Critical Thinking: Reason and Evidence D265 Flashcards
Propositions
Statements that can be true or false.
Non-propositions
Sentences that are not statements about matters of fact (or fiction). They do not make a claim that can be true or false.
Which sentence is a non-proposition?
- If the burglar did not go out the front door, they must have gone out a window.
- The earth is the third planet from the sun.
- Where are the keys to my car?
- Mount Everest is the tallest mountain in the world.
Where are the keys to my car?
Did the company really close that deal? It has had a great year. Where is the president right now? Let’s go ask whether the deal was closed.
In the above paragraph, which sentence expresses a proposition?
- Where is the president right now?
- Did the company really close that deal?
- Let’s go ask whether the deal was closed.
- It has had a great year.
It has had a great year.
Simple proposition
Simple propositions have no internal logical structure, meaning whether they are true or false does not depend on whether part of them is true or false. They are simply true or false on their own.
Complex propositions
Complex propositions have internal logical structure, meaning they are composed of simple propositions. Whether they are true or false depends on whether their parts are true or false.
Which sentence expresses a complex proposition?
- Birthday parties can be really fun.
- The cat ate the food, but did not like it.
- Too many employees are used to high-stress work environments in the United States.
- Why did the monkey escape, and who is responsible?
The cat ate the food, but did not like it.
If the computer is not fixed, then the company either needs to buy a new one or will not be able to keep up productivity.
Which of the following breaks down the complex proposition above into the simple propositions?
- If the computer is not fixed, then the company needs to buy a new one. The company will not be able to keep up productivity.
- The computer is not fixed. The company needs to buy a new computer. The company will not be able to keep up productivity.
- The computer is not fixed. The company either needs to buy a new one or will not be able to keep up productivity.
- The company does not have enough computers.
The computer is not fixed. The company needs to buy a new computer. The company will not be able to keep up productivity.
If the new employee wants to succeed, then they need to show up on time. How many times have we heard the manager complain about tardiness? Nobody likes a 7 a.m. start time, but it was in the job description. We should remind the new employee how important this is.
Which is a simple proposition that is expressed in the above paragraph?
- The new employee wants to succeed.
- How many times have we heard the manager complain about tardiness?
- The employees look out for each other.
- If the new employee wants to succeed, then they need to show up on time.
The new employee wants to succeed.
The U.S. healthcare system is difficult to navigate, and this negatively affects many of us. Many people are unsure exactly how their health insurance coverage works and are not sure where they can go to get care. What can be done to improve this? If changes are not made soon, the problem will only get worse.
Which is a simple proposition that is expressed in the above paragraph?
- Many people are not sure where they can go to get care.
- The U.S. healthcare system is difficult to navigate, and this negatively affects many of us.
- What can be done to improve this?
- Many people are unsure exactly how their health insurance coverage works and are not sure where they can go to get care.
Many people are not sure where they can go to get care.
Bad inferential structure
Every argument with the same structure as this argument is bad (invalid or weak). The premises do not, in fact, demonstrate or maybe even support the conclusion. In other words, we can accept the premises as true without being compelled to accept the conclusion. There is something wrong with this argument’s general structure.
False premise
This particular argument has a premise/assumption that is false. There is something wrong with this argument’s particular content.
Conclusion Indicators
Therefore, so, it follows that, hence, thus, entails that, we may conclude that, implies that, wherefore, as a result
Premise Indicators
Because, for, given that, in that, as, since, as indicated by
“Since we cannot go out until the restaurant opens, and given that we are trying to save money, we should just hang out here until closer to dinner.”
Which statements are the premises of the following argument? Choose 2 answers.
- We cannot go out until the restaurant opens.
- We are trying to save money.
- We should just hang out here until closer to dinner.
- We can have a good time without spending money.
- We cannot go out until the restaurant opens.
- We are trying to save money.
Most students in the class scored less than 70% on the exam. This means that the exam was too difficult to accurately assess student learning. Therefore, as exams are supposed to accurately assess student learning, the exam must be revised and readministered.
Which statement is the conclusion of the above argument?
- The exam must be revised and readministered.
- Some students in the class scored higher than 70% on the exam.
- Exams are supposed to accurately assess student learning.
- Most students in the class scored less than 70% on the exam.
The exam must be revised and readministered
Which sentences are arguments? Choose 2 answers.
- We know the student cheated on the exam because the instructor caught the student stealing glances at their neighbor’s test.
- The student only cheated on the exam because their financial aid depended on it.
- No one has ever been to the moon, so we do not know that it is not made of cheese.
- If you suspect you have been infected with rabies, then you should contact a medical professional immediately.
- We know the student cheated on the exam because the instructor caught the student stealing glances at their neighbor’s test.
- No one has ever been to the moon, so we do not know that it is not made of cheese.
Which pairs of sentences are arguments? Choose 2 answers.
- Every time I walk by here, Chris is doing nothing. Chris must not do anything with the available time.
- We need to act now to reverse greenhouse gas emissions. If we do not, the earth will soon become inhospitable to human life.
- John Lennon was shot and killed. So were Bobby Kennedy and his brother John.
- One student cheated on the test. But it was only because the student felt ill prepared.
- Every time I walk by here, Chris is doing nothing. Chris must not do anything with the available time.
- We need to act now to reverse greenhouse gas emissions. If we do not, the earth will soon become inhospitable to human life.
I just heard the news about Riley’s car. It was vandalized last Saturday. There is no doubt Jordan did it. I went to the bowling alley that night. I bowled a 160! Anyway, I saw Jordan there and, although it was barely noticeable, I definitely saw paint on Jordan’s shirt. It is unlikely there would be paint on Jordan’s shirt unless Jordan had spray-painted Riley’s car. It is a shame, really, since it was such a nice shirt. It was the green one. Oh, and you know Jordan has motive. After all, Jordan has a well-known grudge against Riley. You remember when Riley borrowed Jordan’s lawnmower and did not return it. And there was opportunity, because Jordan does not work on the weekend and usually stays home watching television. But the lightning storm earlier last week short-circuited Jordan’s TV set. Besides, they canceled Jordan’s favorite Saturday evening show.
Which description best characterizes the above?
- A story
- An argument
An argument
Kinds of Inferences
Deduction
Induction
Inference to the best explanation or abduction
Deduction
arguments where the premises guarantee or necessitate the conclusion
— mathematical arguments, logical arguments, arguments from definition
Induction
arguments where the premises make the conclusion probable
— analogies, authority, causal inferences, scientific reasoning, extrapolations, etc.
Inference to the best explanation or abduction
arguments where the best available explanation is chosen as the correct explanation
Truth
A true proposition accurately represents reality.