What is a logical fallacy?

Transcription

1 Logical Fallacies

2 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: All birds have beaks. A squid has a beak. Therefore, a squid is a bird. *With deductive fallacies, an arguer makes an incorrect or unsupported link between cause and effect*

3 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.

4 #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.

5 #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.

6 #2.) FAULTY USE OF AUTHORITY: Falsely recognizing someone as an authority on something. Accepting someone s credentials without careful evaluation. EX: 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.

7 #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.

8 #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.

9 #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.

10 #4.) FALSE ANALOGY (cont.): Drawing an analogy or comparison between two situations that are totally dissimilar. Ex: Employees are like nails. Just as nails must be hit in the head in order to make them work, so must employees. How is this an example of the False Analogy logical fallacy? The arguer assumes that nails and employees are analogous. She assumes that a method that works for a tool will work for a person.

11 #5.) AD HOMINEM: Attacking a person s character rather than their statements. Latin for to 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.

12 #5.) AD HOMINEM (cont.): Ex: 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.

13 #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 ).

14 #6.) FALSE DILEMMA (Cont.): Ex: 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.

15 #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.

16 #7.) SLIPPERY SLOPE (Cont): Ex: If they legalize marijuana, then they will legalize heroin, then they will legalize suicide, then they will legalize murder. How is this an example of the Slippery Slope logical fallacy? The arguer jumps to the conclusion that if marijuana is legalized, then other undesirable things will also be legalized.

17 #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.

18 #8.) BEGGING THE QUESTION(cont.): Ex: The reason everyone wants the new "Slap Me Silly Elmo" doll is because this is the hottest toy of the season! How is this an example of the Begging the Question logical fallacy? The arguer does not adequately explain the original issue( the reason everyone wants an Elmo ). Instead, the arguer treats the question as if it has already been answered.

19 #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.

20 #10.) TWO WRONGS MAKE A RIGHT: A rebuttal to an argument which does not refute the allegations, but simply counterattacks. Ex: My stepdad 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. The arguer assumes that if the stepdad is wrong, it justifies his actions.

21 # 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.

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23 # 11.) NON-SEQUITOR: A totally illogical connection between cause and effect. Ex: David eats broccoli. David should love to eat meat. How is this an example of the Non-Sequitor logical fallacy? The arguer assumes that liking one food is related to another. The arguer falsely connects cause and effect.

24 #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 beliefs Ex: