Logical fallacies
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Logical Fallacies. Errors in judgment and faulty reasoning. Oversimplification. Drastically simple solution to what is clearly a complex problem: We have a balance-of-trade deficit because foreigners make better products than we do. Press here for results. What results???.

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Logical Fallacies

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Logical fallacies

Logical Fallacies

Errors in judgment and faulty reasoning



  • Drastically simple solution to what is clearly a complex problem: We have a balance-of-trade deficit because foreigners make better products than we do.

Press here for results.

What results???

Hasty generalization

Hasty generalization

  • In inductive reasoning, a generalization that is based on too little evidence or on evidence that is not representative: My grandparents eat bran flakes for breakfast, just as most older folks do.

Yes, those are bran flakes.


Post hoc ergo propter hoc

Post hoc, ergo propter hoc

  • “After this, therefore because of this.”

  • Confusing chance or coincidence with causation.

  • The fact that one event comes after another does not necessarily mean that the first event caused the second: I went to the hockey game last night. The next thing I knew I had a cold.

Begging the question

Begging the question

  • Assuming in a premise something that needs to be proven: Lying is wrong because people should always tell the

  • truth.

“Active euthanasia is morally acceptable. It is a decent, ethical thing to help another human being escape suffering through death.”

Premise: It is a decent, ethical thing to help another human being escape suffering through death.

Conclusion: Active euthanasia is morally acceptable.

False analogy

False analogy

  • Making a misleading analogy between logically unconnected ideas: If we can clone mammals, we should be able to find a cure for cancer.

Clone =


Either or thinking

Either/or thinking

  • Seeing only two alternatives when there may in fact be other possibilities: Either you love your job, or you hate it.

Love job!!!

Hate job!!!

Non sequitur

Non sequitur

  • “It does not follow.”

  • An inference or conclusion that is not clearly related to the established premises or evidence: She is very sincere. She must know what she’s talking about.

Very sincere?


Slippery slope a type of non sequitur

Slippery Slope (a type of non sequitur)

  • The speaker argues that, once the first step is undertaken, a second or third step will inevitably follow, much like the way one step on a slippery incline will cause a person to fall and slide all the way to the bottom.

  • “Animal experimentation reduces our respect for life. If we don’t respect life, we are likely to be more and more tolerant of violent acts like war and murder. Soon our society will become a battlefield in which everyone constantly fears for their lives. It will be the end of civilization. To prevent this terrible consequence, we should make animal experimentation illegal right now.”



Loaded language


  • Using words with strongly negative or positive connotations.

  • Example: “The doctor’s horse-and-buggy attitudes tyrannize mothers.”

Bandwagon appeal


  • Urging readers to adopt a course of action because “everyone is doing it”.

  • “Every other high school in the county has a soccer team; we need one, too.”

Monkey see, monkey do.

Circular reasoning


  • Supporting a point by merely stating it in other words.

  • Example: “The law should be amended because it needs changing.”

Change the law

Should be amended

Ad hominem

Ad hominem

  • In an ad hominem argument, the arguer attacks his or her opponent instead of the opponent’s argument.

“Andrea Dworkin has written several books arguing that pornography harms women. But Dworkin is just ugly and bitter, so why should we listen to her?”

What??? Ugly and bitter, so what?

Red herring

Red Herring

  • Partway through an argument, the arguer goes off on a tangent, raising a side issue that distracts the audience from what’s really at stake. Often, the arguer never returns to the original issue.

  • “Grading this exam on a curve would be the most fair thing to do. After all, classes go more smoothly when the students and the professor are getting along well.”

Helping people get along doesn’t necessarily make it more fair

No evidence as to why a curve would be fair.

Straw man argument a subtype of the red herring

Straw Man Argument: A subtype of the red herring

  • In the straw man fallacy, the arguer sets up a weak version of the opponent’s position and tries to score points by knocking it down. But just as being able to knock down a straw man (like a scarecrow) isn’t very impressive. Includes any lame attempt to "prove" an argument by overstating, exaggerating, or over-simplifying the arguments of the opposing side.

  • The opponent argues, "Tennessee should increase funding to unemployed single mothers during the first year after childbirth because they need sufficient money to provide medical care for their newborn children." The second speaker retorts, "My opponent believes that some parasites who don't work should get a free ride from the tax money of hard-working honest citizens. I'll show you why he's wrong . . ."

Weak opponent created=

Straw man

Just a few of the many

Just a few of the many

  • Logical

  • Fallacies

The End

for now. . .

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