Unit 7: Informal fallacies

Introduction to informal fallacies

Activity 1: Reading

Read this introduction to understand more about informal fallacies.

Informal fallacies are caused by problems in the reasoning, that is the jump from the premises to the conclusion. Although there are many ways to categorize informal fallacies, in this course they are categorised into four broad groups, namely:

• red herring fallacies
• causal fallacies (non causa pro causa)
• vagueness and ambiguity
• weak analogy

Each of these groups of informal fallacies are introduced in turn in this unit.

Red herring fallacies

Activity 2: Reading

Read carefully and consider the following informal fallacies. To understand a fallacy, you need to think.

There will be no understanding without actually thinking. PowerPoint and YouTube are useful tools, but the most important resource is your brain!

Fallacies that aim to distract attention are known as red herring fallacies. Red herring is a very pungent, or smelly, fish that could be used to distract dogs from the scent of a trail. This is probably the original of the name of this fallacy. Red herring fallacies include straw man, genetic fallacy, bandwagon fallacy (ad populum), emotional appeal (rhetorical ploy), wishful thinking, ad hominem, tu quoque, appeal to authority, black or white fallacy (false dilemma, false dichotomy), special pleading, no true Scotsman, the fallacy fallacy, gambler`s fallacy.

• Strawman:  Misrepresenting someone's argument to make it easier to attack.
• Special pleading:  You moved the goalposts or made up an exception when your claim was shown to be false.
• The gambler's fallacy You said that ‘runs’ occur (like getting 7 red numbers in a row at a roulette table), not realizing that each spin (event) is completely independent.
• black-or-white (aka. False dilemma, False dichotomoy):  You presented two alternative states as the only possibilities, when in fact more possibilities exist (the "grey area")
• Ad hominem (aka. personal attack:  You attacked your opponent’s character or personal traits in an attempt to undermine their argument.  Politicians do this frequently (among many logical fallacies, of course).
• Bandwagon (aka. ad populum):  You appealed to popularity or the fact that many people do something as an attempted form of validation.
• Tu quoque:  You avoided having to engage with criticism by turning it back on the accuser.  You answered criticism with criticism.
• Appeal to emotion: [= rhetorical ploy] You attempted to manipulate an emotional response in place of valid or compelling argument.
• Appeal to authority:  You said that because an authority thinks something, therefore it must be true.
• No true Scotsman:  You made what could be called an appeal to purity as a way to dismiss relevant criticisms or flows of your argument.
• Fallacy fallacy:  You presumed that because a claim has been poorly argued, or a fallacy has been made, that the claim itself must be wrong.

Activity 3: Watching

Watch this excellent video introducing a number of informal fallacies with easy-to-follow examples.

Causal fallacies (non causa pro causa)

Activity 4: Thinking

Consider the following fallacies carefully.

• False cause  You presumed that a real or perceived relationship between things means that one is the cause of the other. - This fallacy is very general and includes the specific fallacies listed below.
• Non causa pro causa: (Literally; "Not the cause for the cause") A formal way to say false cause
• Post hoc, ergo propter hoc : (Literally: "After this, therefore because of this") You presumed that a real or perceived relationship between two sequential events means that the first one is the cause of the other.
• Cum hoc, ergo propter hoc : (Literally: "With this, therefore because of this") You presumed that a real or perceived relationship between two happening at the same time, and presume that one is the cause of the other.

Activity 5: Post-hoc ergo propter hoc in a US televsion drama 

Vagueness and ambiguity

Activity 6: Thinking

Consider the following fallacies carefully.

• Slippery slope:  You said that if we allow A to happen, then Z will eventually happen too, therefore A should not happen.
• Appeal to nature:  You argued that because something is natural, it is therefore valid, justified, inevitable, good, or ideal.
• Ambiguity:  You used a double meaning or ambiguity of language to mislead or misrepresent the truth.
• Middle ground:  You claimed that a compromise, or middle point, between two extremes must be the truth.

Weak analogy

Activity 7: Thinking

Consider the following fallacies carefully.

• Anedotal:  You used a personal experience or an isolated example instead of a sound argument or compelling evidence.
• Texas sharpshooter:  You cherry-picked a data cluster to suit your argument. or found a pattern to fit a presumption.  (Example:  Climate change deniers zooming in on a small part of the graph and ignoring the trend in the entire data set.)
• Weak analogy: Analogies use inductive reasoning to compare features of two similar elements. Analogies may be true comparing features of, say, chimpanzees and monkeys; but the more dissimiliar the items, the less reliable the analogy is.
• Unrepresentative sample: This occurs when the sample is not representative of the population to be generalized to. For example, if I generalize from my family situation (2 adults, 2 children), to the population of Japan, I can assume that half of the adults are Japanese and all the children are female, which is obviously incorrect.
• Hasty generalization: All conclusions using inductive reasoning may be judged as generalizations. However, a hasty generalization is one that is reached quickly, and so inductive reasoning used without careful consideration may be described as falling victim to the fallacy of hasty generalization.
• Misleading statistics:You use statistics inappropriately as evidence. Common issues include using statistics that are biased, statistics that are cherry-picked, and statistics that do not relate to the claim.

