formally to strangers, and to manage various business issues. Regular mail also can be used to write informally to close friends, to write formally to strangers, and to manage various business issues. Since using sarcasm in regular mail can lead to misunderstandings, using sarcasm in email can also lead to misunderstandings.

· A. MySpace and Facebook are both social networking websites that allow users to send messages to one another. Because Facebook is free for all users, MySpace is likely also free for all users.

· B. MySpace and Facebook are both social networking websites that allow users to share information and photographs, as well as to send messages to one another. Because Facebook is free for all users, MySpace is likely also free for all users.

· A. Gwen and Charles are very similar: They are the same age, exercise regularly, eat a well-balanced diet, and have no family history of heart disease. Since Charles has healthy cholesterol levels, Gwen should also.

· B. Gwen and Charles are both 47 years old. Since Charles has healthy cholesterol levels, Gwen should also.

When we discussed the quantity of similarities and analogues, we stated that an analogical argument is stronger when there are more similarities and when there are more analogues. While this is generally true, you must also attend to another criterion—namely, relevance. Why? For any given analogy, there will be numerous ways in which the analogues are similar, so you must consider whether these similarities are in fact relevant to the feature. Only when they are relevant is the conclusion more likely to be true.

Consider, for example, the following analogical argument.

Humans are a lot like rats. They are both mammals, and they both have the same basic physiology. Since rats that are exposed to secondhand smoke have a high risk of developing cancer, humans who are exposed to secondhand smoke have a high risk of developing cancer.

Let’s first analyze and diagram the argument to isolate the similarities from the source, target, and feature.

① Humans are a lot like rats. ② They are both mammals, and ③ they both have the same basic physiology. Since ④ rats that are exposed to secondhand smoke have a high risk of developing cancer, ⑤ humans who are exposed to secondhand smoke have a high risk of developing cancer.

Putting it All Together

Writing a Critical Précis of an Analogical Argument

In Chapters 2, 3, and 4, you learned how to recognize and analyze arguments. In Chapter 5, you also learned how to distinguish among different kinds of arguments. Now that you can evaluate analogical arguments, you can put all of these skills together by adding analogical argument evaluation to your Critical Précis assignments.

Directions for a Critical Précis of an Analogical Argument

In paragraph form, use complete sentences and proper English grammar and spelling to do the following:

Step 1: Identify the passage.

· Completely and correctly identify the author and the source (whenever such information is given).

· If the passage contains an argument, identify it as such. Then move to Step 2.

· If the passage does not contain an argument, identify it as a nonargument. Then specify which feature of an argument is lacking.

Step 2: Analyze the argument.

· Clearly and completely identify the issue, conclusion, and premise or premises in that order.

· If the passage is a multiple argument, write separate paragraphs to analyze each separate argument.

Step 3: Diagram the argument.

· Verify that the diagram is consistent with your Critical Précis.

Step 4: Identify the kind of argument.

· If the argument is deductive, identify it as a categorical argument or a truth-functional argument.

· If the argument is inductive, identify it as an inductive generalization, an analogical argument, or a causal argument.

Step 5: Evaluate the argument.

· If the argument is an analogical argument, evaluate its strength by considering the quantity of similarities identified, the number of analogues presented, and how relevant the similarities are to the feature.

Let’s consider a few examples before you try some on your own.

A woman without a man is like a fish without a bicycle.—Gloria Steinem

First, is this passage an argument? The author gives an analogy by comparing a woman without a man to a fish without a bicycle, presumably to counter assumptions that a woman needs a man. However, notice that there is only one claim here, so it cannot be an argument. The Critical Précis, then, should read as follows:

This passage by Gloria Steinem is not an argument. It contains only one claim, and arguments need at least two claims.

Exercise 9.11.

· Your Turn! Construct an analogical argument by using the analogy given by Gloria Steinem.

Next, consider this passage.

