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Informal Fallacies:
Test Answers

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Directions: Please indicate two best answers to the fallacies in each of the following passages:

1. Old man Brown claims that he saw a flying saucer in his farm, but he never got beyond the fourth grade in school and can hardly read or write. He is completely ignorant of what scientists have written on the subject, so his report cannot possibly be true.
Ad hominem: Brown's education is irrelevant to his what he reports that he observed.
2. My client is an integral part of this community. If he is sent to prison not only will this city suffer but also he will be most missed by his family. You surely cannot find it in your hearts to reach any other verdict than “not guilty.”
Ad misericordiam: The pity being invoked for the client is not relevant to the determination of his guilt or innocence.
3. You ought to try to study harder in school this year, Samuel, because it will spare your parents the embarrassment of a letter from the instructor telling them you're slipping.
Ad baculum: The reasons for Samuel to study should be independent of the threat to inform his parents.
4. You will back up my story and tell the committee I am reasoning logically; because if you don't I will do everything in my power to see that you are fired.
Ad baculum: The threat of being fired, presumably, is not logically relevant to the purported story.
5. I believe in the Bible because it is the written word of God through his prophets. Obviously, God would not lie to his prophets. After all, the Bible says so.
Petitio principii: A premise and final conclusion are paraphrases of each other; hence the argument is the fallacy of the structure of circulus in probando.
6. Congress shouldn't bother to consult major universities about educational appropriations. As members of educational establishment, they will naturally want as much money for education as they think they can get.
Ad hominem: Reasons should be evaluated on their own merits not necessarily on the character of the persons issuing them. Although the premise is probably true, the educational establishment is probably worth consulting about relevant educational factors of which the government might be unaware.
7. In recent studies researchers have show that women have more accurate intuition than men do. The reason cited is that men's intuition is more often mistaken.
Petitio principii: The premise and conclusion are both probably true, but since premise and conclusion are equivalent propositions, what is to be proved is already assumed in the premise. The structure of the argument is hysteron proteron.
8. I can see that you are in the market for a new car. We're having a sale on the Pinto sedans this month you cannot not miss. So do you want to pay cash or do you want the installment plan?
Complex question: The phrasing of the question presupposes the conclusion that you want to purchase a Pinto sedan.
9. John has really worked hard on his term project, and he will really be depressed if he does not make an A. For these reasons, you just have to grant him an A on his project.
Ad misericordiam: Presumably the grade on the project is determined by the quality of the work accomplished — not on John's feelings. Nevertheless, John should be provided with the reasons for the evaluation of his project.
10. What is right is what is morally obligatory. What is morally obligatory is what you should do. Of course, you should do something because it is the right thing to do.
Petitio principii: A premise and conclusion in this argument chain are logically the same. The version is circulus in probando.
11. I can see that you like the efficiency with which the Tornado Home Vacuum System works and that you are impressed with the marvelous way in which it saves on toil and drudgery in the home. Therefore, shall I charge it to your account or would you prefer to pay cash?
Complex question: The conclusion that you are buying the vacuum system is being presupposed in the question posed.
12. If we wish to determine which of a person's motives determine his actions, we need only examine which of the alternative courses of action he chooses to perform. Therefore, a person's motives are determined by the actions he chooses to perform.
Petitio principii: The conclusion is being presupposed in the premise.
13. A prosecutor states to the jury: “You cannot let this man go free because our society is not safe with him at large. Who knows who his next victim might be?”
Complex question: The prosecutor is not warranted in presupposing without proof that the defendant is guilty of the crime charged — he is assuming a verdict which is precisely the finding to be proved.
14. It should be no surprise to you that if a Democrat is elected in the next presidential election, we will have one of the worst recessions in years. Recessions always seem to be created by Democratic administrations.
False cause (non causa pro causa): No causal mechanism is shown for the relation between events stated even though there might be some evidential past correlation. The version of the fallacy here is post hoc ergo propter hoc.
15. As I walked to the library from the Learning Center not one person spoke to me. This university is not as friendly as I was led to believe.
Converse accident: The generalization that many or most people at the university are unfriendly is reached from one circumstance; one experience is not enough evidence to form a reliable conclusion.
16. How can we save our country from the bureaucratic dictatorship, the corruption, and the creeping socialism of the present administration? There's only one way: vote Independent.
Complex question: The presupposition of this question might not be generally granted. Before opposing the present administration, the presupposed circumstances alluded to need to be shown to be the case.
17. I don't care what your arguments are; you are using Mickey Mouse tactics. The arguments you give are simply cheap and tacky.
Ad hominem: Character attacks and name calling are irrelevant to the cogency of the arguments proposed. The descriptions characterizing the arguments do not explain their logical inadequacy.
18. Officer, please excuse my going over the speed limit, but my mother is ill, I'm being audited by the IRS, and I don't know how I can meet all my bills. You can't believe the pressure I'm under. I really need this break.
Ad misericordiam: The pity being attempted to be invoked is irrelevant to the question at issue, namely that of whether or not the person committed a traffic violation. The problems listed are irrelevant to whether or not a traffic violation occurred.
19. Why haven't you been studying, as you should? You would feel a lot better if you would take you school work more seriously.
Complex question: The complainant is assuming without proof that you have not been studying. The presupposition of the question requires evidence before posing.
20. Those who say that extra-sensory perception is not reliable are mistaken. The police, Hollywood stars, and politicians have all relied on psychic abilities.
Ad populum Simply because many persons believe something does not thereby make the belief true. One might argue here, as well, the fallacy of ad verecundiam occurs since the persons cited are not known to be authorities in the field of psychic phenomena.
21. But Doctor, surely your advice that I should not drink coffee is not sound advice since you yourself often drink coffee.
Ad hominem (tu quoque): Mention of the doctor's habits are irrelevant to the recommendation made. The reasons for medical advice usually differ according to the various distinct health conditions of the patient.
22. The late Ellie Culbertson, one of the world's outstanding bridge players, once declared that the United Nations as presently constituted has serious defects. She must be right because I don't think the opinion of woman of that caliber should be taken lightly.
Ad verecundiam: The bridge authority is being quoted outside of her field of expertise. If she were an authority on the UN, that expertise, rather than her bridge abilities, would ordinarily be acknowledged.
23. The General Assembly of the United Nations keeps voting for radical issues. We cannot allow this to continue. Therefore, the U.S. will soon be forced to reduce its financial contribution to the U.N. unless there is a demonstrated change in the coming days.
Ad baculum: The arguments themselves need to be evaluated rather than side-stepping the issues raised by irrelevantly threatening to withdraw previously committed or promised support for the international peace organization. (Presumably, the “radical” issues being discussed are not outside of the articles of U.N. Charter.)
24. During the Gulf wars many Americans made, and continue to make, immense profits. That is an indisputable fact. Therefore, there can be no doubt that American business interests played an active role instigating and continuing these wars.
False cause (post hoc ergo propter hoc and cum hoc ergo propter hoc): Simply because two events occur together, one cannot assume that one caused the other without further evidence being adduced.
25. No mathematician has ever been able to demonstrate the truth of the famous Goldberg conjecture for the four-dimensional total space of an almost Hermitian submersion, so it undoubtedly must be false.
Ad ignorantiam: From the fact that there is no proof of the conjecture, no conclusion as to its truth or falsity can be drawn.
26. Everyone says that a logic course is easier than a math course, so if you want to keep up your grade-point average, don't enroll in the math course.
Ad populum appeal: Common belief could be mistaken. Even so, it is arguable that previous student opinion provides evidence for the degree of difficulty of specific courses. So even though the advice is an ad populum appeal, it is not fallacious since it is a credible inductive argument providing some evidence for the truth of its conclusion.
27. Unless you back up my story and tell the committee I am reasoning logically, I'll do everything in my power to see that you are fired.
Ad baculum: The threat of force in this example is irrelevant to the question of the credibility of the story.
28. The best students make the best grades. Therefore, getting high grades will undoubtedly lead to your being a better student.
False cause (post hoc ergo propter hoc): Even assuming the truth of the premise the the best students make the best grades, it does not follow that receiving undeservedly high grades will cause someone to be a better student. The awarding of undeserved high grades could quite possibly encourage someone to study less. (Notice why this fallacy is not petitio principii: it is an invalid conversion of an A statement. “All S is P” is not in general equivalent to ”All P is S.”)
29. Everyone believes that men write the best novels; therefore, there is little doubt that they do so.
Ad populum appeal: Even if one were to assume the truth of the premise, popular opinion does not prove the quality of a novel. Writing quality is effected by such measures as striking imagery, variety of sentence types, specific and precise wording, and a convincing point of view. Admittedly indicators such as these have some effect on reader appeal. Since no evidence is provided for the questionable premise (that men write the best novels), some logicians in centuries past have described an initial unsupported questionable or false general premise as a hasty generalization. However, in our course a fallacy is defined as a logical mistake in argument — not a false or questionable assumption.
30. Since the Bible says, “Thou shall not kill,” it would be ethically mistaken to exterminate the rodents in City Hall.
Accident: The reasoning in this example proceeds from a general principle (or commandment) to an atypical specific application of the rule not meant to be subsumed under that rule.
31. But Mom I don't see why I have to wear socks; Einstein never did wear socks.
Ad verecundiam: Einstein's field of expertise does not extend to the wearing of socks. He's being quoted outside of his area of authority. (Note: This is not an example of false cause — there is no suggestion here that the non-wearing of socks will cause someone to be an “Einstein.”)
32. I once knew a philosophy student who went crazy and another one who did not seem that well-balanced. It's pretty obvious to me what the study of philosophy did to them.
False cause (post hoc ergo propter hoc): No causal mechanism is being proposed for the causal link between philosophical study and psychological health.
33. A great many charges of graft and corruption have been brought against Senator Anderson over the past several years, and he has had numerous opportunities to refute them, but he has never done so. Therefore, I conclude the evidence indicates he is not to be trusted.
Ad ignorantiam: From the fact that there is no proof or evidence provided, no conclusion can be drawn. This is not to say, however, that there is no reason for suspicion of the Senator's conduct.
34. The present U.S. administration has not yet developed a consistent energy policy. Nonetheless, almost every other developed nation in the world has an energy policy, except us. Therefore, the United States should seek to develop a consistent and unified future policy.
Ad populum: The popularity of a practice or a belief internationally is not, by itself, sufficient to establish its necessity for the U.S. An adequate energy policy rationale for the U.S. could presumably provide such a reason.
35. The welfare program is totally unnecessary. Why, I know a guy who runs a very lucrative illegal gambling operation and drives his new Cadillac down every week to collect his welfare check.
Converse accident: One instance is insufficient to establish the truth of a generalization. One person taking advantage of a welfare program is insufficient evidence to show that the welfare program is unnecessary.
36. The accident was his fault, Officer. You can tell by the kind of car I'm driving and by the kind of clothes I'm wearing that I'm a good citizen and would not lie. Look at the rattletrap he is driving, and look at how he is dressed. You can't believe anything that a dirty, long-haired hippie like that might tell you. Search his car; he probably has drugs in it.
Ad hominem: The attack on a person's character is not relevant to the question of which party might be the cause of the accident. The cause of the accident is determined by grounds other than a person's appearance.
37. General Jed M. Lamgetter believes that it is absolutely essential to our future security that we immediately upgrade our computing systems to the Red Hat Linux distribution from our current Microsoft boxes. But his arguments are hardly deserving of careful consideration, for in a couple of weeks General Lamgetter will retire from the Army, become CEO, and be given large stock options in the Red Hat Corporation, one of the main providers of business enterprise open-source products.
Ad hominem: General Lamgetter's circumstances in this instance not are not logically relevant to the truth or falsity of his assertions. His are suspicious circumstances, but the decision for upgrading the computing systems should be based on factors such as the quality, support, training, and reliability of a computing system.
38. The real reason you favor armed services conscription is that you're too old to be drafted.
Ad hominem: The personal attack, even if true, is not relevant to the rationale for selective service system conscription. The arguments for Congressional authorization of the draft should be based on other factors.
39. Why don't you answer me? I've already asked you twice. I know — you're either covering something up or you're afraid to reply.
Ad ignorantiam: No conclusion can be drawn from the lack of information. There are many possible reasons for not responding.
40. Stanford University produces the best graduates in the United States. Therefore, any Ph.D. from Stanford is better than any other Ph.D. in the country.
Fallacy of Division: The quality of the whole does not necessarily extend to the individual elements.
41. Water extinguishes fire. Oxygen is part of water. Therefore, oxygen will extinguish fire.
Fallacy of Division: The parts of a compound do not necessarily have the same qualities of the compound itself.
42. Priests take a vow of poverty. The Church is a corporate body composed of priests. Therefore, the Church should not own property.
Fallacy of Composition: The parts of something do not necessarily have the same characteristics as the whole of that something.
43. Since the average life-span of an individual in developing countries is thirty years, the leaders in those countries grow old before they have time to learn the rudiments of good government.
Fallacy of Division: The average life-span does not apply distributively to the individuals cited in a particular country. High infant mortality in many developing countries skews the normal distribution of life-span. Once an individual lives beyond the early years in developing countries, the average life-span is much longer than the overall average life-span for that country.
44. As the convener of the ninth annual Women's Freedom Movement, let me remind you once again that women have been discriminated against for centuries, and they have suffered as second-rate people for centuries. I, for one, have had enough, and I refuse to submit to this discrimination and second-rate treatment any longer.
Fallacy of Division: The speaker cannot have lived for centuries and cannot have suffered for centuries. The quality of “suffering for centuries” can apply to the group as a whole, but does not apply to any particular individual.
45. I ought always to do what is right. I have a right to say what I think. Therefore, I ought always to say what I think.
Fallacy of Equivocation: The word “right” is being used in two different senses. The first sentence uses the word “right” to mean “morally good” or “morally acceptable.” The second sentence uses the word to mean “legally entitled.”
46. As a result of a poll of 28 adults interviewed on Main Street on last Friday night, we can safely conclude that most people in this town prefer going downtown to watching Netflix on Friday nights.
Converse accident: The samples collected are atypical of the population as a whole since the data were collected exclusively at only one of the two situations mentioned in the poll.
47. According to the law, a man is innocent until proved guilty. So Mr. Ratskeller must be legally innocent of the charge of bribery, since he has not yet been proved guilty. Therefore, your Honor, since Mr. Ratskeller is innocent, I don't see what this trial is all about.
Fallacy of Equivocation: Two different senses of the word “innocent” are being used in the argument: legal and actual innocence.
48. Although you have said you will give me no more of your time, I'll not ask for any more of your time; I'm only asking for the same amount you've already given and no more.
Fallacy of Amphiboly: The loose combination of words leads to two different interpretations for the phrase “more of your time”: “no more time whatsoever” and “no more additional time than that given before.”
49. In response to your inquiry as to my opinion of the candidate, I can tell you as his two-year supervisor that most enthusiastically recommend this candidate with no qualifications whatsoever.”
Fallacy of Amphiboly: The loose and awkward construction of the sentence leaves open the question as to whether or not the candidate is qualified. Does the candidate have no qualifications whatsoever or does my recommendation have no qualifications whatsoever?
50. A poor grade on this test is better than nothing, and nothing is better that a high grade. So I logically conclude a poor grade on this test is better than a high grade.
Fallacy of Equivocation--Two different senses of “nothing” are being used in the argument. The first use is “no grade at all” and the second use is “no grade exists higher than a high grade.”



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