Skip to main content
Logical Fallacies

Informal Logical Fallacies

intermediate6 min readpolitics · education · logic · philosophy · psychology

A set of 17 scenarios each committing an informal logical fallacy, used for practice in identifying fallacies.

THE IDEA

Practice: informal logical fallacies

In the following exercise, you will practice identifying informal logical fallacies. To prepare, it is helpful to review what informal fallacies are, how they are classified, and why developing the skill to spot them matters.

A logical fallacy is an argument that contains faulty reasoning. Formal fallacies occur when the structure of an argument is invalid, whereas informal fallacies arise from errors in the content of the argument. This guide is concerned entirely with informal logical fallacies.

Informal fallacies can be grouped into five broad categories:

  1. Linguistic fallacies – Arguments weakened by vague or ambiguous language.
  2. Fallacies of omission – Arguments that leave out vital information or misrepresent alternatives to steer the listener toward a particular conclusion.
  3. Fallacies of intrusion – Arguments that incorporate irrelevant material, such as appeals to fear or pity, in place of genuine evidence.
  4. Fallacies involving built‑in assumptions – Arguments that rely unquestioningly on presumptions about tradition, nature, or other people.
  5. Causal fallacies – Arguments based on a misunderstanding of cause and effect, such as assuming that sequential events are causally related.

For each argument, explain which premise or inference is weak and why. A fallacy label is useful only if you can show how the reasoning fails; more than one diagnosis may fit.

Identify and explain the reasoning errors in the following examples.

  1. Marriage is just natural. It is a fundamental component of human life and it springs from human nature. To oppose marriage is to oppose human nature.

  2. Plato was one of the first great philosophers. Plato taught that democracy was inherently flawed. It follows then, that all philosophers are opposed to democracy, and one should be cautious when reading their works.

  3. The day after I broke up with my girlfriend, my car would not start. I am sure that she sabotaged my car engine.

  4. Why am I supporting candidate Mulhauser for governor? Because Chuck Norris supports him! Chuck Norris is a very successful actor and he must know what he is talking about.

  5. My dog is so much smarter than your cat. Ignorance is written all over your cat’s face.

  6. Seventy-three percent of all those surveyed outside the Bentonville Thrift-Mart opposed abortion. Therefore, it is safe to say that the majority of Americans oppose abortion.

  7. I ate breakfast at the Greasy Spoon two years ago. The coffee was terrible. The Greasy Spoon is an awful restaurant.

  8. Are you a college student or are you a drop-out?

  9. Our new president is secretly a Socialist. How do I know this? Because my uncle Ricardo told me and my uncle is an honest man.

  10. Boss: I need the report by Tuesday. Employee: Why do you need it by Tuesday? Boss: Because if I don’t have it on Tuesday, you’ll be out of work on Wednesday!

  11. Christians say that God is love. Love is an emotion. So, God is simply an emotion.

  12. Ken argues that the Iraq War is morally wrong. But, Ken is just bitter because his wife left him. He is just being emotional.

  13. Keith: War is always caused by intolerant religious fanatics. Owen: Really? What about the Civil War, World War I, World War II, the Korean War, and the Vietnam War? Keith: Exactly! You have proven my point.

  14. After the young man read Richard Dawkins’ book The God Delusion, he took his own life. It is clear that Dawkins’ book caused the man to commit suicide. Furthermore, Dawkins should be held responsible for the young man’s death.

  15. The Founding Fathers argued that all people are created equal. This is clearly untrue. Some people are better athletes than others; some are more intelligent than others. So, the Founding Fathers must have been wrong.

  16. Either God created the world as stated in the book of Genesis, or life is a product of random chance. Both options cannot be true. If God created the world, then the Bible is true. If God did not create the world, then life is meaningless.

  17. Bumper sticker: You can either save the trees or use plastic toilet paper!

When to use it

  • Evaluating arguments in political speeches to identify misleading tactics.

  • Analyzing advertisements for logical flaws that exploit emotions or omit information.

  • Improving your own argumentation by avoiding common informal fallacies.

  • Teaching critical thinking skills by illustrating how fallacies undermine reasoning.

  • Debating a controversial topic with friends or colleagues to ensure arguments remain logical and constructive.

  • Analyzing political speeches and campaign advertisements to identify manipulative tactics.

  • Critically reading news articles or opinion pieces to separate factual reasoning from emotional appeals.

  • Evaluating arguments in academic papers or business proposals for logical soundness.

