Table of Contents
Part I: You must answer #1 (3 points)
1.) We discussed the distinction between necessary and sufficient conditions. A.) Give an example of something that is a necessary but not a sufficient condition for something else. First, state this in the form “X is necessary but not sufficient for Y.” Second, state this in the form of a conditional. B.) Give an example of something that is a sufficient but not a necessary condition for something else. First, state this in the form “X is a sufficient but not necessary for Y.” Second, state this in the form of a conditional. C.) Give an example of something that is both a necessary and sufficient condition for something else. First, state this in the form “X is necessary and sufficient for Y.” Second, state this in the form of a bi-conditional.
*Note: you may not use any examples from the textbook or the handout. Also, your examples may specify necessary and/or sufficient causal conditions, but they need not do so (remember, not all conditions are causal).
A. Condensation nuclei are necessary but not sufficient for clouds to form.
If there are condensation nuclei, then clouds will form.
B. Spicy food is sufficient to cause heartburn, but not necessary for heartburn.
One will only get heartburn if they eat spicy food.
C. A virus is necessary and sufficient to transmit influenza.
A person can only be infected with influenza if they get the virus.
Part II: Conceptual Analysis. The following conceptual analyses are defective in certain ways. They may be too broad, they may be too narrow, they may be both too broad and too narrow, or they may fail to elucidate. State and explain why each analysis is defective (i.e., it is not sufficient simply to say “this analysis is too broad”; you must explain why it’s too broad. If an analysis is too broad or too narrow or both, you should show this by citing a counterexample).
*The following analyses may be defective in more than one way.
*Note: I wish to remind you of something I pointed out in class: “failing to elucidate” doesn’t simply mean that the analysis in question contains vague terms. It either means that the analysis is circular, or it means that it employs terms that are too close to or more obscure in meaning than the concept being analyzed; it either analyzes the concept in question in terms of either synonymous or other closely related concepts, or it analyzes the concept in question in terms of other concepts that are just as difficult (or more difficult) to understand. So, you cannot criticize any of the following analyses by simply saying that it employs vague terms. If think that an analysis fails to elucidate, you must either point out that the analysis contains terms that are too close to the one being analyzed, or that the terms employed in the analysis are just as difficult or more difficult to understand as the term being analyzed.
Answer TEN (2 points each)
3.) An animal is a dog if and only if it barks and has canine DNA.
This analysis is too narrow as criteria for an animal being classified as a dog. There are dogs that are not able to bark, which could be due to trauma, birth defect, or training. Therefore, using only these two classifications would exclude many dogs.
7.) A person is a good student if and only if he/she regularly attends all of his/her classes and regularly performs well in all of his/her classes.
This criteria is too narrow to determine a good student. A student may not be able to attend classes regularly, which could be due to illness, disability, other engagements, etc. Students also have their strengths and weaknesses and may not be strong in every subject they take. As well, there are students that attend classes regularly but do not pay attention. The criteria should be that they are engaged when present, eager to participate and perform well in most of their classes or make the effort to perform well.
9.) A person is generous if and only if he/she regularly donates money to charity.
This analysis is too narrow to show someone’s generosity. People may be generous in other ways than giving money to charity. There are those that are skeptical about charity foundations but still donate money in other ways. From this analysis it could also be assumed then that poor people are not generous as they have no money to give to charity, which is not a factual analysis. People can also give their time, skills, or other talents to others in generous ways. The analysis should be more general to include those that donate in other ways, and those who have no money to give.
10.) An argument is good if and only if it’s valid.
This assumption is both broad and narrow at the same time. It is quite broad in the sense that validity can be left up to personal judgment and ethics. Not everyone may possess the same level of education to have knowledge on a topic to deem it valid, and not everyone possesses good discernment. The assumption can be seen as narrow, as it does not take into account factors or subjects that cannot be proven outright, but is believed by the person arguing. This may include personal experiences or beliefs.
