Logical Fallacies

What is a logical fallacy?

A logical fallacy is an error in logic that can make a plausible, but misleading argument.

Inductive fallacies: Inductive fallacies are the result of the incorrect use of evidence.Ex: “This chalk is white; therefore, all chalk is white.”*With inductive fallacies, an arguer leaps to a conclusion based on insufficient

evidence*

Deductive fallacies: Deductive fallacies are the result of a failure to follow the logic of a series of

statements.Ex: “The rooster crows at 5:00 AM, and the sun rises at 5:00 AM; therefore the

rooster makes the sun rise.”*With inductive fallacies, an arguer makes an incorrect or unsupported link

between cause and effect*

Logical Fallacies (cont.)

While there are two main categories of logical fallacies, it is important to note that there is often overlap.

Some fallacies may fit into both categories.

However, it is important to note that logical fallacies occur when :a)An arguer incorrectly links cause and effect.b)An arguer leaps to a conclusion based on insufficient evidence.

Logical Fallacies (cont.)

#1.) HASTY GENERALIZATION:Prematurely jumping to a presumptuous conclusion.Prejudices and superstitions are the result of making a hasty generalization.Ex: “There was a news story about a guy in a fraternity who was a rapist, so

now I carry mace if I know I’ll be going anywhere near a frat house.”How is this an example of the Hasty Generalization logical fallacy?It’s a prejudiced point of view. The arguer assumes that because one person

in a fraternity is a rapist, all people in fraternities are rapist. The arguer is jumping to a presumptuous conclusion about people in fraternities.

Logical Fallacies (cont.)

#1.) HASTY GENERALIZATION (cont.):Ex: “Last time I walked past a black cat, I tripped and hurt my arm, so now I

avoid black cats altogether.”How is this an example of the Hasty Generalization logical fallacy?It is a superstitious belief. The arguer is assuming that the cat caused her to

initially injure herself, so now she extends that fear to all cats. She is jumping to a presumptuous conclusion about cats.

Logical Fallacies (cont.)

#2.) FAULTY USE OF AUTHORITY:Falsely recognizing someone as an authority on something.Accepting someone’s credentials without careful evaluation.EX:http://www.youtube.com/watch?v=bZIzRqDOSZohttp://www.youtube.com/watch?v=dgdYbHvXuVAhttp://www.youtube.com/watch?v=IRPHHAIAtks

How are these commercials examples of the Faulty Use of Authority logical fallacy?

Each commercial assumes a connection between the specific celebrity’s popularity and their authority on the product or service they are promoting.

Logical Fallacies (cont.)

#3.) POST HOC or DOUBTFUL CAUSE:Assuming that because one event follows another, the first event is the cause

of the second.Ex: “The rooster crows at 5:00 AM, and the sun rises at 5:00 AM; therefore

the rooster makes the sun rise.”How is this an example of the Post Hoc logical fallacy?The arguer assumes that simply because these two events occur sequentially,

there is a cause and effect relationship between them.

Logical Fallacies (cont.)

#3.) POST HOC or DOUBTFUL CAUSE (cont.):Ex: “A tornado hit my town after a group of Satan worshippers moved in, so

god sent the tornado to punish us for allowing them to move here.”How is this an example of the Post Hoc logical fallacy?The arguer assumes a connection between the Satan worshippers and the

tornado.

Logical Fallacies (cont.)

#4.) FALSE ANALOGY: Drawing an analogy or comparison between two situations that are totally

dissimilar.Ex: “We know that overweight people have a higher mortality rate than thin

people. We also know that black people have a higher mortality rate than white people. Do we subject black people to torturous treatments to bleach their skin? Of course not. We have enough sense to know that skin-bleaching will not eliminate sickle-cell anemia. So why do we have blind faith that weight loss will cure the diseases associated with obesity?”

-Susan Wooley, Director of eating disorders clinic at The University of Cincinnati.

How is this an example of the False Analogy logical fallacy?The arguer assumes that skin color and weight are analogous. She assumes that

diseases that are specific to people of a certain skin color can be treated just like diseases that are specific to people of a certain weight.

Logical Fallacies (cont.)

#5.) AD HOMINEM: Attacking a person’s character rather than their statements.Latin for “against the man.”Ex: “Ernest Hemingway was an alcoholic and a terrible father, so I won’t read

his books.”How is this an example of the Ad Hominem logical fallacy?The arguer is attacking Ernest Hemingway’s character rather than his

intellectual output.