  • Debating political issues

  • Evaluating advertisements

  • Analyzing news articles

  • Improving personal reasoning

FROM THEORY TO EVERYDAY LIFE

In practice

01

Linguistic Fallacy: The 'Everyone is entitled to their opinion' argument

Using vague phrases like 'everyone is entitled to their opinion' to shut down debate, without clarifying whether all opinions are equally valid or well-supported.

02

Fallacy of Omission: Cherry-picking data

A politician presents only crime statistics from one year to argue that crime is decreasing, ignoring data from other years that show an upward trend.

03

Ad Hominem in a Political Debate

During a debate, a candidate attacks their opponent’s character instead of examining a tax proposal: 'You can't trust his tax plan because he was once convicted for tax evasion.' That history may bear on the person’s credibility, but it does not by itself show that the proposal’s calculations or policy claims are wrong.

04

Straw Man in a Classroom Discussion

A student argues that we should reduce homework to improve mental health. Another student responds, 'So you want to abolish all homework and let students do nothing?' This misrepresentation is a straw man fallacy that makes the original argument easier to attack.

05

Appeal to Nature

  1. Marriage is just natural. It is a fundamental component of human life and it springs from human nature. To oppose marriage is to oppose human nature.
06

Hasty Generalization

  1. Plato was one of the first great philosophers. Plato taught that democracy was inherently flawed. It follows then, that all philosophers are opposed to democracy, and one should be cautious when reading their works.
07

Post Hoc Ergo Propter Hoc

  1. The day after I broke up with my girlfriend, my car would not start. I am sure that she sabotaged my car engine.
08

Appeal to Authority

  1. Why am I supporting candidate Mulhauser for governor? Because Chuck Norris supports him! Chuck Norris is a very successful actor and he must know what he is talking about.
09

Unsupported Insult

  1. My dog is so much smarter than your cat. Ignorance is written all over your cat’s face. The insult supplies no evidence for the comparison. Since the cat is not presenting an argument, this is not a straightforward case of attacking an arguer instead of answering their reasoning.
010

Hasty Generalization (Biased Sample)

  1. Seventy-three percent of all those surveyed outside the Bentonville Thrift-Mart opposed abortion. Therefore, it is safe to say that the majority of Americans oppose abortion.
011

Faulty Generalization

  1. I ate breakfast at the Greasy Spoon two years ago. The coffee was terrible. The Greasy Spoon is an awful restaurant.
012

False Dilemma

  1. Are you a college student or are you a drop-out?
013

Appeal to False Authority

  1. Our new president is secretly a Socialist. How do I know this? Because my uncle Ricardo told me and my uncle is an honest man.
014

Appeal to Force (Argumentum ad Baculum)

  1. Boss: I need the report by Tuesday.

Employee: Why do you need it by Tuesday?

Boss: Because if I don’t have it on Tuesday, you’ll be out of work on Wednesday!

015

Equivocation

  1. Christians say that God is love. Love is an emotion. So, God is simply an emotion.
016

Ad Hominem (Circumstantial)

  1. Ken argues that the Iraq War is morally wrong. But, Ken is just bitter because his wife left him. He is just being emotional.
017

Hasty Generalization / Confirmation Bias

  1. Keith: War is always caused by intolerant religious fanatics.

Owen: Really? What about the Civil War, World War I, World War II, the Korean War, and the Vietnam War?

Keith: Exactly! You have proven my point.

018

Straw Man / Equivocation About Equality

  1. The Founding Fathers argued that all people are created equal. This is clearly untrue. Some people are better athletes than others; some are more intelligent than others. So, the Founding Fathers must have been wrong.
✳

A MOMENT TO REFLECT

Put it to work.

  1. Can you identify an informal fallacy in a recent news article or political speech?

  2. How might a linguistic fallacy cause confusion in a debate about a controversial topic?

  3. Why is it important to distinguish between formal and informal fallacies when analyzing arguments?

  4. Choose a disputed argument. Which premise or inference would you challenge, and can you explain the problem without naming a fallacy?

  5. Recall a time when you realized someone was using a fallacy against you. How did you respond, and how might studying fallacies help you handle similar situations in the future?

  6. How can the skill of detecting fallacies improve your decision-making in everyday life, such as when evaluating product claims or political promises?

  7. Which of these fallacies do you encounter most often in everyday arguments?

  8. How would you refute an argument that uses a false dilemma?

  9. Why is it important to distinguish between correlation and causation?

Often confused with

Informal Logical Fallacies↗

CONTINUE THE CONVERSATION

Source texts

  • Informal Logical Fallacies A Brief Guide
  • Informal Logical Fallacies A Brief Guide
  • Informal Logical Fallacies A Brief Guide
EXPLORE FURTHER
← More logical fallacies