logic.html

Common Logical Fallacies

Drew Hurley
Santa Fe Community College

SYG 2010
Social Problems

Common Logical Fallacies

Fallacies illustrated in the reading:
Max Shulman's, "Love Is A Fallacy"

Dicto Simpliciter -- An unqualified generalization.

Exercise is good.
Therefore, everyone should exercise.

This is just classroom stuff.
You know the things you learn in school don't have anything to do with real life.
Next Page

Hasty Generalization -- There is too little evidence to support the conclusion.

Examples:

You can't speak French.	We've spent five evenings together.
I can't speak French.	We've gotten along splendidly.
Pete Bellows can't speak French.	It's clear that we are well matched.
Therefore, I conclude that no one at SFCC can speak French.

Post Hoc -- Coincidence is cited as the cause of a phenomena.

Example:

Contradictory Premises -- If the premises of an argument contradict each other there is no argument. Examples:
If God can do anything, can he make a stone so heavy he won't be able to lift it?

What happens when an irresistable force meets an immovable object?

Ad Misercordiam -- A plea of misery asking for pity or sympathy. Examples:

A man applies for a job. When the boss asks what his qualifications are, he replies: 'My wife is a helpless cripple. I've got six children at home. The children have nothing to eat, no clothes to wear, no shoes on their feet, there are no beds in the house, no coal in the cellar, and winter is coming on.'

Or: Polly, I love you! You are the whole world to me, and the moon and the stars and the constellations of outer space. Please, my darling, say that you'll go steady with me, for if you will not, life will be meaningless. I will languish. I will refuse my meals. I will wander the face of the earth, a shambling, hollow-eyed hulk.

False Analogy -- An attempt to equate examples of things that are not equal. For Example: 'Students should be allowed to look at their books during an examination. After all, surgeons have X-rays to guide them during an operation, lawyers have their briefs to help them during a trial, carpenters have blueprints to guide them when they build a house. Why, then shouldn't students be allowed to look at their textbooks during an exam?'

Or: Five dates with you are plenty. After all, you don't have to eat the whole cake to know that its good.

Hypothesis Contrary to Fact -- You cannot begihn an argument with a premise that is not valid and reach any valid conclusion.

Examples: If Madame Curie had not happened to leave a photographic plate in a drawer with a chunk of pitchblende, the world today would not know about radium.

Or: I taught you about fallacies. If I hadn't come along you would have never learned about fallacies.

Poisoning the Well -- Biasing an argument by discrediting the opponent (a form of Ad Hominem fallacy). Examples: Two men are having a debate. The first man gets up and says, 'Ladies and Gentlemen, my opponent is a notorious liar. You can't believe a word he is going to say....'

Or: 'You can't go steady with him, Polly! He's a liar. He's a cheat! He's a Rat!!!'

Other Logical Fallacies

Dramatic Instance -- The tendency to overgeneralize based on a sensational exception to a general pattern. Examples: If one guy can make a success of it, they can all make it!

Or: African-Americans in this country can make just as much as whites. I know a Black businessman who is a millionaire.

Retrospective Determinism -- The claim that things could not have worked out any other way then they did. Examples:
I don't actually know the cause of poverty, but it is here to stay and we must learn to live with it.

Or:
With the election of Lincoln, the Civil War became inevitable.

Misplaced Concreteness -- a statement that attributes real vlaues to an abstraction, using the process of reification. Examples:
Jeep: The best four letter word on wheels.

Society is the cause of all of our social problems.

Ad Hominen -- a personal attack upon an opponent or victim.

Examples: The causes of poverty rest solely on the shoulders of the proverty-stricken people themselves. They have no ambition whatsoever, and it's no one's fault but their own.

Or:
'Bilko is a bombastic southern redneck bigot with a vile tongue and a temper to match. He should be the most despised man in his state....'

Ad Populum -- An appeal to popular prejudices or passions.

Examples: I fight poverty. I work.
What the government does for me is progress; what it does for you is socialism.

Or:
Send all those foreigners and hyphenated-Americans back where they came from.

Circular Reasoning -- Uses conclusions to support assumptions which were necessary to reach these conclusions.

Examples: Blacks are inherently inferior. They are incapable of doing intellectual work, because they are inherently inferior.

Or:
Homosexuals are sex perverts. Homosexuals remain secretive about their sexual preferences because it is a perversion.

Ad Verecundiam -- An appeal to authority to support a claim.

Examples: Trust the President.
The Bible says ....

Or:
Ben Franklin was a remarkable man, and his advice on how to acquire wealth has been heard, at least in part, by millions of Americans throughout history. Moreover, the value of that advice is as equally relevant today as it was for Franklin's contemporaries.

Fallacy of Composition -- The claim that what is valid for a part is also valid for the whole.

Examples: Charles E. Wilson claimed, 'What's good for General Motors is good for the USA!'
Or, Salt is necessary for good health. Therefore, the more salt we eat the healthier we will be.

Or:
When Businesses do well, America succeeds.

Non Sequitur -- Meaning, 'it does not follow.' Facts may be presented which do not acually support the stated conclusions. Examples:

There is the dramatic proof that the amounts of welfare payments made by state governments increased dramatically during the 1980s. Therefore, the number of people unwilling to work for their living increased ....

Or:
In New York City one year, reported assaults were up 200 percent, robberies were up 400 percent, and burglaries were up 1,300 percent. New York experienced a massive crime wave that year!

Send Comments Or Questions To:
drewhurley@claw.org

Credits

Produced at Santa Fe Community College, 1998.

Program Written, Designed and Created by:
Drew Hurley
Santa Fe Community College
3000 NW 83rd Street
Gainesville, FL 32606

ClipArt provided by: Imageline, Inc.
401 East main Street, Suite 100
Richmond, VA 23219

Common Logical Fallacies

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