Show:
Week 1 Material
Week 2 Material
Week 3 Material
Week 4 Material
Wild Card
100
True or false: The conclusion of an argument will always be at the end of the passage.
False: The conclusion can be in any part of the passage---this is why it's important to look for conclusion indicator words and to employ the recombination test when necessary. In your own arguments, it's best to be explicit about what your conclusion is, so there's no confusion.
100
Is the following argument logically valid? "If you study 100 hours, then you will get an A on the final. You got an A on the final. So, you studied for 100 hours."
No: This is an instance of affirming the consequent, which is a logical fallacy---it is possible that you got an A while studying a much healthier amount of hours for the final.
100
True or false: The presence of a correlation between two things implies a causal relationship between those two things.
False: Although correlations can be a general sign of causation, it does not imply (= entail) causation by itself. Sometimes correlations can be due to chance. Sometimes they can be due to some third factor.
100
True or false: "X is a T-Rex" is a sufficient condition for "X is a dinosaur"?
True: If X is a T-Rex, then we have enough to know that X is a dinosaur. (But of course, that is not a necessary condition, as something can be a dinosaur without being a T-Rex.)
100
True or false: A good definition cannot be subject to any counterexamples.
True: If a definition is subject to even one counterexample, then it shows that the definition does not capture the concept exactly. (Of course, it may be the case that the definition can be revised in response in a way that avoids the counterexample.)
200
True or false: In a deductive argument, if the premises are true, then the conclusion *must* be true as well.
True: This is the definition of a deductive argument. (But of course, the premises of a deductive argument can be false, in which case the argument is unsound.)
200
What deductive rule does the following argument employ? "Either Hillary Clinton or Donald Trump will be the next US president. If Clinton wins, then the next president will be an American citizen. And if Trump wins, then the next president will be an American citizen. So, the next president will be an American citizen.
This argument is a dilemma. Notice that if both sides of a dilemma have the same consequence, then the main conclusion will just be that consequence (in that case, it need not be in an either-or form).
200
True or false: If a comparison between X and Y is faulty for conclusion P, then a comparison will between X and Y will also be faulty for conclusion Q.
False: The strength of the similarities between two things for an argument by analogy depends heavily on what the context of the argument is, and this in turn depends on what the conclusion of the argument is.
200
Provide a necessary, but not sufficient condition, for "X tells a lie."
Sample answer: "X says something that is not completely true." You can't tell a lie without saying something that is not completely true, so this is a necessary condition. But that by itself is insufficient for telling a lie---its presence by itself does not guarantee that a lie is there---as you might tell something not completely true while believing that it is completely true. That would not be a lie.
200
Give an example of a conditional and an example of a disjunction.
A conditional is a sentence that can be put into an if-then form. So an example would be, "If Clinton becomes the next president, then the next president will be a Democrat." A disjunction is a statement that can be put into either-or form. So an example would be, "Either Hillary Clinton or Donald Trump will be the next president.
300
Is the following argument deductive or nondeductive? "There is only a 0.1% chance that your lottery ticket will win the Powerball. What I'm saying is, you won't win."
Nondeductive: The premise in the first sentence only makes the conclusion probable. It is *possible* that the premise is true and the conclusion is false.
300
True or false: If an argument is logically valid, then it is sound.
False: If the argument has a false premise, then it will be unsound even though it is valid.
300
Which abductive criteria looks for whether or not a theory is consistent with experts in a field believe to be true?
The coherence criteria. Notice that this is not an absolute requirement---new theories almost always do poorly on this criteria, but can overcome it by excelling on the other three criteria.
300
After Sarah argued that the Patriot Act violates some basic human rights, John responded, "Basically, Sarah's saying that she doesn't care if more terrorist attacks happen, an obviously terrible position." What informal fallacy has John committed?
The straw-man: he has caricatured Sarah's argument into a much weaker form, and he's pretended that a criticism of the weak argument shows that the stronger argument is also flawed.
300
Air Bud the dog misses a free throw. A few seconds later, he hears a very loud clap of thunder. Air Bud gets scared that his missing a free throw caused the loud thunderclap. What mistake in causal reasoning did Air Bud make?
Air Bud made the "after this, therefore because of this" fallacy (also called the post-hoc informal fallacy)---from the mere fact that one thing (the thunderclap) came after the other (missing the free throw), Air Bud concluded that first thing was caused by the second. (It's okay, Air Bud!)
400
Is the following argument deductive or nondeductive? "If a six-sided die is rolled, then it has a 83.3% chance of not landing on six. If there is an 83.3% chance that the die does not land on six, then it is more likely than not that the die does not land on six. So, if a six-sided die is rolled, then it is more likely than not that the die does not land on six."
