Philosophy
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Fallacies-2.pptx1
Logical Fallacies: Errors in Reasoning
Argument: In logic and philosophy, an argument is a series of statements typically used to persuade someone of something or to present reasons for accepting a conclusion. The general form of an argument in a natural language is that of premises (typically in the form of propositions, statements or sentences) in support of a claim: the conclusion.
Logical Fallacies
Arguments are the tools of philosophers. They are what philosophers use to support their positions and to persuade one another to their point of view. Be careful of arguments that contain fallacies, however, which are errors in reasoning. The overall cogency of an argument could be affected, if it contains a logical fallacy. The fallacies in this Power Point are not meant to constitute an exhaustive list, but they are some of the more prominent ones.
Logical Fallacies
Type 1 Reasoning Error: Believing a falsehood (false positive; believing something is real when it is not).
Type 2 Reasoning Error: Rejecting a truth (false negative; not believing something is real when it is).
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Two Major Groups of Fallacies
I. Fallacies in Supporting a Claim.
II. Fallacies of Criticism and Response.
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I. Fallacies in Supporting a Claim
Four Fallacies of Relevance
Fallacies in this group involve premises not relevant to the conclusions they are meant to support.
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I. Fallacies in Supporting a Claim
Appeal to Ignorance
(Ad Ignorantiam)
The appeal to ignorance consists in arguing that because a claim has not been demonstrated to be wrong, the claim is right.
Appeal to Ignorance
Claim: “God exists.”
Claimant has the burden of proof or production to put forth reasons, evidence, or arguments in support of that claim.
Fallacy: “Can you prove to me that God does not exist?”
Also known as “shifting the burden of proof.”
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I. Fallacies in Supporting a Claim
“Of course I believe in telekinesis. No one has ever shown it does not exist, and that’s good enough for me.”
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I. Fallacies in Supporting a Claim
Extraordinary claims require extraordinary evidence. The claimant has the burden of proof.
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I. Fallacies in Supporting a Claim
The legislature has passed a law requiring public school teachers to swear an oath of loyalty to the United States. The House Speaker summed up the thinking of the legislature. ‘”There didn’t seem to be any reason we shouldn’t have such a law,” he said. “No one showed us anything wrong with it, so we concluded it was all right.”
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I. Fallacies in Supporting a Claim
The fallacy is also committed in arguing that because a claim has not been demonstrated to be correct, it is wrong.
“No one has ever proved that decriminalizing drug possession is socially desirable. So it isn’t desirable.”
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I. Fallacies in Supporting a Claim
Appeal to Inappropriate Authority (Ad Verecundiam)
We base much of what we believe on the evidence of authority, and citing an authority is a legitimate way of justifying a belief.
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I. Fallacies in Supporting a Claim
A fallacy, however, is committed when the authority cited is not an authority in the proper area. The expertise of the authority is thus irrelevant to the claim and provides no support for it.
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Example: Einstein’s expertise lies in physics--not religion, politics, or gardening.
In 1921 a rabbi sent Albert Einstein a telegram with the question: “Do you believe in God?”
Einstein’s response: “I believe in Spinoza’s God, who reveals himself in the orderly harmony of what exists, not in a God who concerns himself with the fate and the doings of mankind.”
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I. Fallacies in Supporting a Claim
Hard Experts
Mathematics
Physics
Chemistry
Soft Experts
Art
Politics
Religion
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I. Fallacies in Supporting a Claim
Appeal to Popular Belief (Popularity of a Belief)
(Ad Populum)
This fallacy consists in asserting that a claim is correct just because people generally believe it is. Such an inference is in error because we have no reason to take what most people believe as a reliable indicator of what is true.
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Examples of the Popularity or Unpopularity of Beliefs
“Everyone believes in X.”
“No one believes in X.”
Why is that?
What arguments, reasons, or evidence can the claimant put forth in support of X?
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I. Fallacies in Supporting a Claim
Appeal to Popular Attitudes (Emotions)
(Ad Populum)
Popular attitudes and the emotions associated with them can be manipulated to incline people to accept claims that have not been demonstrated.
