Chapter 4. Errors in Reasoning: Where We Go Wrong
Practice Exercises: Chapter 4
Group 1: Linguistic Obstacles
Identify whether the problem in each sentence is Vagueness (fuzzy boundaries) or Ambiguity (multiple distinct meanings).
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“I saw a bat in the park yesterday.”
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“The new law will require a ‘substantial’ increase in safety protocols for all small businesses.”
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“She is looking for a match.”
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“We need to ensure that students receive a ‘decent’ education before they graduate.”
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“The professor said he would give a talk about the problem of student debt in the library.” (Does he mean the debt is in the library, or the talk is in the library?)
Group 2: Fallacies of Irrelevant Support
Identify the specific fallacy: Ad Hominem (Personal Attack or Circumstantial), Genetic Fallacy, Poisoning the Well, Appeal to the Masses, or Appeal to Tradition.
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“We should keep the current school start time at 7:00 AM. That’s the way this district has done it for fifty years, and there’s no reason to change it now.”
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“Don’t bother listening to Mr. Miller’s argument for public transportation. He doesn’t even own a car, so of course he wants the city to pay for his bus rides.”
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“Before my opponent speaks, I’d like to remind the audience that he has been a paid lobbyist for the tobacco industry for years. Can we really trust anything he says tonight?”
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“You shouldn’t believe in the theory of evolution. After all, Darwin first came up with the idea while watching birds on a tiny island, and how much could he really know back then?”
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“Everyone at Green River College is using this new study app, so it must be the most effective way to learn.”
Group 3: Fallacies of Inadequate or Assumed Support
Identify the specific fallacy: Hasty Generalization, False Cause (Post Hoc), Appeal to Ignorance, Begging the Question, False Dilemma, or Slippery Slope.
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“I wore my lucky socks today and then I passed my logic quiz. Those socks clearly help me think better.”
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“Either you support the new tax increase for schools, or you don’t care about the future of our children.”
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“If we allow the city to install one speed camera on Main Street, they will eventually put them on every corner, track our every move, and turn our town into a police state.”
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“No one has ever proven that ghosts don’t exist; therefore, it is reasonable to believe they are real.”
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“Freedom of speech is important because people should be able to say whatever they want.”
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“I tried one sushi roll and it was terrible. I guess I just don’t like Japanese food.”
Group 4: Rhetorical Devices (Persuaders)
Identify the rhetorical device used: Euphemism, Dysphemism, Weaseler, Downplayer, or Proof Surrogate.
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“The company isn’t ‘firing’ anyone; they are merely ‘right-sizing’ the department to improve efficiency.”
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“It is possible that the new policy might lead to some minor inconveniences for a few people.”
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“He’s just a so-called expert in economics.”
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“Obviously, anyone with common sense can see that this plan is a disaster.”
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“The politician’s ‘reform’ is actually just a scheme to line the pockets of his cronies.”
Answer Key
Group 1
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Ambiguity (Does “bat” mean a flying mammal or a piece of sports equipment?)
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Vagueness (What exactly qualifies as “substantial”?)
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Ambiguity (A fire-starter or a romantic partner?)
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Vagueness (What defines a “decent” education is subjective and lacks a clear boundary).
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Ambiguity (Syntactic ambiguity—the structure makes the location of the debt vs. the talk unclear).
Group 2
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Appeal to Tradition (Relying on “how it’s always been done”).
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Ad Hominem (Circumstantial) (Dismissing the argument based on his personal circumstances/lack of a car).
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Poisoning the Well (Attacking the person’s character before they even speak).
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Genetic Fallacy (Judging the theory based on its historical origin/location).
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Appeal to the Masses (Assuming popularity equals truth/effectiveness).
Group 3
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False Cause (Post Hoc) (Assuming A caused B just because A happened first).
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False Dilemma (Presenting two extremes and ignoring middle options).
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Slippery Slope (Predicting a catastrophic chain of events without sufficient evidence).
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Appeal to Ignorance (Assuming truth because it hasn’t been proven false).
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Begging the Question (The conclusion—free speech—is essentially the same as the premise).
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Hasty Generalization (Drawing a universal conclusion about an entire cuisine from one sample).
Group 4
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Euphemism (“Right-sizing” sounds better than “firing”).
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Weaseler (“Possible,” “might,” and “few” water down the claim to avoid responsibility).
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Downplayer (“So-called” minimizes the person’s expertise).
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Proof Surrogate (“Obviously” and “common sense” suggest evidence without actually providing any).
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Dysphemism (“Scheme” and “cronies” produce a negative emotional response compared to neutral terms).