Deductive: Even though the argument involves probabilities, if you look at the structure of the premises (if p, then q; if q then r; so if p then r), it is an instance of hypothetical syllogism, which is a deductive inference.
400
What deductive rule does the following argument employ. "If Lydia's program always wins a game of chess, then if the program played a duplicate of itself, both programs would win. But there can only be one winner in a game of chess. So, Lydia's program does not *always* win a game of chess."
This is a reductio ad absurdum. The key sign is that it reaches a contradiction (both programs would win, but only one program can win a game of chess), which only reductios intend to establish.
400
Consider two theories about JFK's assassination. The one-shooter theory says that only one shooter was responsible. The two-shooter theory says that two shooters were responsible. Both theories do equally well when it comes to the ______ requirement of abduction, but the two-shooter theory does worse when it comes to the _____ requirement.
The first blank should be "comprehensiveness in scope"---both theories, if true, would explain how JFK died. The second blank could be either "coherence" (most experts do not believe that there were two shooters) or "simplicity" (the theory invokes more shooters than is needed to explain the evidence of JFK's death).
400
When asked if his proposed jobs bills would actually cause the economy more bad than good, Charles Logan responded, "Since I've been in office, the economy has never been better!" What informal fallacy has Logan committed?
Red herring: whether or not the economy has never been better does not tell us one way or the other whether *this specific bill* would help or harm the economy. It is irrelevant to that issue, which makes it red herring as it distracts the reader from the issue at hand.
400
True or false: Affirming the consequent is not an informal fallacy.
True: Affirming the consequent is a logical fallacy---its fallacy relates to its logical form (if p, then q; q; so, p). *Informal* fallacies aren't like that---whether or not a sentence of the form "most X think Y, so Y is probably true" is true depends on the content of X and Y, not the form.
500
Assuming the following argument is a deductively valid argument, fill in the implicit premise. "Either Michael Gove, Andrea Leadsome, or Theresa May will be Britain's next prime minister. But Michael Gove won't be the next prime minister, since he lost the most recent vote. So, Theresa May will be the next prime minister."
The implicit premise will have the form "Andrea Leadsome won't be Britain's next prime minister." The structure of the argument (start with a disjunction, and eliminate some of the options) is a tip-off that we're dealing with a use of disjunctive syllogism. To conclude that May will be the next prime minister we have to eliminate the other options. The argument only explicitly eliminates Gove, so it has an implicit premise eliminating Leadsome.
500
Two deductive rules are employed in the following argument. Which two? "If there was a coup in Turkey, then either President Erdogan knew about it or was ignorant about it. There was in fact a coup in Turkey. So, either Erdogan knew about it or he was ignorant about it. Erdogan couldn't be ignorant about something like that. So, he knew about it."
Modus ponens, and then disjunctive syllogism. The first sentence is a conditional (it's in if-then form), so that narrows that rule applies. The second sentence and the subconclusion in the third sentence help us to fill in the blank: the second sentence affirms the antecedent of the conditional, and the subconclusion establishes the consequent of the conditional. So, the first rule used is modus ponens. At that subconclusion, we end up with an either-or sentence. We then eliminate one of the options to prove the other, which is our sign that the second rule used is disjunctive syllogism.
500
Suppose that Brandon wears his Broncos shirt for every one of their games, and they have a good season---they win 15 games and lose 4. From this, he concludes that wearing his Broncos shirt causes his team to win. Does Brandon's conclusion pass Mill's Method of Agreement? Does it pass Mill's Method of Difference?
It passes the Method of Agreement: whenever the supposed effect (the Broncos winning) is there, the supposed cause is there (Brandon wears his Broncos shirt). But it does not pass the Method of Difference: it's not true that whenever the suppose effect is absent, the supposed cause is also absent---even when the Broncos lost, Brandon still wears his shirt. This is a sign that Brandon's wearing his shirt does not make the difference between the Broncos' winning and losing.
500
Provide a counterexample to the following definition. "X is a freshman at UCR =df. X is 18 years old and goes to school in Riverside."
Sample answer: There are 18 year old students who go to RCC, which is in Riverside, but are not students at UCR. This shows that the definition is too broad: it counts people as UCR students who actually are not. (Conversely, there are freshmen at UCR who are older or younger than 18. This shows that the definition is too narrow as well, as it wrongly excludes genuine UCR freshmen.)
500
If an argument is logically invalid, what may we infer about the truth or falsity of its conclusion?
Nothing: If an argument is logically invalid, then all we can say is that the argument fails to prove its conclusion. We have no information one way or the other to tell if the conclusion is true or false.