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I. Fallacies in Supporting a Claim
Racial fears and prejudices, patriotic impulses, and the wish to be associated with a special social group are some sources of such sentiments and attitudes.
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I. Fallacies in Supporting a Claim
“I’ll tell you why I still believe we were right to fight in Iraq. It’s because I love my country.”
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I. Fallacies in Supporting a Claim
“Now look, Sally. You know that Communism isn’t right. What would your friends at school think if they heard you talking this way?”
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I. Fallacies in Supporting a Claim
Two Fallacies of Inadequate Evidence
Fallacies in this group are arguments with premises that present relevant, but inadequate, evidence.
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I. Fallacies in Supporting a Claim
False Cause (Post Hoc)
This fallacy involves concluding that because one event occurred before another, the first was the cause of the second.
Causation?
Correlation?
Coincidence?
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Example of False Cause
“Everytime I wash my car, it rains the following day. Therefore, washing my car caused the rain to come down.”
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Example of False Cause
A few minutes after the coach of the Houston Texans made his speech to the City of London, a devastating explosion occurred. For the safety of the people who live and work in the City, it is imperative that the coach makes no more speeches here.
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I. Fallacies in Supporting a Claim
“Ever since mayor Smith took office, the economy went south. Therefore, Smith caused our economy to go down.”
Wearing favorite shirt ⇒ Your team wins
Viewing violent TV shows ⇒ Violent behavior in children
Pornography ⇒ Rape
“Hope you getting a speeding ticket.” (In jest) ⇒ Your friend gets a speeding ticket.
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I. Fallacies in Supporting a Claim
Hasty Generalization
This fallacy consists in generalizing on the basis of an inadequate set of cases.
Also called insufficient sample, faulty generalization, or biased generalization.
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I. Fallacies in Supporting a Claim
“All politicians are dishonest.”
“All people on welfare are lazy.”
“All lawyers are greedy.”
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I. Fallacies in Supporting a Claim
Four Fallacies of Illegitimate Assumption
Fallacies in this group are tied together by the fact that each invokes some illegitimate assumption.
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I. Fallacies in Supporting a Claim
False Alternatives
The fallacy consists in giving arguments that present alternatives as exhaustive and exclusive when they are not. False alternatives are used to make us choose between restricted alternatives when other choices really exist.
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I. Fallacies in Supporting a Claim
“Either you’re for us or you’re against us. It is obvious you aren’t for us. So you’re against us.”
Neutral?
No knowledge of the issues?
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I. Fallacies in Supporting a Claim
“Either we cut spending or increase the deficit.”
Raising taxes?
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I. Fallacies in Supporting a Claim
“Either we have much more capital punishment or keep putting murderers back out on the street.”
Mandatory life imprisonment?
Rehabilitation?
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I. Fallacies in Supporting a Claim
Loaded Question (Complex Question)
This fallacy consists in attempting to get an answer to a question that assumes the truth of an unproved assumption.
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I. Fallacies in Supporting a Claim
“So how many times did you beat your wife today?”
“Mr. President. How long will you continue to lie to the American people?”
“Are you lying now or were you lying then?”
“Did you see the gun?”
“Did you see a gun?”
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I. Fallacies in Supporting a Claim
Begging the Question (Petitio Principii)
A “question” is an issue, and a question is “begged” when reasons justifying an answer to it are only apparently presented in an argument.
You assume the very thing that you’re asked to prove.
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I. Fallacies in Supporting a Claim
“Paranormal phenomena exist because I have had experiences that can only be described as paranormal.”
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I. Fallacies in Supporting a Claim
Person A: The Big Mac is the tastiest burger in the world.
Person B: Why do you say that?
Person A: Just because.
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I. Fallacies in Supporting a Claim
The conclusion restates part or all of the meaning of a premise.
“Freddie is a murderer because Freddie wrongfully killed someone.”
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I. Fallacies in Supporting a Claim
A premise is used to support a conclusion while the conclusion is at least implicitly appealed to in support of the premise (also called circular reasoning.)
A because B, B because C, C because A.
