Informal Fallacies

Introduction to Logic

"It is the business of one who knows a thing, himself to avoid fallacies in the subjects which he knows and to be able to show up the man who makes them; and of these accomplishments the one depends on the faculty to render an answer, and the other upon the securing of one."

Aristotle, Sophistical Refutations, 1 (165a .20)

Fallacies of Relevance

Appeal to Force

"I think you'll agree," said the lobbyist to the congressman, "that the legislation I'm promoting is sound when you consider the number of your constituents I represent."
At the Yalta Peace Conference at the end of WWII, when Churchill said that the Pope had suggested a certain course of action, Stalin asked, "And how many divisions did you say the Pope had available for combat duty?"

Argumentum ad hominem (Abusive)

Whatever he says, don't you believe it. He's one of those ignorant southerners.
Student: "But teacher, my father told me this book was a good source for my history paper."
Teacher: "Was your father a history major?"
Michael Dukakis is a member of the ACLU.

Argumentum ad hominem (Circumstantial)

When a hunter was criticized for killing harmless animals for amusement, the hunter replied, "Don't you feed on the flesh of harmless cattle?"
"Listen, preacher," said the thief as he took the pastor's wallet, "you ought to let me have your money because the Bible says to do good to them which despitefully use you."

Argument from Ignorance

There must be ghosts because no one has ever been able to prove they don't exist.
"Of course you are a spy," declared the officer, "because no one has proven your loyalty."

Appeal to Pity

Please officer, if you give me a ticket my insurance rate will go up and then I won't be able to pay my wife's hospital bills and my three kids will starve.

Argumentum ad populum (snob-appeal; band-wagon)

He was a simple man who held the virtues that we all esteem--honesty, hard work, a simple life. But then these brutes forced him to give over his land without any reason!
"Mom, mom, mom!" the boy called out. "I have to get these sneaker's because they're Air Jordans!"

Appeal to Authority

Not always a fallacy. Authority must be recognized and established beforehand, and must be an authority in the area at hand.
Many scientists are atheists; therefore, atheism must be scientific.
Harlow Shapley, considered the "Dean of American astronomers," was considered by many journalists to be an authority on every subject.

Accident

Fallacies of accident "occur whenever any attribute is claimed to belong in like manner to a thing and to its accident. For since the same thing has many accidents there is no necessity that all the same attributes should belong to all of a thing's predicates and to their subject as well." (Sophistical Refutations, 5 (166b.30))
"There is no fallacy more insidious than that of treating a statement which in many connections is not misleading as if it were true always and without qualification." (H.W.B. Joseph, An Introduction to Logic quoted in Copi, 96)
"Well said, Cephalus, I replied; but as concerning justice, what is it?--to speak the truth and to pay your debts--no more than this? And even to this are there not exceptions? Suppose that a friend when in his right mind has deposited arms with me and he asks for them when he is not in his right mind, ought I to give them back to him? No one would say that I ought or that I should be right in doing so, any more than they would say that I ought always to speak the truth to one who is in his condition." (Plato, Republic, Book I)
What you bought yesterday, you eat today. You bought raw meat yesterday, so you eat raw meat today.
If Coriscus be different from "man", he is different from himself: for he is a man.
If he be different from Socrates, and Socrates be a man, then he has admitted that Coriscus is different from a man, because it so happens (accidit) that the person from whom he said that he (Coriscus) is different is a man.

Converse Accident or Hasty Generalization

All the swans in this pond are white; therefore, all swans are white.
"Whoa, dude! If this pot can help people with glaucoma and stuff, then everybody should be able to have it."

False Cause, post hoc ergo propter hoc, "after this, therefore because of it"

"The refutation which depends upon the consequent arises because people suppose that the relation of consequence is convertible. For whenever, suppose A is, B necessarily is, they then suppose also that if B is, A necessarily is. This is also the source of the deceptions that attend opinions based on sense-perception.
For people often suppose bile to be honey because honey is attended by a yellow colour: also, since after rain the ground is wet in consequence, we suppose that if the ground is wet, it has been raining; whereas that does not necessarily follow.
In rhetoric proofs from signs are based on consequences. For when rhetoricians wish to show that a man is an adulterer, they take hold of some consequence of an adulterous life, viz. that the man is smartly dressed, or that he is observed to wander about at night. There are, however, many people of whom these things are true, while the charge in question is untrue." (Sophistical Refutations, 5 (167b.0))
"Wow," said one native to another. "Every time I beat the drums after an eclipse, the sun reappears. The sun obeys my beat!"

Begging the Question

"Those that depend on the assumption of the original point to be proved, occur in the same way, and in as many ways, as it is possible to beg the original point; they appear to refute because men lack the power to keep their eyes at once upon what is the same and what is different." (Sophistical Refutations, 5 (176a.35))
Shakespeare is a greater writer than Robbins because people with good taste in literature prefer Shakespeare. A person with good taste in literature is one who prefers Shakespeare to Robbins.
All swans are white.
Wait, here is a black one.
That's no swan; it's the wrong color.

