In this lesson, you will learn how to recognize faulty forms of argumentation and the reasons why these argument forms are unreliable.
What Is a Logical Fallacy?
Each of the argument forms listed above is a useful, legitimate way to attempt to establish the truth of a claim. However, many writers and speakers also knowingly or unwittingly employ logical fallacies, faulty forms of argumentation that provide no support for the conclusion they purport to establish.
On the surface, the fallacies and the legitimate arguments can very similar, but a closer reading will reveal that the fallacies make crucial missteps that undermine their argumentative force.
Learning to distinguish between fallacious arguments and credible ones is the heart and soul of rhetorical analysis, which is a crucial component of both oral and written criticism.
1. Appeals to Emotion
One of the most common logical fallacies is the appeal to emotion, in which a speaker abandons sound reasoning and the presentation of evidence in favor of statements that tug at the heartstrings or exploit sentiment.
Question
A hypothetical radio commercial attempts to solicit donations to fight hunger among children. Which of the following statements from the ad uses a fallacious appeal to emotion?
- Your money will help repair farming infrastructure and foster agricultural self-sufficiency.
- You can make a real difference in these children’s lives without subjecting yourself to any financial hardship.
- Just one look at these hungry children should be enough to inspire you to make a generous contribution.
- In a world of plenty, there is no reason for anyone to go hungry, and your donation will be used to get food to the people who need it most.
Reveal Answer
Choice C is the lone non-argument of the above four statements. Images of hungry children do not constitute a reason to give money to a particular charity. Each of the other three statements logically supports making donation.
2. Argument Ad Populum
Closely related to—and just as common as—the appeal to emotion is the fallacious argument ad populum. Meaning literally an argument “to the people,” an argument ad populum appeals to the popularity of an idea or to the potential of an idea or a product to make one popular as a reason to accept the truth of a conclusion.
Arguments ad populum are fallacious because the fact that an idea or conclusion is popular and widely held is not a reason to believe that it is true. In the realm of commercial advertising, the argument ad populum has been refined to a science.
These are only two of the numerous types of logical fallacies, enumerated here because of the frequency with which they appear in speeches and writing. For the remainder of this lesson, we will focus on the fallacious counterparts to the previously discussed legitimate argument forms.
Some Common Logical Fallacies
1. The Fallacy of False Cause
Any argument that presumes a causal relationship without offering reasons to support it is committing the fallacy of false cause.
It is difficult to argue successfully that a relationship of cause and effect exists in this fallacy. The fact that two events occur in close proximity to each other is not reason in itself to assert that one caused the other.
A particularly common form of the false-cause fallacy is known as an argument post hoc ergo propter hoc. Latin for “after this, therefore because of this,” this fallacious argument asserts, without evidence, that the fact that one event occurred earlier in time than a second event means the first event caused the second one.
See if you can spot the difference.
Question
Which of the following is an example of an argument that commits the fallacy of false cause?
- Tuesday morning I did volunteer work. Tuesday afternoon I won the lottery. Therefore, I won the lottery because I did volunteer work.
- Monday night I ate raw beef. Tuesday morning I got food poisoning. Therefore, I got food poisoning because I ate raw beef.
- Thursday morning I put a sign in front of my store advertising a 50 percent price break on shovels. By Thursday afternoon I had sold out of shovels. Therefore, I sold out of shovels because I put that sign in front of my store.
- Saturday night I smoked fourteen cigarettes. Sunday morning I was coughing and short of breath. Therefore, I was coughing and short of breath because I smoked those cigarettes.
Reveal Answer
Choice A is the argument that relies on false cause. It is impossible to articulate a logical connection between doing volunteer work and winning the lottery. In each of the other three choices, the possible connection between the two events is clear.
2. False analogy
An argument uses a false analogy if it compares as similar two objects or situations that in reality are quite different. An argument by analogy must establish relevant similarities between the items it is comparing before its comparison can carry persuasive weight.
Even an argument that identifies similarities between the items it is comparing can be fallacious if the similarities do not connect to the main point of the argument.