11.) An action is selfish if and only if the agent who performs it desired to perform it and derives pleasure from having performed it.
This analysis would assume that people deriving pleasure from an action is negative and selfish. This is a narrow analysis of selfishness and is also inaccurate. There are actions that can be performed by one that is beneficial to many other people and nature, and the person completing the action can still derive pleasure from it.
12.) X is a planet if and only if it is a celestial body that orbits a star.
This criterion for a planet is too broad. There are many celestial bodies such as asteroids or satellites that would then be considered to be planets under this analysis. It helps in one way to define what a planet is in that it must orbit a star, but must include more specific criteria such as its size or weight and stable shape.
17.) An action is morally right if and only if it is legal.
This analysis supposes that there is a correlation between legality and morality which makes the definition of a morally correct action too narrow. It also supposes that all things legal are moral, which may not be accurate. An action could be illegal but may be morally correct based on culture or beliefs of the person performing the act. While legal statutes or regulations may not be morally correct at times such as giving a person or corporation a permit to conduct activity that may pollute the environment or harm another person.
19.) An object is a work of art if and only if it is beautiful and resembles an object in nature.
The criteria stated here for labeling a piece a ‘work of art’ is too narrow. It art it is often stated that beauty s in the eye of the beholder, and therefore there is no one object that will be considered beautiful to all people. Therefore, there would be no works of art by this criterion. Artists often create from imagination and so there are many pieces of arts that would not be classified as such, since they do not resemble something in nature.
22.) A law is just if and only if it is passed by majority vote.
This definition of just law is too narrow to encompass the whole population or voting population. There may be those who were unable to vote, whose point of view would not be considered. There is also the assumption that justice is denoted by majority vote instead of by ethics or other means. Those in the minority for whatever reason could have just cause to vote otherwise as well, and their point of view would not be considered just by this standard.
24.) A group is a society if and only if it is composed of members who live close to each other.
The analysis for the definition of a society is too narrow and contains only the criteria that the live close to each other. There are people who share likeminded interests that live miles away from each other, but collaborate to form a society, and on the other hand there are those who live close to each other but share no camaraderie. The definition should be more inclusive and broader.
Part III: Deductive Arguments. The following arguments are Deductive A.) For each example, first identify the specific pattern of deductive reasoning (is it a categorical syllogism? Modus Ponens? Hypothetical Syllogism? Denying the Antecedent? Etc…) B.) Second, evaluate the validity of the argument. If the argument is valid, just say so. If the argument is invalid, say so, but state the formal fallacy that the argument commits (fallacy of the undistributed middle? Illicit major or minor? Affirming the consequent? Denying the antecedent? Etc…Note: since some formal fallacies – e.g., affirming the consequent – are identical to the pattern of reasoning you will have identified in part A, just state that this is an invalid form).
*Note: it is not necessary to standardize the following arguments, though in certain cases you may find it helpful to do so in order to determine the pattern of reasoning.
Answer TWENTY (1 point each)
31.) If you wait to write your paper until the night before it’s due, then the best grade you’ll receive on it is a C, and since you did wait to write your paper until the night before it’s due, the best grade you’ll receive on it is a C.
Hypothetical syllogism. The argument is invalid and uses fallacy of the undistributed middle
32.) No freshmen will graduate this year, and some students in this class are freshmen, so no student in this class will graduate this year.
Categorical syllogism. The argument is invalid and uses illicit major.
33.) Jack is bound to sharpen his reasoning skills, for Jack is enrolled in a critical thinking course, and anyone enrolled in a critical thinking course is bound to sharpen his reasoning skills.
Modus ponens. The argument is invalid as it is affirming the consequent.
34.) Some astronauts are engineers, and some astronauts are scientists, so some scientists are engineers.
Categorical syllogism. The argument is invalid and uses illicit minor.
35.) Either the North won the civil war, or Bigfoot exists; the North did not win the war; so, Bigfoot exists.
Categorical syllogism. The argument is invalid and it is affirming the consequent.