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Example of Circular Reasoning
Three thieves pull off a successful heist and steal four diamonds, but they can’t decide how to divide their haul. Eventually the first thief says: “I should get two diamonds, and you two should get one each, because I’m the leader.” The second thief says: “Wait a minute, why are you the leader?” The first thief replies: “I must be the leader; I’m getting the largest share of the haul!”
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I. Fallacies in Supporting a Claim
Slippery Slope
The mistaken idea behind this fallacy is that when actions can be arrayed along a continuum, justifying the first action is equivalent to justifying the most extreme ones.
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I. Fallacies in Supporting a Claim
“Our employees have asked us to provide lounge areas where they can spend their breaks. This request will have to be refused. If we give them lounge areas, next they’ll be asking for a swimming pool and sauna. Then it will be tennis courts, football fields, and a fitness center.”
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II. Fallacies of Criticism and Response
Four Fallacies of Criticism
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II. Fallacies of Criticism and Response
Against the Person (Ad Hominem)
The fallacy consists in rejecting the claim by offering as grounds some personal characteristics of the person supporting it.
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II. Fallacies of Criticism and Response
“You should not accept Dr. Smith’s proposed cure for cancer, because she is an active member of the Communist Party.”
But compare: “Dr. Smith says that businesses and companies should be privately owned by individual citizens, and that the government should not try to regulate them. However, Dr. Smith is a communist.”
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II. Fallacies of Criticism and Response
Exception to
Against the Person fallacy:
We may legitimately question the reliability of a person in a particular set of circumstances (and hence, we would not be committing this fallacy) such as conflict of interest, vested interest, etc.
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II. Fallacies of Criticism and Response
A chemical company’s representative assuring us the company’s pesticide is harmless.
A manufacturer claiming her product is safe to use.
A bureaucrat asserting his department is underfunded.
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II. Fallacies of Criticism and Response
Pooh-Pooh
To pooh-pooh an argument is to dismiss it with ridicule as not worthy of serious consideration. It is a refusal to examine an argument seriously and evaluate it fairly.
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II. Fallacies of Criticism and Response
“We don’t have to waste time dealing with Mr. Johnson’s claim about the elections being rigged. He’s just a sore loser.”
Logging company’s response to environmental group’s insistence that the world’s tallest tree not be chopped down.
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II. Fallacies of Criticism and Response
Straw Man
The fallacy consists in misrepresenting an opponent’s claim or argument so that it is easier to criticize or so obviously implausible that no criticism is needed.
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II. Fallacies of Criticism and Response
“The theory of evolution boils down to the idea that human beings are descended from apes.”
This statement presents no theory that any serious scientist holds.
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II. Fallacies of Criticism and Response
Name Calling (Loaded Words)
When we apply judgmental words like sleazeball, incompetent, idiot, morally corrupt, venal, avaricious, and decadent to people, policies, or practices, we must justify the application.
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Two Fallacies of Defense
Definitional Dodge
This fallacy consists in redefining a crucial term in a claim to avoid acknowledging a counterexample that would falsify a claim.
Definitional Dodge
All men are mortal.
Suzy is not a man.
Therefore, Suzy is not mortal.
“Doctors recommend that you should start your day with a good breakfast. I had a very good breakfast this morning when I ate bacon, fried eggs, and pancakes.
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Two Fallacies of Defense
The Exception that Proves the Rule
Someone defending a claim commits this fallacy by dismissing apparent counterexamples as no challenge (or hand waves those challenges away).
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Exception that Proves the Rule
Homer: “All animated series are short-lived. They don’t last very long.”
Marge: “But aren’t you forgetting long-running shows like The Simpsons and South Park?”
Homer: “But those are just exceptions that prove the rule.”
Exception that Proves the Rule
Of course, Homer could argue back and say that the counterexamples given by Marge are not compelling counterarguments and do not really contradict his initial statement. In this case, however, it may be hard for him to make this argument, since these are two long-running shows.
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Last Words
Errors in reasoning are always difficult to avoid and often hard to detect. Knowing the names of a few prominent kinds of fallacies may be helpful, but it is no substitute for constant vigilance and ready skepticism.
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Bibliography
The information in these slides come from The Elements of Reasoning, by David Conway and Ronald Munson.