How do we know that animals can feel pain? Because animals are like human beings. The nervous systems of vertebrates, especially of birds and mammals, are fundamentally similar to that of human beings. And, both animals and humans behave in similar ways when injured: writhing, facial contortions, moaning, yelping, avoidance, etc. So, since we know that human beings can feel pain, we can conclude that animals can also.—Peter Singer

Unlike the previous example, this one contains an argument. The arguer uses an analogy (that animals are like humans) to draw a conclusion (that animals can feel pain). Let’s start our analysis by diagramming the argument and then presenting the written analysis. Notice that the diagram and written analysis are consistent.

How do we know that animals can feel pain? Because ① animals are like human beings . ② The nervous systems of vertebrates, especially of birds and mammals, are fundamentally similar to that of human beings . And, ③ both animals and humans behave in similar ways when injured: writhing, facial contortions, moaning, yelping, avoidance, etc . So, since we know that ④ human beings can feel pain , we can conclude that ⑤ animals can also .

7. This passage from Peter Singer contains an argument. The issue is whether animals can feel pain. The conclusion is that animals can feel pain. The first premise is that animals are like humans. The second premise is that humans can feel pain.

8. The passage contains a subargument. The intermediate conclusion is that animals are like humans. The first premise is that the nervous systems of vertebrates, especially of birds and mammals, are fundamentally similar to that of human beings. The second premise is that both animals and humans behave in similar ways when they are injured: writhing, facial contortions, moaning, yelping, avoidance, etc.

9. To evaluate this argument, we must first identify the source, target, and feature. The source, recall, is the analogue mentioned only in the premises, the target is the analogue mentioned in the analogy and conclusion, and the feature is the characteristic that the arguer concludes is true of the target based on its being true of the source. In this argument, the source is humans, the target is animals, and the feature is can feel pain. What about the other claims about their nervous systems and behaviors? These are the similarities that support the claim that animals are like humans. Notice that those characteristics are mentioned only in the premises of the subargument. Now that we have completed this deeper analysis of the argument, we can evaluate it. How strong is the argument? As you can see in the paragraph below, each of the three criteria for evaluating analogical arguments is addressed.

10. This is an inductive analogical argument. There is one analogy presented. Since there are two similarities mentioned (similar nervous systems and similar behavioral responses to injury), there is good support for the analogy. And both similarities are relevant to the feature (can feel pain). Thus, this is a strong argument.

ne Step Further

Analogical arguments are commonly used in law. In the legal debate regarding same-sex marriage, for example, defenders of marriage equality often compare laws prohibiting same-sex marriage to past laws prohibiting interracial marriage. The court case they refer to is Loving v. Virginia (1967), in which the U.S. Supreme Court argued that antimiscegenation laws were ultimately an attempt to perpetuate racial inequality by maintaining racial segregation. Chief Justice Warren delivered the opinion of the Court, which affirmed the freedom to marry as a vital personal right:

Marriage is one of the “basic civil rights of man,” fundamental to our very existence and survival. To deny this fundamental freedom on so unsupportable a basis as the racial classifications embodied in these statutes, classifications so directly subversive of the principle of equality at the heart of the Fourteenth Amendment, is surely to deprive all the State’s citizens of liberty without due process of law. The Fourteenth Amendment requires that the freedom of choice to marry not be restricted by invidious racial discriminations. Under our Constitution, the freedom to marry, or not marry, a person of another race resides with the individual and cannot be infringed by the State.

1. How are laws prohibiting same-sex marriage similar to laws prohibiting interracial marriage? Which of these similarities are relevant? Why?

2. Construct an analogical argument incorporating the relevant similarities you identified in your answer to the above question.

3. How are laws prohibiting same-sex marriage different from laws prohibiting interracial marriage? Do these differences weaken the argument you constructed? Why or why not?

Bettmann/Corbis

In a 2007 interview, Mildred Loving (pictured here with her husband) stated: “I believe all Americans, no matter their race, no matter their sex, no matter their sexual orientation, should have that same freedom to marry. Government has no business imposing some people’s religious beliefs over others. I support the freedom to marry for all. That’s what Loving, and loving, are all about.”