Twenty-four fallacies

The twenty-four fallacies is the most popular set of fallacies that are taught in universities worldwide. There is a free downloadable colour poster and an interactive website that can help you. The texts are written for native speakers of English, so the vocabulary may be challenging at times. Just use a dictionary to look up the meanings of any unknown words.

Activity 8: Reading

Read the following fallacies extracted from the website above and try to classify them into categories. You can use the four categories presented in this unit or your own categories.

1. Strawman:  Misrepresenting someone's argument to make it easier to attack.
2. Slippery slope:  You said that if we allow A to happen, then Z will eventually happen too, therefore A should not happen.
3. Special pleading:  You moved the goalposts or made up an exception when your claim was shown to be false.
4. The gambler's fallacy You said that ‘runs’ occur (like getting 7 red numbers in a row at a roulette table), not realizing that each spin (event) is completely independent.
5. black-or-white (aka. False dilemma, False dichotomoy):  You presented two alternative states as the only possibilities, when in fact more possibilities exist (the “grey area”)
6. False cause:  You presumed that a real or perceived relationship between things means that one is the cause of the other.
7. Ad hominem (aka. personal attack:  You attacked your opponent’s character or personal traits in an attempt to undermine their argument.  Politicians do this frequently (among many logical fallacies, of course).
8. Loaded question:  You asked a question that had a presumption built into it so that it couldn't be answered without appearing guilty.
9. Bandwagon (aka. ad populum):  You appealed to popularity or the fact that many people do something as an attempted form of validation.
10. Begging the question:  You presented a circular argument in which the conclusion was included in the premise.  (Example:  The Bible is true because God exists, and God exists because the Bible says so, therefore the Bible is true since God exists…)
11. Appeal to authority:  You said that because an authority thinks something, therefore it must be true.
12. Appeal to nature:  You argued that because something is natural,it is therefore valid, justified, inevitable, good, or ideal.
13. Composition/Division: [ = invalid references] You assumed that one part of something has to be applied to all, or other, parts of it; or that the whole must apply to its parts.
14. Anecdotal:  You used a personal experience or an isolated example instead of a sound argument or compelling evidence.
15. Appeal to emotion: [= rhetorical ploy ] You attempted to manipulate an emotional response in place of valid or compelling argument.
16. Tu quoque:  You avoided having to engage with criticism by turning it back on the accuser.  You answered criticism with criticism.
17. Burden of proof:  You said that the burden of proof lies not with the person making the claim, but with someone else to disprove. Extraordinary claims require extraordinary evidence.
18. No true Scotsman:  You made what could be called an appeal to purity as a way to dismiss relevant criticisms or flows of your argument.
19. Texas sharpshooter:  You cherry-picked a data cluster to suit your argument, or found a pattern to fit a presumption.  (Example:  Climate change deniers zooming in on a small part of the graph and ignoring the trend in the entire data set.)
20. Fallacy fallacy:  You presumed that because a claim has been poorly argued, or a fallacy has been made, that the claim itself must be wrong.
21. Personal incredulity:  Because you found something difficult to understand, or are unaware how it works, you made out like it is probably not true.  (Example: Donald does not understand how the tides work, and therefore God did it.)
22. Ambiguity:  You used a double meaning or ambiguity of language to mislead or misrepresent the truth.
23. Genetic:  You judged something as either good or bad on the basis of where it comes from, or from whom it came.
24. Middle ground:  You claimed that a compromise, or middle point, between two extremes must be the truth.

Activity 9: Reading

Use the following website to practise naming the fallacies.

Activity 10: Latinate fallacies

Recall these fallacies from their Latin names.

1. Post hoc ergo propter hoc
2. Cum hoc ergo propter hoc
3. Non causa pro causa
4. Ad hominem
5. Tu quoque
6. Ad populum

Activity 11: Revision

Work alone or with a partner. Describe and provide examples for each fallacy.

The translations were created by students. If you have any better suggested translations, please contact your tutor.

Activity 12: Identifying fallacies

Work alone or in pairs. Identify the fallacy in each of the following arguments.

1. We are not alone in the universe. There is intelligent life in space. I don't have any proof. But you don't have any proof that there is not, so there is life in space.
2. You have to make a choice. It's either study hard for the exam or give up. Make your choice now.
3. If Andy is running then he is moving. Andy is moving. Therefore, he is running.
4. All lions are animals. All cats are animals. Therefore, all lions are cats.
5. We all know why the Dean supports this project. And it is not because he wants to help students. I won't say anything else
6. A recent survey of stduent opinion reported that 73 percent thought cheating should be allowed.
7. The court found the defendant guilty of murder. The defendant is a murderer. Therefore, the court found him guilty.
8. Professor X stated that there is no need to invest time and money on improving English, but he cannot even speak English!
9. Professor X realized that each year once the snow melts, new students arrived in his laboratory, so he concluded that snow melt causes student arrivals.
10. Professor X graduated from Tokyo University so what he says must be correct.

Knowledge and application

Activity 13: Slideshow and video

Work alone. Create a narrated slideshow with three slides for ONE fallacy: slide 1 - name of fallacy, slide 2 - example of fallacy, slide 3 - explanation of fallacy. Submit the slideshow(s) through ELMS in two formats: slideshow (e.g. pptx, key) and video (In PowerPoint and Keynote, there is an export to video option). The best submissions will be uploaded to this website. Feel free to include (or omit) your name (and photo?) in the slideshow.