Unit 5: Syllogistic Reasoning

1. Unit 5: Syllogistic Reasoning Learning objectives: 1. Recognize and identify many common mistakes in reasoning that should not be, but often are, persuasive. 2. Avoid making these mistakes in your own thinking and writing. 3. Summarize and evaluate short passages that may contain more than one mistake in reasoning.

2. Meaning of Fallacy • Simply a mistaken belief • but we use it to refer to a deceptive argument • “Fallacies . . . are arguments that tend to persuade but should not persuade”

3. Fallacy • Fallacies are usually divided into two broad categories, “formal” and “informal.” • Formal fallacies are arguments involving invalid argument forms • Two of most common are • “affirming the consequent” • and “denying the antecedent,”

4. Fallacy • We will concentrate on informal fallacies • Not the form of arguments but their content.

5. Common Fallacies of Reasoning • Need not worry about classification methods (formal/informal or distraction/resemblance/appeal to emotion) • Important you can recognize fallacies • and able to state, clearly and concisely, what is wrong with them

6. Chapter 6: Bad Arguments • Fallacy - a bad argument that tends to persuade us even though it is faulty • Not all unsound or invalid arguments are fallacies • Arguments that tend to persuade but shouldn’t • 12 common fallacies

7. Chapter 6: Bad Arguments • Legitimate persuasive argument • premises audience believes and understands • structure that shows the conclusion follows • Illegitimate persuasive argument • inclines audience to accept • draws attention away from weak premise towards one more likely to accept • make you want to believe conclusion

8. Distraction Fallacies • Distract your attention away from the weak point of the argument • False dilemma • Slippery slope • Straw man

9. False Dilemma • Presents an either-or choice when there are really more alternatives

10. False Dilemma Example: Either we legalize drugs or we keep building new prisons and filling them with drug offenders. Implicit premise - we should not keep building prisons and filling them with drug offenders

11. False Dilemma • Arguer claims there are two alternatives and that one is unacceptable so we should choose the other • In fact there are more alternatives • Distracted about how undesirable one of the alternatives is • Forget to ask whether they are the only choices

12. False Dilemma Example: Either we legalize drugs or we keep building new prisons and filling them with drug offenders. (1) Either B or A Build prisons or legalize (2) Not A Not build prisons Therefore, B Legalize drugs

13. False Dilemma • False dilemma because the premise either A or B is not true • One premise and conclusion often left implicit • Often in the form “if you don’t choose A then left with undesirable alternative B”

14. Slippery Slope • Often object on the grounds that if this is done then something else will happen as a result... • then something else...then something else • ...to a situation that is clearly undesirable • May be good argument or a fallacy • Depends on having an acceptable premise • Fallacy when one if-then premise doubtful

15. Slippery Slope Example: Now they make us register handguns, the pretty soon it will be all guns. If that happens, then they’ll be in a position to take our guns away. We’ll be set up for a police state.

16. Slippery Slope Example: Now they make us register handguns, the pretty soon it will be all guns. If that happens, then they’ll be in a position to take our guns away. We’ll be set up for a police state. • Distracted by the outcome • Don’t question whether all the steps are connected - which is doubtful

17. Slippery Slope • If conclusion implicit it is usually the first step on the slippery slope should not be taken

18. Slippery Slope Example: We must keep the classics of European thought at the core of our college curriculum. If we continue to move our curriculum in a multicultural direction, quality will be sacrificed in the name of diversity. Pretty soon we’ll be treating pop music and pulp fiction as serious art. • Conclusion - The college should not continue to move curriculum in a multicultural direction

19. Straw Man • Make your own position appear stronger by making the opposing position appear weaker than it actually is. • Two premises in the argument are false • premise that inaccurately describes opponents position • (implicit) premise that you must either support this position or the position of the speaker (typically there are other alternatives)

20. Straw Man Example: Now is no time to reduce defense spending. Senator Toski claims we should spend less, but the senator apparently thinks the instability in Eastern Europe and in the Middle East pose no threat to our interests. • Attention drawn to weakness of argument to spend less on defense • Drawn to the conclusion that it should not be reduced • What do you really know of the Senators argument?

21. Straw Man Example: We desperately need a nationalized health care program. Those who oppose it think that the private sector will take care of the needs of the poor. But this has not been the case in the past and will not be in the future. • This argument can be refuted and is anyway irrelevant as to whether there should in fact be such a program.

22. Straw Man • Person committing the straw man fallacy cites someone else’s argument • Misrepresents the opposing view • Present a false either-or premise

23. Straw Man and False Dilemma • Straw Man We should ban all guns. Those who oppose a ban on guns don’t think very many crimes involve guns, but statistics prove otherwise. • Cites an opposing argument that is obviously weak • False Dilemma Either we ban all guns or we let crime run amok. • Claims only two alternative, of which one is unacceptable

24. Straw Man • Can come about in two ways • Refute an opponents position by listing only easily refuted premises in support of it • Misrepresentation of the premises, conclusion or both of the opponents argument

25. Straw Man Example: Now is no time to reduce defense spending. Senator Toski claims we should spend less, but the senator apparently thinks the instability in Eastern Europe and in the Middle East pose no threat to our interests. • Senator may have better reasons for his position, how much is enough for protection? • “apparently thinks” not quoted, an inference is being drawn

26. Straw Man • Destructive type of fallacy • Results in polarization and hardening of positions • Difficult to resolve disputes

27. Straw Man • Not claiming the conclusion is true or false • Just saying the argument given is inadequate • Not enough to just refute the opposition - have to provide arguments in support of your own position as well • Just because your opponents position is weak does not mean yours is any stronger

28. Exercise 6.1 b. I’m in favor of legalized gambling.There are those who oppose it, but they apparently think that anything that’s fun is sinful. Which fallacy and why?