Question
See if you can pick out the false analogy from these four choices:
- David and Brian are both two year old boys, and David likes Blue’s Clues, so Brian probably likes Blue’s Clues, too.
- Both Aquaviva and Drop are bottled waters. Aquaviva has a slightly sweet aftertaste, so Drop is likely to have a slightly sweet aftertaste.
- Sarah and Amy are both on the cheerleading team, and Sarah has to be at the stadium by 6:30 on Friday night, so Amy also probably needs to be at the stadium by 6:30 on Friday.
- Brazil and Colombia are both countries in South America, and it rains a lot in Brazil, so it must rain a lot in Columbia, too.
Reveal Answer
Choices A, B, and C are all legitimate arguments by analogy because they have identified a salient common feature of the two items they’re comparing and have used that feature as the basis of their prediction. Age and gender definitely affect TV preferences. A water’s type definitely impacts its aftertaste. Being a cheerleader definitely impacts the likelihood of being obligated to be at a stadium.
Choice D is a false analogy because it fails to establish that being located on the same continent increases the likelihood that two countries have similar weather patterns. The argument ignores other more important factors, such as proximity to an ocean or mountain range, altitude, and average temperature.
3. Improper Appeal to Authority
Improper Appeal to authority is an argument in which a speaker claims that a conclusion should be accepted as true simply because a person who has no special knowledge of the claim says it is true.
In the previous lesson, the following was cited as an example of a legitimate appeal to authority:
People should wash their hands regularly because doctors say doing so prevents disease.
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This is a legitimate appeal to authority because doctors have specialized knowledge of what causes diseases to spread. It makes sense for this argument to refer to the consensus opinion of doctors.
Contrast that argument with this one:
You should buy a Honda the next time you buy a car. The doctor who lives across the street told me Honda makes the best cars.
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This is an improper appeal to authority because we have no reason to believe that a medical doctor is particularly knowledgeable about automotive manufacturing.
The key difference between a legitimate argument by authority and a fallacious one is the relationship between the authority’s area of expertise and the subject matter of the argument.
Question
Which one of the following arguments invokes an improper appeal to authority?
- It is wrong for the county voters to spend $60 million on this highway construction plan. The chair of the university’s Center for Urban Planning is convinced that rapid population growth will render the highway obsolete before construction is even finished.
- We should get a cab home from the club tonight. Celeste’s brother is a police officer, and he said that neighborhood is too dangerous for us to be walking around at night.
- We should buy stock in Luminant Medical Technology. My real-estate broker told me that company’s on the verge of inventing a new x-ray machine that would be a huge boost to their earnings.
- The next time you go to buy a major appliance like a refrigerator or an air-conditioner, you should buy it at Nelson’s Department Store. I read in Consumer Lookout magazine that Nelson’s has the best prices and the best rebates.
Reveal Answer
Choice C is an improper appeal to authority. Real-estate brokers have specialized knowledge of the real-estate market, not the stock market. To be credible, this argument would need to cite a stockbroker, investment banker, or some other financial market professional.
Review
- A logical fallacy is a faulty form of argumentation that provides no support for the conclusion it purports to establish.
- An appeal to emotion is a logical fallacy in which the speaker abandons sound reasoning and the presentation of evidence in favor of statements that tug at the heartstrings or exploit sentiment.
- An argument ad populum is a fallacious argument that appeals to the popularity of an idea or to the potential of an idea or a product to make one popular as a reason to accept the truth of a conclusion.
- The fallacy of false cause is an argument that presumes a causal relationship without offering evidence to support the existence of that relationship.
- Post hoc ergo propter hoc, Latin for “after this, therefore because of this,” is the term for a fallacious argument that asserts, without evidence, that the fact that one event occurred earlier in time than a second event means the first event caused the second one.
- A false analogy is a fallacious argument that compares as similar two objects or situations that in reality are quite different.
- Improper appeal to authority is a fallacious argument in which a speaker claims that a conclusion should be accepted as true simply because a person who has no special knowledge of the claim says it is true.
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