Avoiding Logical Fallacies
Chapter
Finding and Refuting Logical Fallacies
Logical fallacies (sometimes called rhetorical fallacies) are errors in reasoning. They are like tricks or illusions of thought, and they’re often very sneakily used by politicians and the media to fool people. They are not always easy to spot, and we often commit them accidentally. Sometimes an arguer will commit these fallacies on purpose with the intent of fooling or manipulating the audience. But more often, we make these mistakes accidentally, with the best of intentions. Spotting them in our own arguments and in the arguments of others is a superpower that can help you strengthen your analytical toolkit. Like the doctor with her microscope in Image 4.8, we can closely examine the reasons and evidence writers are using to convince us to believe or do something and decide if their logic is solid.
A fallacy is not just a false fact—it is a flawed structure of claim + reason + evidence that does not make sense together. In fact, a writer can say an idea that may be true but use illogical support. Some fallacies are actually bad logic: they are a syllogism that is missing a piece. Some are actually just pathos or ethos being used in place of logos. This is tricky because good argument writing is supposed to use pathos and ethos in addition to logos. Using these persuasive appeals is not in itself a flaw in logic. However, if your opponent’s argument is pretending to be logical but is actually based only on ethos or pathos, you can refute their claims by pointing out that they are not supporting them with good logic.
You can find many ways people have named, categorized, and analyzed long lists of possible mistakes in logic. Sometimes one flawed argument can be an example of more than one fallacy. It is not always clear how to name one flawed argument. That’s OK! It is worthwhile to examine arguments and look for possible flaws, even if they don’t all have a clear label.
12 Most Common Fallacies
Fallacies that misuse appeals to ethos
These fallacies happen when the writer focuses on who is the source of the idea. We are asked to believe the idea because we believe the source, not because there is solid evidence.
Appeal to false authority: using the opinion of an authority figure or institution of authority in place of an actual argument, especially when the person or group is not an expert on the topic. Often the claimed expert (a) doesn’t have enough background/credentials in the relevant field, (b) disagrees with most experts in the field, or (c) is biased, e.g., has a financial stake in the outcome.
Examples
- Dr. X is an engineer, and he doesn’t believe in global warming. Therefore global warming is not real.
- My favorite basketball player wears a certain brand of shoes, so I should, too.
Ad hominem: (opposite of appeal to authority) attacking the person making an argument rather than the argument itself.
Example
Bandwagon fallacy/appeal to popularity: using the fact that many people do or believe something to say that it is true/right. The name “bandwagon” comes from the idiom “jump on the bandwagon,” perhaps from the tradition of children running after a wagon with musicians playing music at public events, such as the one in Figure 5.7.2. Note: this can be considered an appeal to ethos because it depends on our trust of other people. Some would also categorize this as using an appeal to pathos, because it uses our desire to belong to the crowd to get us to do or believe something.
Example
Appeal to tradition: saying that something has always been done one way, so that’s the right way. Note: Some would also categorize this as using an appeal to pathos because it uses our emotional attachment to customs or elders to get us to do or believe something.
Example
Fallacies that misuse appeals to pathos
These fallacies substitute logic for appeals to fear, anger, pity, love, or the human desire to belong and have other people like us.
Appeal to emotion: Trying to get an emotional response instead of making a valid argument. Note: using appeals to pathos is important in good writing when used in a balanced way along with ethos and logos.
Examples
- An advertisement shows a group of young adult models beaming with joy, playing with an adorable puppy, and all wearing the same brand of jeans.
- Without this additional insurance, you could find yourself broke and homeless.
Slippery slope: making an unsupported or inadequately supported claim that one thing inevitably leads to another: If we allow A to happen, then Z will consequently happen too; therefore, A should not happen. This may be considered a fallacy of logos as well as pathos, but it is placed in this section because it often evokes the emotion of fear. The name comes from the idea of something sliding down a slippery hill, unable to stop.
Example
Fallacies that misuse logos
Circular reasoning/begging the question: One of the premises is the same as the claim that you are trying to prove. This is common in situations where people have an assumption that is very ingrained and, therefore, taken in their minds as a given.
Example
Anecdotal evidence/hasty generalization: using personal experience or an isolated example instead of a valid argument, especially to dismiss statistics. An anecdote is a little story. Hasty means doing something too fast and not carefully.
Example
False cause/post hoc: (a special type of anecdotal evidence/hasty generalization) Assuming that because two events are related, one is the cause of the other. Sometimes, two events are related by coincidence; sometimes, a third factor causes both of the events to happen. Superstitions are good examples of the post hoc fallacy. The term post hoc is from the Latin post hoc ergo propter hoc: after this, therefore because of this. This one is tricky because if one event causes another, they will also be correlated. But just because they are correlated does not prove that one caused the other.
Example
Many residents of the town got sick after drinking soda at the festival, so the chemicals in the soda must have made them sick. (It could be a virus, or food poisoning, or another cause).
False dilemma/false dichotomy: The writer presents two choices as the only possibilities when, in fact, more possibilities exist.
Example
False analogy: The writer says that one situation is like another when they may have something in common but really aren’t alike to show that they should have the same solution or action. We sometimes use the idiom “comparing apples and oranges” (see Figure 5.7.4) to describe this fallacy, especially when discussing statistics.
Example
Straw man: The writer misrepresents someone’s argument to make it easier to attack. They may choose only the opponent’s weakest point or even lie about what the opponent said to make themselves look more reasonable. If you have ever been in an argument with a friend or relative and said, “…but I never said that!” then you have pointed out a straw man fallacy. The origin of this term is from a scarecrow (see figure 5.7.5): a traditional farming practice of setting up a human figure made out of dried grass to scare birds away from crops. Imagine that the writer is supposed to be showing a real fight between two people, but instead sets up a fake man made out of dried grass and then knocks it down.
Example
Explaining and responding to logical fallacies
When you find a logical fallacy in an opponent’s argument, you can use the following pattern to name, explain, and refute it. This pattern also works for responding to other kinds of counterarguments, even if they do not contain obvious logical fallacies that are easy to identify.
- Sentence 1:
- Name your opponent/the source of the fallacy
- Use a special reporting expression to show you don’t believe them or doubt their logic
-
paraphrase/summarize what they said. Usually, the paraphrase/summary will be in cause-effect form (they want us to do or believe x because y). You may have to think more deeply about what their argument really is because if someone is using a logical fallacy, they usually don’t explain their argument completely, or else it would be obvious that it doesn’t make sense.
- Sentence 2:
- Transition to your rebuttal with connecting words
- rename your opponent/the source of the fallacy
- use a special reporting verb phrase
- name the logical fallacy (or if there isn’t a clear label for it, you can just say that their logic is flawed).
- Sentence 3: explain the error
Examples
- One critic of further smoking restrictions wants to convince us that tobacco use is not actually unhealthy, based on the fact that his grandmother smoked for 80 years and did not get cancer. Clearly, this author is engaging in the anecdotal evidence fallacy. Just because this one smoker escaped the harms of tobacco use doesn’t mean that, statistically, smoking is a safe practice.
- The advertisers imply that if we buy their brand of jeans, we will experience the same joy and beauty as the group of young people with their puppy. On closer inspection, this marketing campaign is engaging in a manipulative appeal to emotion. They provide no evidence that their product is actually higher quality than any other brand.
Language for Responding to Logical Fallacies
| Part of your sentence | Suggested language patterns |
|---|---|
| Sentence 1:
source
of the fallacy |
|
| special reporting verb phrase |
|
|
paraphrase
/summary of their argument |
|
| Sentence 2: transition to your rebuttal |
|
| rename the
source
(opponent) |
|
| special verb |
|
| name the fallacy/error |
|
| Sentence 3: explain the error |
|
