Recognizing Enthymemes

An enthymeme is a syllogism with one or two parts of its argument—usually, the major premise—missing. In everyday life, we often leave out parts of arguments—most of the time because we think they are so obvious (or clearly implied) that they don’t need to be stated. We assume that the people hearing or reading the arguments will easily be able to fill in the missing parts.

Many enthymemes are presented as a conclusion plus a reason. Consider the following enthymeme:

Robert has lied, so he cannot be trusted.

In the statement above, the minor premise and the conclusion are stated, but the major premise is only implied. Once the missing term has been supplied, the logical structure of the enthymeme becomes clear:

MAJOR PREMISE People who lie cannot be trusted.
MINOR PREMISE Robert has lied.
CONCLUSION Therefore, Robert cannot be trusted.

It is important to identify enthymemes in arguments you read because some writers, knowing that readers often accept enthymemes uncritically, use them intentionally to unfairly influence readers.

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Consider this enthymeme:

Because Liz receives a tuition grant, she should work.

Although some readers might challenge this statement, others will accept it uncritically. When you supply the missing premise, however, the underlying assumptions of the enthymeme become clear—and open to question:

MAJOR PREMISE All students who receive tuition grants should work.
MINOR PREMISE Liz receives a tuition grant.
CONCLUSION Therefore, Liz should work.

Perhaps some people who receive tuition grants should work, but should everyone? What about those who are ill or who have disabilities? What about those who participate in varsity sports or have unpaid internships? The enthymeme oversimplifies the issue and should not be accepted at face value.

At first glance, the following enthymeme might seem to make sense:

North Korea is ruled by a dictator, so it should be invaded.

However, consider the same enthymeme with the missing term supplied:

MAJOR PREMISE All countries governed by dictators should be invaded.
MINOR PREMISE North Korea is a country governed by a dictator.
CONCLUSION Therefore, North Korea should be invaded.

Once the missing major premise has been supplied, the flaws in the argument become clear. Should all nations governed by dictators be invaded? Who should do the invading? Who would make this decision? What would be the consequences of such a policy? As this enthymeme illustrates, if the major premise of a deductive argument is questionable, then the rest of the argument will also be flawed.

BUMPER-STICKER THINKING

Bumper stickers often take the form of enthymemes:

  • Self-control beats birth control.

  • Peace is patriotic.

  • A woman’s place is in the House . . . and in the Senate.

  • Ban cruel traps.

  • Evolution is a theory—kind of like gravity.

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  • I work and pay taxes so wealthy people don’t have to.

  • The Bible says it, I believe it, that settles it.

  • No one needs a mink coat except a mink.

  • Celebrate diversity.

Most often, bumper stickers state just the conclusion of an argument and omit both the major and minor premises. Careful readers, however, will supply the missing premises and thus determine whether the argument is sound.

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Bumper stickers on a car.
© Dave G. Houser/Corbis.

EXERCISE 5.1

Read the following paragraph. Then, restate its main argument as a syllogism.

Drunk Driving Should Be Legalized

In ordering states to enforce tougher drunk driving standards by making it a crime to drive with a blood-alcohol concentration of .08 percent or higher, government has been permitted to criminalize the content of drivers’ blood instead of their actions. The assumption that a driver who has been drinking automatically presents a danger to society even when no harm has been caused is a blatant violation of civil liberties. Government should not be concerned with the probability and propensity of a drinking driver to cause an accident; rather, laws should deal only with actions that damage person or property. Until they actually commit a crime, drunk drivers should be liberated from the force of the law. (From “Legalize Drunk Driving,” by Llewellyn H. Rockwell Jr., WorldNetDaily.com)

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EXERCISE 5.2

Read the following paragraphs. Then, answer the questions that follow.

Animals Are Equal to Humans

According to the United Nations, a person may not be killed, exploited, cruelly treated, intimidated, or imprisoned for no good reason. Put another way, people should be able to live in peace, according to their own needs and preferences.

Who should have these rights? Do they apply to people of all races? Children? People who are brain damaged or senile? The declaration makes it clear that basic rights apply to everyone. To make a slave of someone who is intellectually handicapped or of a different race is no more justifiable than to make a slave of anyone else.

The reason why these rights apply to everyone is simple: regardless of our differences, we all experience a life with its mosaic of thoughts and feelings. This applies equally to the princess and the hobo, the brain surgeon and the dunce. Our value as individuals arises from this capacity to experience life, not because of any intelligence or usefulness to others. Every person has an inherent value, and deserves to be treated with respect in order to make the most of their unique life experience. (Excerpted from “Human and Animal Rights,” by AnimalLiberation.org)

  1. What unstated assumptions about the subject does the writer make? Does the writer expect readers to accept these assumptions? How can you tell?

  2. What kind of supporting evidence does the writer provide?

  3. What is the major premise of this argument?

  4. Express the argument that is presented in these paragraphs as a syllogism.

  5. Evaluate the syllogism you constructed. Is it true? Is it valid? Is it sound?

EXERCISE 5.3

Read the following five arguments, and determine whether each is sound. (To help you evaluate the arguments, you may want to try arranging them as syllogisms.)

  1. All humans are mortal. Max is human. Therefore, Max is mortal.

  2. Alison should order eggs or oatmeal for breakfast. She won’t order eggs, so she should order oatmeal.

  3. The cafeteria does not serve meat loaf on Friday. Today is not Friday. Therefore, the cafeteria will not serve meat loaf.

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  4. All reptiles are cold-blooded. Geckos are reptiles. Therefore, geckos are cold-blooded.

  5. All triangles have three equal sides. The figure on the board is a triangle. Therefore, it must have three equal sides.

EXERCISE 5.4

Read the following ten enthymemes, which come from bumper stickers. Supply the missing premises, and then evaluate the logic of each argument.

  1. If you love your pet, don’t eat meat.

  2. War is terrorism.

  3. Real men don’t ask for directions.

  4. Immigration is the sincerest form of flattery.

  5. I eat local because I can.

  6. Don’t blame me; I voted for the other guy.

  7. I read banned books.

  8. Love is the only solution.

  9. It’s a child, not a choice.

  10. Think. It’s patriotic.