Complex Question

"Those that depend upon the making of two questions into one occur whenever the plurality is undetected and a single answer is returned as if to a single question." (Sophistical Refutations, 5 (168a.0))
Does the earth consist of sea, or the sky?
When did you stop beating your wife?
Where did you hide the evidence?
Why is private development of resources so much more efficient than private control?
Have all criticisms noted in the exam report been addressed by the Board of Directors? If no, please provide details. [actual bank deposit insurance renewal form]

Irrelevant Conclusion, non sequitur, "it does not follow"

"Arguments of that kind, then, though not inconclusive absolutely, are inconclusive in relation to the proposed conclusion. Also even the questioners themselves often fail quite as much to see a point of that kind." (Sophistical Refutations, 5 (167b.25))
Ladies and gentleman of the jury, this man is accused of murder, and we all know that murder is a horrible crime. It violates our most basic right. It cuts off opportunities for everyone whose life it touches. Keep that in mind as you decide on this case.
Vegetables, in the proper combinations, can provide all of the nutrients necessary for human life. A mixture of whole grains and legumes, for instance, contains protein of a quality at least as high as that of animal protein, and the major vitamin and mineral groups can easily be represented in an all-vegetable diet. What's more, a little culinary imagination can make a vegetarian feast as varied and interesting as any meal based around meat. Given these facts, it's certainly time that we outlaw the raising and slaughtering of domestic livestock and turn to the wider cultivation of high-nutrition crops.

Red Herring

In the thick tension of the disciplinary interview the employee quipped, "So how 'bout them Indians?"
When asked if he condoned receiving campaign donations from Communist Chinese officials, President Clinton answered, "I have been very vocal in my support for campaign finance reform."
The senator, about to be arraigned on fraud charges, said, "The judicial system in this country is in need of major reforms."

Tu Quoque; "You too!"

"Well wife," frowned the husband, "I may not take out the garbage, but you never clean up the kitchen!"

Straw Man

Setting up an overly simplistic caricature of your opponent's argument and then knocking it down.
Liberals support the United Nations. Clearly, therefore, liberals believe want to surrender our national sovereignty.

Special Pleading

Look, Mussolini got the trains to run on time and the Italian people were happy.

Argument of the Beard

Setting up an arbitrary limit and then forcing it to be defended.
How many people make a crowd, Mr. Smith?
I would say seven.
Were there seven people at the party the night your wife was murdered?
Yes, I believe so.
Then there was a crowd there and you could have been lost in the crowd while you sneaked out and killed your wife, couldn't you?

Slippery Slope

All it takes is one communist in America and soon there will be a hammer and sickle flying above the Capitol.

False Dichotomy or Dilemma

Either you support my campaign or your are willing to sell us out to our enemies.

Faulty Analogy

Electricity is like water flowing through pipes; therefore, electricity will leak out of the wall unless you stop it up.

Fallacies of Ambiguity

Equivocation

The end of a thing is its perfection; death is the end of life; hence, death is the perfection of life.
Some dogs have floppy ears; my dog has floppy ears; therefore, my dog is some dog.
Those learn who know: for it is those who know their letters who learn the letters dictated to them.
Evils are good: for what needs to be is good, and evils must needs be.
The same man is both seated and standing and he is both sick and in health: for it is he who stood up who is standing, and he who is recovering who is in health: but it is the seated man who stood up, and the sick man who was recovering.

Amphiboly

Toscanini's son did not know how to conduct himself.
If Croesus went to war with Cyrus, he would destroy a mighty kingdom.
I wish that you the enemy may capture.
There must be knowledge of what one knows:
There must be sight of what one sees: one sees the pillar: ergo the pillar has sight
What you profess to-be, that you profess to-be: you profess a stone to-be: ergo you profess-to-be a stone.
Speaking of the silent is possible.

Accent

Revolution in France
feared by authorities
We should not speak ill of our friends. (So is it acceptable to speak ill of our enemies?)

Composition

a.
Since each ship in the fleet is ready for battle, the whole fleet must be ready.
Since every part in this machine is light, the whole machine must be light.
b.
Since a bus uses more gasoline than a car, all buses must use more gasoline than all cars.
Since an atomic bomb can do more damage than a conventional bomb, all atomic bombs must have done more damage than all conventional bombs.

Division

I made thee a slave once a free man.
God-like Achilles left fifty a hundred men.
Since this machine is heavy, each of its parts must be heavy.
American Indians are disappearing; that man is an American Indian; therefore, that man is disappearing.

Answers to Fallacy Examples

pp. 101-110

1. Arg from ig/ir. concl?

2. Accident?

3. Begging the Question

4. Ad homimen circ.

5. Ad populum

6. Appeal to Authority

7. Irrelevant conc.

8. Argument from ignorance?

9. False cause

10. Irrelevant conc.

11. Begging the Question

12. Ad hominem abusive

13. Ad homimen abusive

14. Irrelevant conc.

15. Appeal to force

16. Begging the Question

17. Ad populum

18. Argument from ignorance

19. Appeal to force-not a fallacy in this case

20. False cause

21. Ad homimen abusive

22. Ad populum

23. Argument from ignorance

24. Complex Question

25. Irrelevant conc.

26. Accident

27. Appeal to force

28. Argument from ignorance

29. Appeal to pity

30. Irrelevant conc.

31. Ad homimen circ/abusive

32. Complex Question

33. Hasty gen & accident

34. False cause

35. Ad homimen ab/circ.

36. Ad homimen ab/circ.

37. Irrelevant conc.

38. False cause

39. Appeal to force

40. Begging the Question

41. Appeal to pity

42. Irrelevant conc.

43. Hasty generalization

44. Ad homimen abusive

45. Appeal to authority

46. Argument from ignorance

47. Ad homimen abusive

48. Ad homimen circ.

49. Appeal to force

50. False cause

pp. 117-118

1. Composition

2. Equivocation

3. Equivocation

4. Composition

5. Accent

6. Amphiboly

7. Composition

8. Equivocation

9. Equivocation

10. Composition

11. Equivocation

12. Division

13. Composition

14. Equivocation

15. Composition

16. Division

17. Accent

18. Equivocation

19. Equivocation

20. Division

21. Amphiboly

Search this site and more

This page was last modified on Thursday, January 16, 2003.
You may contact the instructor at SHKaminski@yahoo.com
This material is for the exclusive use of the students in classes taught by Steven H. Kaminski. Unauthorized use is prohibited.