Learning to Think 101


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Some common logical fallacies.

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Learning to Think 101

  2. 2. Begging the Question A logic lapse committed when, instead of offering proof for its conclusion, an argument simply reasserts the conclusion in another form.  "Death for traitors is justified; because it is right to put to death those who betray our country."  "Why did he lose the election? He didn’t get enough votes.“  "When many people are out of work, unemployment results." (Calvin Coolidge.)
  3. 3. Complex Questions Some questions contain implicit assumptions, which may not be true. It is important to question the question.  "Have you stopped beating your wife?"  "Why is a ton of lead heavier than a ton of feathers?"  "Will you be paying by a check or a credit card?"  "Would you rather watch your baby sister or mow the lawn?"
  4. 4. Irrelevant thesis The attempt to prove a conclusion that is not the one at issue.  "The United States had justice on its side in waging this war. To question this would give comfort to our enemies and would therefore be unpatriotic."  "Vegetarianism is an injurious and unhealthy practice. For if all people were vegetarians, the economy would be seriously affected and many people would be thrown out of work."
  5. 5. Fallacy of Absent Control (False Cause) People commonly declare their washing their car enhances the chances of there coming up a rainstorm. "Every time I wash my car, it rains", they say. Well, maybe so, but the question is, how likely is it to rain if they don't wash their car?  "Twenty-five years after graduation, alumni of Harvard College have an average income five times that of men of the same age who have no college education. If a person wants to be wealthy, he or she should enrol at Harvard."
  6. 6. Ad Hominem a.k.a.: Attacking the Person A persuasion strategy in which a person attempts to defend her own position by pointing out the undesirable associations, personal characteristics, or motives of those who do not accept it.  The impact of the suggestion that "only bad people disagree with me" is often supplemented with an "all good people agree with me", introducing an appeal to diffuse authority. The big (and overlooked) question is: what has their badness or your goodness got to do with the truth of your position? The big (and overlooked) answer typically is "Nothing."  "Smoking is unhealthy. You should quit." "Hey! Look who’s talking! You smoke!"
  7. 7. Appeal to (Diffuse) Authority Definition: Defending a claim by citing, as a premise, the fact someone says or thinks as they do, where this person’s expertise (if any) is not relevant to the issue at hand, even though he may be someone who is famous or admired.  Comment: It's not necessarily fallacious, or irrational, to appeal to the judgment of authorities in support of a given statement. It is seriously irrational, however, to base your acceptance of a statement on the word of someone who doesn't know what they're talking about.  "No federal aid should be provided for public schools. My banker, my dentist, my doctor, my minister, and all my business associates are opposed to it."  "I join two presidents, twenty-seven senators, and eighty-three Congressmen in describing Drew Pearson as an unmitigated liar."
  8. 8. Appeal to Force Definition: A strategy to reduce the critical impulses of the listener by demonstrating or implying that it could dangerous to disagree with these statements.  "You must believe with me that this woman is guilty of the crime of which she is accused, for if you do not find her guilty of it, she will be released and you may end up being her next victim."  "Don’t argue with me, young man. Remember who pays your salary."
  9. 9. Appeal to Ignorance Definition: Uses an opponent’s inability to disprove a conclusion as proof of the conclusion’s correctness.  "No responsible scientist has proved that the strontium 90 in nuclear fallout causes leukaemia. Therefore we can disregard the alarmists and continue testing nuclear weapons with a clear conscience."  "If there were any real evidence for these so-called flying saucers, it would be reported in our reputable scientific journals. No such report has been made; therefore there is no real evidence for them
  10. 10. Appeal to Pity Definition: Seeking to support a statement by stating or suggesting that some person or creature the consumer cares about would be hurt or harmed by not accepting the truth of the proposition.  "Streaks of pain etching his youthful face, the boy drags his withered legs along the sidewalk, two crutches biting into the pavement one short step ahead. The minutes seem like hours, but the thinly built boy finally makes it to his destination, hangs up his coat and prepares for his day’s activities. When a handicapped boy pains himself by walking gruelling distances on hard wooden crutches, it proves that the handicapped will go out of their way to improve their lives. Now we ask you to do a little out of your way to help the handicapped."  "My client is the sole support of his aged parents. If he is sent to prison, it will break their hearts, and they will be left homeless and penniless. You surely cannot find it in your hearts to reach any other verdict than "not guilty."
  11. 11. Fallacy of Composition - NB Definition: An argument which requires, but does not defend, the premise that if all the parts of a whole (or members of a set) have some quality Q, then the whole (or set) will also have quality Q.  "They've got Amos McFnerk, the world's greatest centre.Two fantastic (great) forwards, and two awesome (great) guards. (Therefore) it's got to be a helluva (great) team!"  "I know one union representative and he is a terrible person. I wouldn’t trust any of them."  "Under the capitalist system, there are many poor people. Therefore, capitalism should be abandoned."
  12. 12. Confidence Strategy Definition: The practice of presenting a statement with style, volume, exclamation points, or other indicators of its truth, importance, or certainty, by way of concealing its lack of substantiation. Comment: Yelling is the most common confidence device. In more cultured circles, one simply attaches confidence phrases to one's statements– for example, "Obviously," "As anyone can see,", "Of course," etc., etc.
  13. 13. Domino Argument Definition: An argument characterized by a long chain of cause-to-effect inferences, leading from an apparently innocuous first step to a glaringly undesirable last one-- the upshot being that one should avoid the first step if at all possible.  You heard this sort of thing from your third grade teacher, who said she couldn't let you bring your pet turtle to school because if she did, then to be consistent she'd have to let every other kid bring his pet to school, and who knows, somebody might have an elephant!
  14. 14. False Dichotomy / ‘Black-White Fallacy’ Definition: An argument which requires such a statement as a premise, but does not defend it. "This isn't art-- it's vandalism!" Given the context of spray-painted graffiti on subway cars, we may assume that the presenter intended the judgment about art (an obscure subject) to be strengthened by the judgment about vandalism (plain to almost anyone). If so, there's a missing premise, namely "Either it's art or it's vandalism, but not both." This disjunctive statement may be true, but it isn't automatically true like "Either it's art, or it's not art" would be.
  15. 15.  "We can become independent of Arab oil only by ruining our environment."  "Volvo: the car for people who think."  "Either you drive a Jaguar, or you don’t drive at all."  "Life is like that, take it or leave it."  "Give me liberty or give me death."
  16. 16. Terminological Obfuscation Definition: The practice of disguising simple notions in complicated terminology, in order to conceal the true significance (or lack thereof) from the ordinary propositional consumer.  Comment: A chemist might refer to what's in the shaker on your table as "sodium chloride", or "NaCl". You may be baffled by these terms, but in fact they function to increase clarity and precision. On the other hand, when the CIA takes somebody out and shoots him, they may speak of it as "termination with extreme prejudice", but here the phrase hides the reality rather than revealing it details.
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