Avoiding Logical Fallacies

Transcription

1 Avoiding Logical Fallacies

2 Fallacy of Thought/Argument Fallacy comes from 2 Latin words: fallax or deceptive fallere: to deceive Oxford English Dictionary defines it as: Deception, guile, trickery Unreliability A sophism, that is, a misleading argument An error founded on false reasoning

3 Be Aware of Logical Fallacies Humans are instinctively self-deceptive and socio-centric We see what we want to see and hear what we want to hear We often go along with the beliefs of our parents, culture, religion without questioning

4 Unconscious Beliefs It is true if I believe it It is true if we believe it It is true if I want to believe it. It is true if it serves my purpose to believe it This is ego-centric, self-deceptive thinking

5 Role of Mass Media Designed to support uncritical thinking Reinforces stereotypes Discourages questioning Spin is all important Authority, power, and celebrity are praised It s all about social conditioning

6 Outsmart the Trick Since we know that humans tend to unconsciously think in a self-serving, egocentric manner, it is important to learn to recognize the most common tricks of persuasion/argumentative fallacies, that can trick and manipulate us.

7 DEFINING FALLACIES Critical Terms Needed to Understand Fallacies

8 Arguments Consist of: Premises Inferences Conclusions Arguments containing bad inferences, can certainly be called fallacious What is less clear is whether arguments containing false premises but which are otherwise fine should be called fallacious

9 Formal/Deductive Fallacies Deductive arguments are supposed to be water-tight For a deductive argument to be good (valid) it must: Be absolutely impossible for both its premises (both sides) to be true and its conclusion to be false the truth of the premises entails the truth of the conclusion.

10 Classic Example of Deductive Argument Premise: (1) All men are mortal. (2) Socrates is a man. Therefore (Conclusion): (3) Socrates is mortal. It is simply not possible that both (1) and (2) are true and (3) is false This argument is deductively valid Premise: (1) All men are mortal. (2) Socrates is a man. Therefore (Conclusion): (3) Socrates is immortal. Both (1) and (2) are true but (3) is false This argument is not deductively valid

11 Informal/Inductive Fallacies Good inductive arguments lend support to their conclusions Even if their premises are true, it doesn t establish with 100% certainty that their conclusions are true A good inductive argument with true premises might have a false conclusion

12 Inductive = Fallacious Premise 1: Most American cats are domestic house cats. Premise 2: Bill is an American cat. All inductive arguments (even good ones) are therefore deductively invalid and can be said to be fallacious. Conclusion: Bill is domestic house cat.

13 Terminology for Inductive Fallacies Because ALL inductive arguments are considered false, different terminology is needed to distinguish good and bad inductive arguments. Most often used terms: Strong Weak

14 Example of Strong Inductive Argument Premise: (1) Every day to date the law of gravity has held. Therefore (Conclusion): (2) The law of gravity will hold tomorrow.

15 Example of Weak Inductive Argument: (1)The last ten times I played poker, I won money. (2) I m playing poker tonight. (3)I ll win money tonight.

16 Informal Arguments Arguments that fail to meet the standards required of inductive arguments Known as informal fallacies Most often described by guides to good thinking Primary concern of most critical thinking courses

17 Informal Arguments (cont d) If a fallacy is an error of reasoning, then such arguments are not fallacious Their reasoning/logic, is sound However, many traditional fallacies are like this, so we Define fallacy in a way that includes them Include both formal and informal

18 THE 10 DEADLY FALLACIES How to Recognize Them and Avoid Them

19 # 1: Faulty or Hasty Generalizations Generalization is essential to communication Not all generalizations are faulty Cow 1 is not cow 2 is not cow 3 Examples: Everybody knows ; All people ; It is obvious that ; No one understands We also generalize when we make assessments about a person s character after 1 encounter

20 Being Accurate, Precise, and Less Biased Don t say all when you mean most Don t say most when you mean some Don t say some when you mean a few Don t say a few when you mean one

21 #2: Ad Hominem Latin for to the man Attack the person and not the argument Politicians like to use this one Bill Clinton was a bad president because he had sex with an intern makes an argument that is not based on his record but on his character Uses name calling and mud-slinging.

22 #3: Post Hoc Ergo Propter Hoc /Faulty Causality After that, therefore caused by that Presumes that if one thing happens after another one, the first causes the second Examples: I got a stomach ache after algebra class. Therefore, I d better avoid algebra. The president raised taxes last year, and the crime rate went up this year. Therefore, the crime rate went up because of the tax increase.

23 #4: The slippery slope * Implies that if someone does one thing, it will inevitably lead to a domino effect that will result in something terrible Remember, kissing leads to sex, which leads to an unwanted baby, and your life will be ruined! *that leads to disaster

24 #5. Straw man A false or misleading representation of someone s position in an argument Example: Person A wants to reform the prison system. Person B argues: Well, I guess you want to free all the criminals and leave us unprotected. The argument is not against what A said, so it is not real.

25 #6: The Bandwagon Everybody s doing it, so it must be a good idea In truth, just because something is popular, it is not necessarily a good thing Example: But mom, everybody is bungee jumping. Now I ll be left out, and my friends will make fun of me if you don t let me.

26 #7: Gambler s Fallacy Assuming that shortterm deviations from probability will be corrected in the short-term when faced with a series of events that are statistically unlikely Example: A series of 9 coin tosses have landed heads-up it is very tempting to expect the next coin toss to land tails-up The past series of results, though, has no effect on the probability of the various possible outcomes of the next coin toss

27 #8: Tu Quoque Asking a question that has a built in presumption, so that you can t answer without seeming guilty Example: How long have you been beating your wife?

28 #9: Begging the Question Presenting a circular argument in which the conclusion is included in the premise Example: The word of Goku is flawless. We know because it says so in the Book of Goku, which we should not question.

29 #10: Appeal to Authority Similar to #9 Belief that because an authority says something it must be true Examples: But my professor says there s no such thing as gravity, and he has a Ph.D., so he must be right. Global warming isn t real because this scientist says so.

30 So To avoid logical fallacies always make sure you are getting your information from reliable sources and always ask questions!

31 Be A Critical Thinker! A critical thinker: Encourages self-insight Lacks the desire to manipulate or control others Envisions a more ethical world Is acutely aware of the phenomenon of mass persuasion through media Questions the means and ends of any given situation Sees through dirty tricks of manipulative persuasion

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