29. Exercise 6.1 b. I’m in favor of legalized gambling. There are those who oppose it, but they apparently think that anything that’s fun is sinful. Straw man. This could be persuasive because your attention is caught by the weakness of the argument attributed to the opposition—anything that’s fun is sinful. But there are much stronger arguments against legalized gambling.

30. Exercise 6.1 g. see pictures on page 161 Which fallacy and why?

31. Exercise 6.1 • False dilemma - there are more “paths” than pure virtue or complete corruption. • Slippery slope - reading bad literature at age 13 isn’t all that likely to lead to the subsequent steps in the picture. • The argument might have been persuasive in its time because the disturbing thought of ending up an outcast could distract the reader from considering whether these are the only two paths and whether the steps down each path are really connected.

32. Resemblance Fallacies • Seem like good arguments because they resemble good arguments • affirming the consequent • denying the antecedent • equivocation • begging the question

33. Patterns • Affirming the consequent and denying the antecedent sometimes called formal fallacies because they have an incorrect form/pattern • This type of argument is bad because it is invalid • They resemble the two most common valid patterns modus ponens and modus tollens

34. Patterns • Affirming the consequent If A, then B B Therefore, not A If my car is out of fuel, then it won’t start My car won’t start Therefore, it is out of fuel

35. Patterns • Denying the antecedent If A, then B Not A Therefore, not B If you respected her opinion, then you would seek her advice. You don’t respect her opinion. Therefore, you won’t seek her advice.

36. Equivocation • When a word or expression shifts meaning from one premise to another.

37. Equivocation Example: You are perfectly willing to believe in miracles such as a person landing on the moon. If this is so, you shouldn’t be so skeptical of the miracles described in the Bible.

38. Equivocation Example: You are perfectly willing to believe in miracles such as a person landing on the moon. If this is so, you shouldn’t be so skeptical of the miracles described in the Bible. • Miracle in first sentence - something amazing, wouldn’t have thought it could be done. • Miracle in second sentence - something that defies the laws of nature.

39. Equivocation Equivocation is a bad argument because: • If the meaning of the terms are kept the same, one premise is false • If the meaning is allowed to shift, the argument is invalid

40. Valid pattern but one of the premises is false. Equivocation • Meaning kept the same (1) All murderers are (legally) insane people. (2) All (legally) insane people shouldn’t be punished. Therefore, all murderers shouldn’t be punished. All P1’s are P2’s All P2’s are P3’s Therefore, All P1’s are P3’s

41. Invalid pattern Equivocation • Meaning shifts (1) All murderers are (abnormally cruel) people. (2) All (legally insane) people shouldn’t be punished. Therefore, all murderers shouldn’t be punished. All P1’s are P2’s All P3’s are P4’s Therefore, All P1’s are P4’s

42. Begging the Question • Could be valid and have true premises • So why is it a fallacy?

43. Begging the Question • When the premise does not give a reason for believing the conclusion

44. Begging the Question Example: Whatever is less dense than water will float, because such objects won’t sink in water. • Premise is true • Conclusion follows - but simply restates the premise in different words • Technically valid but does not give a reason for believing the conclusion (1) A Therefore, A

45. Begging the Question • Obvious in a short argument • Not so obvious in a long argument to spot conclusion is just a restatement of one of the premises • One form is assuming in the premises the very thing to be proved • Arguing in a circle • Restate conclusion in same or different words as one of the premises

46. 1 1 p,c 2 2 p,c Begging the Question • Or one of premises is only accepted if you accept the conclusion Example: Abortion is murder. Therefore, abortion is wrong. • You would not say abortion is murder unless you believe abortion is wrong!

47. Emotion Fallacies • Confusing emotion with reason • Emotion can be a legitimate kind of appeal • But an appeal to emotion risks leaving a one-sided impression because of the way it can command your attention • Can provide a motive for belief rather than supporting reasons

48. Emotion Fallacies • To persuade you must engage peoples emotions - Aristotle • Emotions and reason should work together to produce conviction and action • Emotional fallacies • Appeal to force • Appeal to pity • Prejudicial language

49. Appeal to Force and Appeal to Pity • Appeal to pity - get you to agree because they will be hurt if you don’t • Appeal to force - get you to agree because they will hurt you if you don’t • Give you motive to believe the conclusion but not reasons in terms of evidence

50. Appeal to Force and Appeal to Pity • Appeal to pity • I am qualified for the job. I have a little experience in the area, and I’ve been out of work for two months so I really need the money