36.) All people with things to hide plead the fifth, and Chris pleaded the fifth, so Chris must have something to hide.
Hypothetical syllogism. The argument is invalid is affirming the consequent.
37.) Where is the stock market headed? Some think we are in the middle of a sustained bull market. My view is that stock market prices will go down this coming quarter because if interest rates go up, stock market prices will go down, and the Federal Reserve has indicated that interest rates will rise.
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Modus ponens. The argument is invalid as it is affirming the consequent.
38.) If you’re a socialist, then you supported Obama, and if you hate free-market capitalism, then you supported Obama; so, if you’re a socialist, then you hate free-market capitalism.
Hypothetical syllogism. The argument is invalid and uses illicit major.
39.) All of Dickens’ novels are social commentaries. Some social commentaries are not works of lasting interest. So, some of Dickens’ novels are not works of lasting interest.
Categorical syllogism. The argument is invalid and uses illicit minor.
40.) J.D. will either see Lincoln or Skyfall this weekend, but since he’s going to wait a couple of weeks to see Lincoln, he’s going to see Skyfall this weekend.
Modus ponens. The argument is invalid and it is affirming the consequent.
41.) It cannot be true that good living is just doing whatever I want to do. If it were, then it would in principle be impossible for me to want something that is bad for me. But it is evident that I do sometimes want to do things that are bad for me, like drinking with my friends the night before an important exam, eating all of the pecan pie, and spending money that I don’t really have.
Denying the antecedent. The argument is valid.
42.) Some females are not mothers, and some politicians are not females, so some politicians are not mothers.
Categorical syllogism. The argument is not valid, and uses illicit minor.
43.) If J.D.’s girlfriend broke up with him, he’d be really depressed. I just saw him, and he seemed really depressed, so his girlfriend must have broken up with him.
Modus ponens. The argument is invalid and is affirming the consequent.
44.) Some explosives are chemicals, from which it follows that some purchasable items are not chemicals because no explosives are purchasable items.
Denying the antecedent. The argument is invalid as the premise may be true but the conclusion is false.
45.) “The governments, not only the military ones, but governments in general, could be, I do not say useful, but harmless only in case they consisted of infallible, holy people. But the governments, by dint of their very activity, which consists in the practice of violence, are always composed of elements which are the very opposite of holy – the most impudent, coarse, and corrupted men. For this reason every government…is a most dangerous institution.” – Leo Tolstoy, “Patriotism and Government”
Modus ponens. The argument is invalid and uses fallacy of the undistributed middle.
46.) Some professors are not democrats and all professors are college graduates. Therefore, some democrats are not college graduates.
Categorical syllogism. The argument is invalid and uses illicit minor.
47.) Either my book is in my bag, or I left it in the library, and my book is not in my bag, so I must have left it in the library.
Hypothetical syllogism. The argument is invalid as it is affirming the consequent for reasoning.
48.) All conservatives believe in private property, and all people who defend capitalism believe in private property, so all people who defend capitalism believe are conservatives.
Hypothetical syllogism. The argument is invalid and uses fallacy of the undistributed middle.
49.) If you wish to understand Merleau-Ponty’s philosophy, then you have to understand Descartes’ philosophy, for if you wish to understand Merleau-Ponty’s philosophy, you have to understand Husserl’s philosophy, and if wish to understand Husserl’s philosophy, you have to understand Descartes’ philosophy;
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Hypothetical syllogism. This argument is invalid and uses illicit minor.
50.) All horses are quadrupeds, and no humans are horses. Thus, no humans are quadrupeds.
Denying the antecedent. The argument is invalid as the conclusion may be false even if the premise is true.
Part IV: Non-deductive Arguments. The following arguments are non-deductive. A.) For each example, identify the kind of non-deductive argument that it is (Conductive? Inductive generalization? Statistical syllogism? Argument from analogy? Casual?). B.) Second, evaluate the strength of the argument. If the argument is strong, explain why. If the argument weak, explain why (is it a hasty generalization? Is it based on a biased sample? Why? Does it commit a post hoc fallacy? Does it confuse cause and effect? Does it ignore a common cause? Slippery Slope? Weak analogy? Why?, etc…the following arguments may commit any of the fallacies of induction we covered, and some may not commit any fallacy at all).
*Note: Certain non-deductive arguments will require longer explanations than others. For example, if a non-deductive argument commits the fallacy of a biased sample, you must articulate why. If it’s a strong generalization, you must explain why, but that will probably only require a sentence or two. If an argument commits a slippery slope fallacy, all you need to do is to say so. However, if the argument is a strong or weak analogy, you must explain why, and that might require a paragraph. In any case, you can’t just state that the argument is strong or weak – you must give reasons for why it is so.
Answer TWENTY (2 points each)
76.) “I'd like to share a revelation that I’ve had during my time here. It came to me when I tried to classify your species, and I realized that humans are not actually mammals. Every mammal on this planet instinctively develops a natural equilibrium with the surrounding environment; but you humans do not. Instead you multiply, and multiply, until every resource is consumed. The only way for you to survive is to spread to another area. There is another organism on this planet that follows the same pattern... a virus. Human beings are a disease, a cancer on this planet; you are a plague, and we... are the cure.” – Agent Smith, in The Matrix.
This is an example of inductive generalization and is a weak argument because Agent Smith is only looking at a sample of the population to make his generalization. The agent has not looked at every human in detail, and not from past to present. Smith takes an idea from a snapshot in time (saying: “during my time here”). So since the ones Smith has observed are a certain way, he states that all humans are like this. Hasty generalization is used as not enough human are observed to create this conclusion.
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77.) Susan must be angry with John because she persistently refuses to talk to him and she goes out her way t avoid him. Even though she used to be his best friend, and even though she still spends a lot of time with his mother, I think she is really annoyed with him right now.
This is a conductive argument, and is rather weak as it uses a slippery slope type of reasoning. It is assumed that Susan must be angry with John when it could be another emotion, or it could be another event that has occurred for her to avoid John. It is not inevitable thAT she won’t talk to him simply because she is angry with him.
78.) We shouldn’t invite J.D. to the picnic. Every time he comes along, it rains.
This is an example of statistical syllogism, and is a weak argument. The argument confuses cause and effect and then implies that J.D.’s presence is what causes rain.
79.) Why have gun control when practically everyone drives a car? After all, cars are just as dangerous as guns.
This is an argument from analogy and assumes that because guns are dangerous and cars are dangerous, and because there are no car control laws, there should be no gun control laws. This argument is not very strong and uses a weak analogy since cars are not at all like guns even if they may both be dangerous. There could also be ignorance of a common cause since it is not stated that people are creating the danger and not the objects themselves.
80.) A recent study shows that in the past ten years, during which time sex education classes have been taught in the high school, there has been a dramatic increase in the number of teens who have contracted venereal disease. The conclusion is obvious: if we want to reduce the number of incidence of venereal disease among our young people, we must get rid of those sex education classes.
This is an example of causal argument that uses post hoc fallacy to get to a conclusion. The argument assumes that sex education classes are the cause regardless of coincidence, such as general increase in population or shifts of cultural norms, etc. This is a weak argument.
81.) Carl and Louise will both be single again soon. After all, they got married in Las Vegas, and most marriages that begin in Las Vegas end in divorce.
This argument uses statistical syllogism to get to a conclusion, and is a weak argument. This argument uses hasty generalization as not enough statistics is observed and not all that are observed results in the stated conclusion of Carl and Louise becoming single again.
82.) Did you notice at the party last night that, as soon as Kevin and Paula arrived, she told him not to drink too much, and then Kevin proceeded to get really drunk? That always seems to happen when they are at a party together: she always complains about his drinking, and he always gets drunk. If she would shut up about it, he probably wouldn’t get drunk at all.
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This is example of a causal argument and is not very weak, though could be true with some level of probability. The argument does confuse cause and effect, assuming that Kevin only drinks because Paula tells him not to and complains about his drinking. In some effect the argument also ignores a common cause that could result in Kevin’s drinking such as other friends urging him to drink, or using drinking to overcome fears of social settings, etc.
83.) No one objects to a psychiatrist’s looking up information in the DSM (Diagnostic and Statistical Manual of Mental of Disorders) to help him or her make a difficult diagnosis. Why, then, shouldn’t students taking a difficult examination be permitted to use their textbooks?
This is an argument of analogy and assumes that psychiatrists looking up information is similar to students looking up information in exams; then concludes that the outcome should be similar. This is a weak analogy and a weak argument, since the situation of psychiatrists who have already conducted their exams without use of textbooks is different than students who have no knowledge in the field.
84.) The solution to the problem of poverty in the United States is obvious. People who live below the poverty line normally have very little education: more than half have less than a grade eight education. Therefore, the way to overcome poverty is to provide incentives and encouragement for poor people to go back to school to complete their education.
This is an example of inductive generalization, and takes a sample of poor people to represent all in poverty and uses the reason for their poverty as that of the whole. This is not a weak argument, but it does use hasty generalization and also slippery slope reasoning. Not enough reasons are observed as to why people are below the poverty line that may not be linked to education and could be due to other causes such as economic slump. The argument also assumes if incentives are provided for school then poor people will advance which may not be inevitable.
85.) All of my students who have taken my critical thinking class have improved their reasoning skills, so I bet any DePaul student who takes my class will improve their reasoning skills.
This argument uses statistical syllogism to get to a conclusion. The argument uses post hoc fallacy in assuming that due to the critical thinking classes, students’ reasoning skills improved. The argument is not completely sound.
86.) Drinking tea on a regular basis will help reduce your risk of a stroke. According to an experiment conducted by the National Research Institute in the Netherlands, men who drank 4 ½ cups of tea a day had a 70% reduced risk of stroke compared to men who had none.
This argument uses inductive reasoning to form a conclusion. The sample of the population is used to represent the whole. The argument is weak, and uses a biased sample for conclusion. It assumes that everyone’s risk of stroke is reduced, when only 70% of the observed had reduction in risk, and the sample population consisted only of men, and then only those from the Netherlands.
87.) How do I know that drinking ginseng tea is a cure for the common cold? Last week I had a bad case of the sniffles. I drank a cup of ginseng tea, and the next morning my sniffles were gone.
This is an example of causal argument and assumes that the sniffles were gone due drinking ginseng tea. This argument is weak and uses post hoc fallacy to get to the conclusion that is by itself, questionable. The argument does not rely on repeated measurements or trials and confuses coincidence of drinking the ginseng tea as being the cure when it could have been the time itself that was the cure as she was ill for a week which is usually the duration of common cold infection.
88.) During the past two months, every time that the cheerleaders have worn blue ribbons in their hair, the basketball team has been defeated. So, to prevent defeats in the future, the cheerleaders should get rid of those blue ribbons.
This argument uses statistical syllogism to make a conclusion that blue ribbons worn by the cheerleaders result in the team’s losses. The argument is weak and confuses cause and effect to make the statement, assuming that because blue ribbons and team losses regularly occur together, then it is because of the ribbons why the team loses.
89.) Smoking cigarettes is just like ingesting arsenic into your system. Both have been shown to be causally related to death. So if you don’t want to take a spoonful of arsenic, I would think that you wouldn’t want to continue smoking.
This is an example of a causal argument and is quite strong in that the conclusion is true on some level of probability. The argument does use hasty generalization however, in assuming that they will both result in death. There are people who smoke that do not die, and there are safe levels of arsenic that can be ingested, therefore one is not exactly similar to the other.