Logical Fallacies (cont.)

#5.) AD HOMINEM (cont.): Ex:http://www.youtube.com/watch?v=xZwrteFNic4

How is Michael Moore guilty of the Ad Hominem logical fallacy in this video?Rather than attack George W. Bush for his politics or his ideas, he attacks his

character. Moore refuses to make a distinction here between George W. Bush’s statements and his personal habits.

Logical Fallacies (cont.)

#6.) FALSE DILEMMA:Poses an “either/or” situation by suggesting that only two options are

possible.*Sometimes called the “black/white” fallacy*Ex:“If you don’t watch football, you’re not a real man.”

How is this an example of the False Dilemma logical fallacy?This statement poses an “either/or” scenario in which a person either

watches football (therefore making them a “real man”) or that person does not watch football (in which case they are not a “real man”).

Logical Fallacies (cont.)

#6.) FALSE DILEMMA (Cont.):Ex:“Trust fund babies and corporate weasels are not allowed to read this book…

if you are in one of these categories, here’s my first piece of advice: you must learn to be a problem solver not a problem creator.”

-Bill O’Reilly, Who’s Looking Out For You?How is this an example of the False Dilemma logical fallacy? Bill O’Reilly poses a situation in which one is either a “problem solver” or a

“problem creator” without evaluating any middle ground in between the two.

Logical Fallacies (cont.)

#7.) SLIPPERY SLOPE:Claiming that one event will trigger a series of similar, undesirable events.*If an arguer fails to provide evidence to support his or her claim that one

event will lead to a similar, undesirable event, then they are guilty of the “slippery slope” fallacy.

Ex:“Cloning animals should be illegal because that would lead to cloning

humans, and then we would have a race of clones.”How is this an example of the slippery slope logical fallacy? The arguer assumes that if cloning of animals is allowed, then cloning of

humans will be too. Then, the arguer assumes that this hypothetical cloning of humans will grow out of control.

Logical Fallacies (cont.)

#7.) SLIPPERY SLOPE (Cont):Ex:“If they legalize gay marriage, then they will legalize bestiality and

pedophilia.” How is this an example of the Slippery Slope logical fallacy? The arguer jumps to the conclusion that if gay marriage is legalized, then

other undesirable things will also be legalized.

Logical Fallacies (cont.)

#8.) BEGGING THE QUESTION:A circular argument. When an arguer makes a statement that assumes that

the very question being argued is already answered.Ex:“Women should not be permitted into the men’s club because the club is

only for men.”How is this an example of the Begging the Question logical fallacy? The arguer does not adequately answer the original question (“why

shouldn’t women be permitted into men’s clubs?”). Instead, the arguer treats the question as if it has already been answered.

Logical Fallacies (cont.)

#9.) STRAW MAN:Setting up an extreme example of an opposing view to argue against.Ex:“Listen, you trust-fund babies and children of privilege, if you’re going to

drink a quart of bourbon every day and smoke crack, this book is not for you.”

-Bill O’Reilly, Who’s Looking Out For You?How is this an example of the Straw Man logical fallacy? Bill O’Reilly sets up an extreme example of “trust-fund babies” and

“corporate weasels.” His example is so extreme that it becomes very easy to argue against.

Logical Fallacies (cont.)

#10.) TWO WRONGS MAKE A RIGHT:A rebuttal to an argument which does not refute the allegations, but simply

counterattacks.Ex:“My step dad says I’m irresponsible, but I’m not. Besides, he’s a jerk.”How is this an example of the Two Wrongs Make a Right logical fallacy? The arguer does not refute the allegations that they are irresponsible;

instead, they simply counterattack.

Logical Fallacies (cont.)

# 11.) NON-SEQUITOR:A totally illogical connection between cause and effect.Ex:“Once rejected as ‘preposterous!’ Critics called it an outrage! It aroused

incredible antagonism in scientific and literary circles. Yet half a million copies were sold, and for twenty-seven years it remained an outstanding bestseller.”

-an advertisement for Immanuel Velikovsky’s book Worlds in Collision, a notorious flop.

How is this an example of the Non-Sequitor logical fallacy?The arguer assumes that simply because this book received a lot of publicity

that the book is a success. The arguer falsely connects cause and effect.

Logical Fallacies (cont.)

Logical Fallacies (cont.)

#12.) AD POPULUM:When an arguer assumes that he or she can neglect properly supporting his

or her argument by appealing to a thread of commonly held beliefsEx: