1. All sound arguments are valid. T 2. An inductively strong argument ...
PHL 214 SAMPLE TEST 2 ANSWERS A) True or False? 1. All sound arguments are valid. T 2. An inductively strong argument may be deductively invalid. T 3. An argument that affirms the consequent is invalid. T 4. Arguments are deductive when they are intended to be valid. T 5. The following argument is invalid: “Roses are red, and daffodils are yellow, and lilies are white. Therefore, flowers are probably coloured.” T 6. The genetic fallacy is a kind of red herring. T 7. In a straw man fallacy, the premises are irrelevant to the conclusion. T B) Multiple Choice 1. An argument: “Sally is a mathematician. If she’s a mathematician, she’s bad at art. So she must be bad at art.” The argument (a) affirms the consequent (b) denies the consequent (c) affirms the antecedent [In the premise “If she’s a mathematician, she’s bad at art”, the antecedent is “Sally is a mathematician”] (d) does none of these things.
2. An argument: “Either you’re Japanese or you’re Catholic, and seeing as you’re clearly not Japanese you must be Catholic.” The argument is (a) a hypothetical syllogism (b) a false dilemma (c) a disjunctive syllogism (d) an instance of denying the consequent (e) both b and c [The disjunctive premise “Either you’re Japanese or you’re Catholic” is obviously untrue; there are all kinds of other possibilities, so it’s a false dilemma. But it has the form of a disjunctive syllogism (and is therefore valid).] (f) a, b and c
(g) None of the above
3. In any hypothetical syllogism, the conclusion and the premises are all (a) true (b) valid (c) both valid and sound (d) conditional statements [The form of the argument is “If A then B; If B then C; therefore, if A then C”.] (e) “or” statements (f) statements that cannot be known to be true, but which appear to be reasonable hypotheses
4. An argument: “If you’re human you’re Canadian. You are Canadian, so you must be human.” The argument is (a) invalid (b) valid (c) an instance of affirming the consequent [The argument affirms the antecedent (i.e., the statement that you’re Canadian) and so it’s invalid. So I should have had “a and c” as a possible answer here.] (d) an instance of affirming the antecedent (e) None of the above
5. If two premises are “independent”, that means that (a) each rationally supports the (same) conclusion on its own (b) each is meant by the arguer to rationally support the (same) conclusion on its own (c) each can be known to be true (or reasonable to believe) independent of the other one (d) each can be known to be true (or reasonable to believe) independent of sensory experience (e) each is intended to be known to be true (or reasonable to believe) independent of the other (f) None of the above
6. One difference between deductive validity and inductive strength is that (a) the conclusion of an inductively strong argument is never certain (b) the conclusion of a deductively valid argument must be true, whereas the conclusion of an inductively strong argument need only be probable (c) if an argument is deductively valid, the premises are intended to make the conclusion 100% certain (d) unlike inductive strength, deductive validity does not come in degrees [Since both c and d describe differences, either of these answers is good. Maybe I should have had “a and d” or “a or d” as a possible answer.] (e) unlike deductive validity, inductive strength has nothing to do with whether the premises of the argument are actually true (f) None of the above
C) Diagrams Draw a diagram to represent the following argument in the space below: “Most people think the lunar landing was real, but in fact it was a big hoax. First of all, consider that it’s physically impossible for human beings to travel more than 100 km from the surface of the earth. (I know, because my uncle told me so.) Moreover, the only evidence we have for the lunar landing is that the American government said it happened; but they lie about everything all the time.” 1: The lunar landing was a big hoax. 2: It’s physically impossible for human beings to travel more than 100 km from the surface of the earth. 3: My uncle told me that it’s physically impossible for human beings to travel more than 100 km from the surface of the earth. 4: The only evidence we have for the lunar landing is that the American government said it happened. 5: The American government lies about everything all the time. I can’t figure out how to make a diagram on this word processor. You figure it out – a good exercise. The diagram should be as follows: Conclusion = statement 1. There are two subordinate arguments here, each meant to support 1. Here is one argument: statement 2 is a premise leading to 1, and statement 2 is itself supported by 3 (i.e., 2 is a subordinate conclusion). Another subordinate argument has two dependent premises: 4
and 5 are dependent premises leading to 1. (The claim that the only evidence comes from the government, together with the claim that the government lies all the time, is meant to support the conclusion that the lunar landing was a big hoax.)
D) Identifying Fallacies For each of the following passages, state (a) whether there is a fallacy, (b) which kind of fallacy is committed (if there is one), and (c) how that fallacy is exemplified in the passage. 1. Rob Ford is obviously homophobic, so we should not listen to his argument about cutting funding for the Gay Pride Parade. APPEAL TO THE PERSON (OR, MORE PRECISELY, CIRCUMSTANTIAL AD HOMINEM). THE ARGUER ATTEMPTS TO DISMISS FORD’S ARGUMENT ON THE BASIS OF AN IRRELEVANT FACT ABOUT FORD’S PERSONALITY OR BELIEFS (OR “CIRCUMSTANCES”). THE FACT THAT FORD IS HOMOPHOBIC IS NOT RELEVANT TO THE QUESTION OF WHETHER HIS ARGUMENT ABOUT THE GAY PRIDE PARADE IS A GOOD ARGUMENT, WHETHER ITS CONCLUSION IS TRUE, ETC. 2. Rob Ford is known to have lied to the public on many occasions. We shouldn’t believe him when he says he didn’t smoke crack. (For all we know, that might be another lie.) THIS IS NOT A FALLACY. THE PREMISE THAT FORD HAS LIED TO THE PUBLIC MANY TIMES BEFORE IS CERTAINLY RELEVANT TO THE CONCLUSION; IT GIVES US A GOOD REASON FOR SKEPTICISM ABOUT HIS CLAIM. (NOTICE THAT IT WOULD BE A FALLACY IF INSTEAD THE CONCLUSION WERE THAT FORD’S CLAIM MUST BE FALSE, THAT HE REALLY DID SMOKE CRACK, ETC.) 3. Either you agree with us that Rob Ford should step down or you’re one of those nasty, prejudiced dummies who think Rob Ford is the greatest human being who ever lived. Seeing as you apparently don’t agree that he should step down, I conclude you must be one of those people. FALSE DILEMMA, I.E., A DISJUNCTIVE SYLLOGISM WITH AN OBVIOUSLY FALSE DISJUNCTIVE PREMISE. THE DISJUNCTIVE PREMISE IS: “EITHER YOU AGREE WITH US THAT ROB FORD SHOULD STEP DOWN OR YOU’RE ONE OF THOSE NASTY, PREJUDICED DUMMIES WHO THINK ROB FORD IS THE GREATEST HUMAN BEING WHO EVER LIVED”. THIS IS OBVIOUSLY FALSE, BECAUSE THERE ARE OBVIOUSLY OTHER POSSIBILITIES THAT THE ARGUER OVERLOOKS – E.G., YOU MIGHT THINK ROB FORD IS NOT A VERY GOOD MAYOR, AND NOT AN ESPECIALLY GREAT PERSON, BUT ALSO THINK THAT HE IS NOT SUCH A BAD MAYOR THAT HE SHOULD STEP DOWN, ETC. SO WHILE THE PREMISE IS RELEVANT TO THE CONCLUSION IT’S UNACCEPTABLE. 4. There’s no evidence that Rob Ford smokes crack. So he doesn’t. These allegations are just silly. APPEAL TO IGNORANCE. THE ARGUER CLAIMS THAT FORD DOES NOT SMOKE CRACK ON THE GROUNDS THAT THERE’S NO EVIDENCE HE DOES NOT. THE PREMISE IS IRRELEVANT TO THE CONCLUSION. EVEN IF FORD DID SMOKE CRACK, THERE’S NO REASON TO ASSUME THAT WE’D BE LIKELY TO HAVE EVIDENCE OF THAT FACT; SO THE
FACT THAT THERE IS NO SUCH EVIDENCE TELLS US NOTHING ABOUT THE QUESTION OF WHETHER HE SMOKES CRACK. 5. Eugenics is evil and wrong. Do you know who believed in eugenics? Nazis and other fascists, that’s who. The whole idea comes from fascist ideology and the evil belief that some people are naturally better than others. GENETIC FALLACY: THE ARGUER ATTEMPTS TO DISCREDIT EUGENICS ON THE IRRELEVANT GROUND THAT NAZIS AND OTHER FASCISTS BELIEVED IN EUGENICS. SO THE PREMISE HAS TO DO WITH THE (SUPPOSED) ORIGINS OF EUGENIC THEORIES, WHEN THE ORIGIN HAS NOTHING TO DO WITH THE ARGUMENT’S CONCLUSION. 6. It’s wrong to eat meat. Everyone in our community has been a strict vegetarian for the last two hundred years. APPEAL TO TRADITION/APPEAL TO COMMON PRACTICE: THE ARGUER DRAWS THE CONCLUSION THAT IT’S WRONG TO EAT MEAT FROM AN IRRELEVANT PREMISE ABOUT WHAT IS TRADITIONALLY BELIEVED OR HOW PEOPLE TRADITIONALLY BEHAVE IN HER COMMUNITY. PERHAPS THE MORE PLAUSIBLE DIAGNOSIS IS APPEAL TO COMMON PRACTICE. THIS IS IRRELEVANT, BECAUSE THE MERE FACT THAT THESE PEOPLE HAVE ALWAYS BEHAVED IN THIS WAY – BY BEING VEGETARIAN – IS NO REASON TO SUPPOSE THAT THEIR PRACTICE IS MORALLY RIGHT OR REASONABLE.) 7. Socialism is a crazy idea. It’s just crazy to believe that our economy can function when no one does any productive work and everyone just sits around taking money from the government for doing nothing. STRAW MAN: THE ARGUER ATTACKS THE IDEA THAT “OUR ECONOMY CAN FUNCTION WHEN NO ONE DOES ANY PRODUCTIVE WORK” (ETC) AS IF THIS WERE A GOOD DEFINITION OR DESCRIPTION OF “SOCIALISM”. BUT MANY FORMS OF SOCIALISM ARE CLEARLY NOT EQUIVALENT TO THIS SILLY IDEA. SO THE ARGUER IS CONCLUDING THAT SOCIALISM IS “CRAZY” ON THE BASIS OF A DISTORTION OF THE THEORY THAT MAKES IT EASIER TO ATTACK. THE PREMISES OF THE ARGUMENT ARE THEREFORE IRRELEVANT (BECAUSE THE IDEA THAT IS BEING DISCREDITED IS NOT THE ONE MENTIONED IN THE CONCLUSION). 8. Know what I think? Philosophy is bad for your mental health. If you question common sense beliefs, you’ll start to believe in crazy conspiracy theories, and if you believe in conspiracy theories you’ll become totally paranoid about everything. Pretty soon you’ll be hiding in a closet with a tin foil hat in the hope of protecting yourself from the CIA’s mind control programs. SLIPPERY SLOPE FALLACY: THE ARGUER CLAIMS THAT DOING QUESTIONING COMMON SENSE LEADS TO BELIEVING IN CONSPIRACY THEORIES, THAT THIS IN TURN LEADS TO BEING “TOTALLY PARANOID ABOUT EVERYTHING”. THOUGH THE PREMISES ARE RELEVANT, THEY ARE NOT ACCEPTABLE: THE ARGUMENT IS ESSENTIALLY A HYPOTHETICAL SYLLOGISM WITH OBVIOUSLY UNTRUE CONDITIONAL PREMISES.
2. An argument: “Either you’re Japanese or you’re Catholic, and seeing as you’re clearly not Japanese you must be Catholic.” The argument is (a) a hypothetical syllogism (b) a false dilemma (c) a disjunctive syllogism (d) an instance of denying the consequent (e) both b and c [The disjunctive premise “Either you’re Japanese or you’re Catholic” is obviously untrue; there are all kinds of other possibilities, so it’s a false dilemma. But it has the form of a disjunctive syllogism (and is therefore valid).] (f) a, b and c
(g) None of the above
3. In any hypothetical syllogism, the conclusion and the premises are all (a) true (b) valid (c) both valid and sound (d) conditional statements [The form of the argument is “If A then B; If B then C; therefore, if A then C”.] (e) “or” statements (f) statements that cannot be known to be true, but which appear to be reasonable hypotheses
4. An argument: “If you’re human you’re Canadian. You are Canadian, so you must be human.” The argument is (a) invalid (b) valid (c) an instance of affirming the consequent [The argument affirms the antecedent (i.e., the statement that you’re Canadian) and so it’s invalid. So I should have had “a and c” as a possible answer here.] (d) an instance of affirming the antecedent (e) None of the above
5. If two premises are “independent”, that means that (a) each rationally supports the (same) conclusion on its own (b) each is meant by the arguer to rationally support the (same) conclusion on its own (c) each can be known to be true (or reasonable to believe) independent of the other one (d) each can be known to be true (or reasonable to believe) independent of sensory experience (e) each is intended to be known to be true (or reasonable to believe) independent of the other (f) None of the above
6. One difference between deductive validity and inductive strength is that (a) the conclusion of an inductively strong argument is never certain (b) the conclusion of a deductively valid argument must be true, whereas the conclusion of an inductively strong argument need only be probable (c) if an argument is deductively valid, the premises are intended to make the conclusion 100% certain (d) unlike inductive strength, deductive validity does not come in degrees [Since both c and d describe differences, either of these answers is good. Maybe I should have had “a and d” or “a or d” as a possible answer.] (e) unlike deductive validity, inductive strength has nothing to do with whether the premises of the argument are actually true (f) None of the above
C) Diagrams Draw a diagram to represent the following argument in the space below: “Most people think the lunar landing was real, but in fact it was a big hoax. First of all, consider that it’s physically impossible for human beings to travel more than 100 km from the surface of the earth. (I know, because my uncle told me so.) Moreover, the only evidence we have for the lunar landing is that the American government said it happened; but they lie about everything all the time.” 1: The lunar landing was a big hoax. 2: It’s physically impossible for human beings to travel more than 100 km from the surface of the earth. 3: My uncle told me that it’s physically impossible for human beings to travel more than 100 km from the surface of the earth. 4: The only evidence we have for the lunar landing is that the American government said it happened. 5: The American government lies about everything all the time. I can’t figure out how to make a diagram on this word processor. You figure it out – a good exercise. The diagram should be as follows: Conclusion = statement 1. There are two subordinate arguments here, each meant to support 1. Here is one argument: statement 2 is a premise leading to 1, and statement 2 is itself supported by 3 (i.e., 2 is a subordinate conclusion). Another subordinate argument has two dependent premises: 4
and 5 are dependent premises leading to 1. (The claim that the only evidence comes from the government, together with the claim that the government lies all the time, is meant to support the conclusion that the lunar landing was a big hoax.)
D) Identifying Fallacies For each of the following passages, state (a) whether there is a fallacy, (b) which kind of fallacy is committed (if there is one), and (c) how that fallacy is exemplified in the passage. 1. Rob Ford is obviously homophobic, so we should not listen to his argument about cutting funding for the Gay Pride Parade. APPEAL TO THE PERSON (OR, MORE PRECISELY, CIRCUMSTANTIAL AD HOMINEM). THE ARGUER ATTEMPTS TO DISMISS FORD’S ARGUMENT ON THE BASIS OF AN IRRELEVANT FACT ABOUT FORD’S PERSONALITY OR BELIEFS (OR “CIRCUMSTANCES”). THE FACT THAT FORD IS HOMOPHOBIC IS NOT RELEVANT TO THE QUESTION OF WHETHER HIS ARGUMENT ABOUT THE GAY PRIDE PARADE IS A GOOD ARGUMENT, WHETHER ITS CONCLUSION IS TRUE, ETC. 2. Rob Ford is known to have lied to the public on many occasions. We shouldn’t believe him when he says he didn’t smoke crack. (For all we know, that might be another lie.) THIS IS NOT A FALLACY. THE PREMISE THAT FORD HAS LIED TO THE PUBLIC MANY TIMES BEFORE IS CERTAINLY RELEVANT TO THE CONCLUSION; IT GIVES US A GOOD REASON FOR SKEPTICISM ABOUT HIS CLAIM. (NOTICE THAT IT WOULD BE A FALLACY IF INSTEAD THE CONCLUSION WERE THAT FORD’S CLAIM MUST BE FALSE, THAT HE REALLY DID SMOKE CRACK, ETC.) 3. Either you agree with us that Rob Ford should step down or you’re one of those nasty, prejudiced dummies who think Rob Ford is the greatest human being who ever lived. Seeing as you apparently don’t agree that he should step down, I conclude you must be one of those people. FALSE DILEMMA, I.E., A DISJUNCTIVE SYLLOGISM WITH AN OBVIOUSLY FALSE DISJUNCTIVE PREMISE. THE DISJUNCTIVE PREMISE IS: “EITHER YOU AGREE WITH US THAT ROB FORD SHOULD STEP DOWN OR YOU’RE ONE OF THOSE NASTY, PREJUDICED DUMMIES WHO THINK ROB FORD IS THE GREATEST HUMAN BEING WHO EVER LIVED”. THIS IS OBVIOUSLY FALSE, BECAUSE THERE ARE OBVIOUSLY OTHER POSSIBILITIES THAT THE ARGUER OVERLOOKS – E.G., YOU MIGHT THINK ROB FORD IS NOT A VERY GOOD MAYOR, AND NOT AN ESPECIALLY GREAT PERSON, BUT ALSO THINK THAT HE IS NOT SUCH A BAD MAYOR THAT HE SHOULD STEP DOWN, ETC. SO WHILE THE PREMISE IS RELEVANT TO THE CONCLUSION IT’S UNACCEPTABLE. 4. There’s no evidence that Rob Ford smokes crack. So he doesn’t. These allegations are just silly. APPEAL TO IGNORANCE. THE ARGUER CLAIMS THAT FORD DOES NOT SMOKE CRACK ON THE GROUNDS THAT THERE’S NO EVIDENCE HE DOES NOT. THE PREMISE IS IRRELEVANT TO THE CONCLUSION. EVEN IF FORD DID SMOKE CRACK, THERE’S NO REASON TO ASSUME THAT WE’D BE LIKELY TO HAVE EVIDENCE OF THAT FACT; SO THE
FACT THAT THERE IS NO SUCH EVIDENCE TELLS US NOTHING ABOUT THE QUESTION OF WHETHER HE SMOKES CRACK. 5. Eugenics is evil and wrong. Do you know who believed in eugenics? Nazis and other fascists, that’s who. The whole idea comes from fascist ideology and the evil belief that some people are naturally better than others. GENETIC FALLACY: THE ARGUER ATTEMPTS TO DISCREDIT EUGENICS ON THE IRRELEVANT GROUND THAT NAZIS AND OTHER FASCISTS BELIEVED IN EUGENICS. SO THE PREMISE HAS TO DO WITH THE (SUPPOSED) ORIGINS OF EUGENIC THEORIES, WHEN THE ORIGIN HAS NOTHING TO DO WITH THE ARGUMENT’S CONCLUSION. 6. It’s wrong to eat meat. Everyone in our community has been a strict vegetarian for the last two hundred years. APPEAL TO TRADITION/APPEAL TO COMMON PRACTICE: THE ARGUER DRAWS THE CONCLUSION THAT IT’S WRONG TO EAT MEAT FROM AN IRRELEVANT PREMISE ABOUT WHAT IS TRADITIONALLY BELIEVED OR HOW PEOPLE TRADITIONALLY BEHAVE IN HER COMMUNITY. PERHAPS THE MORE PLAUSIBLE DIAGNOSIS IS APPEAL TO COMMON PRACTICE. THIS IS IRRELEVANT, BECAUSE THE MERE FACT THAT THESE PEOPLE HAVE ALWAYS BEHAVED IN THIS WAY – BY BEING VEGETARIAN – IS NO REASON TO SUPPOSE THAT THEIR PRACTICE IS MORALLY RIGHT OR REASONABLE.) 7. Socialism is a crazy idea. It’s just crazy to believe that our economy can function when no one does any productive work and everyone just sits around taking money from the government for doing nothing. STRAW MAN: THE ARGUER ATTACKS THE IDEA THAT “OUR ECONOMY CAN FUNCTION WHEN NO ONE DOES ANY PRODUCTIVE WORK” (ETC) AS IF THIS WERE A GOOD DEFINITION OR DESCRIPTION OF “SOCIALISM”. BUT MANY FORMS OF SOCIALISM ARE CLEARLY NOT EQUIVALENT TO THIS SILLY IDEA. SO THE ARGUER IS CONCLUDING THAT SOCIALISM IS “CRAZY” ON THE BASIS OF A DISTORTION OF THE THEORY THAT MAKES IT EASIER TO ATTACK. THE PREMISES OF THE ARGUMENT ARE THEREFORE IRRELEVANT (BECAUSE THE IDEA THAT IS BEING DISCREDITED IS NOT THE ONE MENTIONED IN THE CONCLUSION). 8. Know what I think? Philosophy is bad for your mental health. If you question common sense beliefs, you’ll start to believe in crazy conspiracy theories, and if you believe in conspiracy theories you’ll become totally paranoid about everything. Pretty soon you’ll be hiding in a closet with a tin foil hat in the hope of protecting yourself from the CIA’s mind control programs. SLIPPERY SLOPE FALLACY: THE ARGUER CLAIMS THAT DOING QUESTIONING COMMON SENSE LEADS TO BELIEVING IN CONSPIRACY THEORIES, THAT THIS IN TURN LEADS TO BEING “TOTALLY PARANOID ABOUT EVERYTHING”. THOUGH THE PREMISES ARE RELEVANT, THEY ARE NOT ACCEPTABLE: THE ARGUMENT IS ESSENTIALLY A HYPOTHETICAL SYLLOGISM WITH OBVIOUSLY UNTRUE CONDITIONAL PREMISES.