90.) Dexter is a dog, and 94% of all dogs weigh less than 130ibs. Therefore, Dexter probably weighs less than 130ibs.
This argument is an example of inductive generalization as a sample of the population is used to represent the majority, including Dexter. This argument can be considered strong since all dogs were observed and a very high percentage (94%) weighs less than 130lbs.
91.) Sex is just as natural as eating. And just as we don’t regard an appetite for variety in diet as strange or unnatural, why should we consider any less normal a desire for a variety of lovers?
This is an argument of analogy, and assumes that sex and food are similar to some degree, and therefore similar in other degrees. The argument is a weak analogy and also uses hasty generalization to make a conclusion. There is no thought that the consequences in overindulgence of either can be different, or the cultural norms that may cause difference in perception for each activity.
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92.) Very few DePaul students voted for Mitt Romney, and Jane is a student at DePaul, so Jane probably didn’t vote for Mitt Romney.
This is an example of a conductive argument and assumes that Jane is not in the minority. This argument is weak and uses a hast generalization to conclude that Jane did not vote for Mitt Romney simply because most students at her school did not.
93.) You’ve all heard of grade inflation. Well, I want to speak to you about grade depression: the serious harm we do to students by grading them too hard rather than too easily. What does it do to students to measure them by too strict a standard? It frustrates them. It conditions them to expect failure. They recoil from responsibility, always taking the easy route rather than learning to challenge and hence improve themselves. They develop habits of dependency, and many develop other psychological disorders. Can we afford a generation of weak, dependent people unsuited for the demands of contemporary society?
This is a causal argument and supposes that students becoming weak, dependent, and having psychological orders will be because of harsh grading. This is a weak argument and confuses cause and effect where there may be no true correlation. There may be other factors that are not accepted within this argument as contributing to students exhibiting these characteristics. There could also be examples of students finding the strength to push themselves when they receive bad marks because they want to do better, which is not taken into account with this argument.
94.) After only one year the alternator went out for Mr. O Grady’s new Chevrolet. Mrs. Dodson’s Oldsmobile developed a transmission problem after only six months. It’s obvious that cars made by General Motors are a pile of junk these days.
This is an argument from analogy and assumes that all General Motors cars are junk because of two known examples. This argument is weak, and uses hasty generalization to reach a conclusion.
95.) A college education is like the foundation of a house. Both must be solid and adequate to support what will rest on it. And just as you’d not think of laying a foundation without regard to the structure it must support, you should not commence a formal education without knowing what it is you want to do with your life.
This is an example of an argument from analogy, inferring that a college education is much like the foundation of a house. This is a strong analysis, and both are important to living and the future, such that the analysis can be carried through.
You may choose to answer any three questions that you omitted (worth 2 points each)
PART IV – Non-deductive Arguments
96.) Of the four most popular television dramas, two were created by gay men. Marc Cherry is creator of Desperate Housewives, and Ryan Murphy, who is also gay, is the creator of Nip/Tuck. That just goes to show that gay men are more sensitive and talented when it comes to portraying what people want to see in relationships.
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This is an example of inductive generalization, and uses two examples to represent the entire population. This is a weak analysis as individual perception is not accounted for when assessing the sensitivity or level of talent for writing these shows. The sample size used also creates weak analysis. This argument uses a biased sample to show a conclusion, as two cannot represent the whole, and it is possible the whole does not want to be represented as such.
97.) Why does a family who has no children in a school district have to pay school taxes? This is like paying cigarette taxes even though you don’t smoke.
This is an example of conductive argument and one premise does not necessarily link to the other. The analogy could be stronger but uses a slippery slope type of argument to make a conclusion.
98.) Medieval villager: “Two days after that old hag Jezebel Taylor moved into the village, several of my cows died and my crops withered. That witch must have put a hex on me!
This is an example of causal argument, and is a very weak argument. By using post hoc fallacy, the argument assumes that because the crows died around the time Jezebel moved into the village it must have been caused by her. The argument confuses coincidence with the cause.