Logic-Quiz 1

Complex Question Fallacy

(Presumption Fallacy)When did you stop beating your wife? Question embeds a loaded assumption, where no matter how the respondent replies, they are admitting/agreeing to something, trap respondent into acknowledging something

inductive or deductive?

1) indicator words 2) strength of link between premises and conclusion 3) the form or style of argumentation

Slippery Slope

A fallacy that assumes that taking a first step will lead to subsequent steps that cannot be prevented, alleged chain reaction and there is not sufficient reason to think that the chain reaction will actually take place

Whoever thrusts a knife into another person should be arrested. But surgeons do precisely this when operating. Therefore, surgeons should be arrested. What kind of fallacy?

Accident- general to specific not covered

The travel brochure states that walking up O'Connell Street, the statue of Parnell comes into view. Apparently that statue has no trouble getting around. Name that Fallacy

Amphiboly because whole first statement is misunderstood

Appeal To Ignorance

Because we can't prove that it is false, it must be true

Difference between red herring, straw man, and missing the point

Both the red herring and straw man fallacies are susceptible of being confused with missing the point, because all three involve a similar kind of irrelevancy. To avoid this confusion, one should note that both red herring and straw man proceed by generating a new set of premises, whereas missing the point does not. Straw man draws a conclusion from new premises that are obtained by distorting an earlier argument, and red herring, if it draws any conclusion at all, draws one from new premises obtained by changing the subject. Missing the point, however, draws a conclusion from the original premises. Also, in the red herring and straw man, the conclusion, if there is one, is relevant to the premises from which it is drawn; but in missing the point, the conclusion is irrelevant to the premises from which it is drawn.

Lenses function by refracting light at their surfaces. Consequently, their action depends not only on the shape of the lens surfaces, but also on the indices of refraction of the lens material and the surrounding medium. What kind of argument?

Deductive, probably arg from definition

On Monday I drank ten rum and Cokes, and the next morning I woke up with a headache. On Wednesday I drank eight gin and Cokes, and the next morning I woke up with a headache. On Friday I drank nine bourbon and Cokes, and the next morning I woke up with a headache. Obviously, to prevent further headaches I must give up Coke.

False Cause

A deductive argument with true premises and a false conclusion is...

INVALID. Typically, knowing the truth values of the statements cannot indicate validity except in this case, where the values show that it is possible to find a counterexample (it is the counterexample) This is also true for inductive arguments! with p=t and c=f, we know the arg is weak

Difference between Red Herring and Straw Man

In the straw man, the arguer begins by distorting an opponent's argument and concludes by knocking down the distorted argument. In the red herring, the arguer ignores the opponent's argument (if there is one) and subtly changes the subject.

World-renowned physicist Stephen Hawking says that the condition of the universe at the instant of the big bang was more highly ordered than it is today. In view of Hawking's stature in the scientific community, we should conclude that this description of the universe is correct. What kind of argument?

Inductive, argument from authority

Paying off terrorists in exchange for hostages is not a wise policy, since such action will only lead them to take more hostages in the future. What kind of argument?

Inductive, casual inference

The Simpson incident had shown me that a dog was kept in the stables, and yet, though someone had been in and had fetched out a horse, he had not barked enough to arouse the two lads in the loft. Obviously the midnight visitor was someone whom the dog knew well. what kind of arg?

Inductive, casual inference

When the Romans occupied England, coal was burned. Since coal produces quite a bit of soot and sulfur dioxide, there must have been days almost 2,000 years ago when the air in the larger towns was badly polluted. what kind of arg?

Inductive, casual inference

Evaluate deductive arg: Since some fruits are green, and some fruits are apples, it follows that some fruits are green apples.

Invalid, unsound; true premises, true conclusion. does not NECESSARILY follow, sub in banana to test form

Mr. Rhodes is suffering from amnesia and has no recollection whatever of the events of the past two weeks. We can only conclude that he did not commit the crime of murdering his wife a week ago, as he has been accused of doing. Name that fallacy

MIssing the point

Evaluate deductive arg: All leopards with lungs are carnivores. Therefore, all leopards are carnivores

Missing a premise so invalid and unsound. true premise and conclusions

Student loan debt is becoming a national crisis. Clearly, we should provide free textbooks to all college students. Name this fallacy

Missing the point

We've all heard the argument that too much television is the reason our students can't read and write. Yet many of today's TV shows are excellent. Madam Secretary offers a look at the personal and professional life of a secretary of state, The Big Bang Theory serves up lots of laughs in a highbrow setting, and The Voice presents vocalists from across the country competing with help from coaches. Today's TV is just great!

Name that fallacy

Cognitive bias: Availability Hueristic

People believe the information most readily available to them ti what is correct. Overestimate the importance of info nearest to them My example:Have you tried washing your face? I used to have really bad acne, but the solution is just to wash your face whenever you sweat, it worked for me.

We've all heard the complaint that millions of Americans are without adequate health care. But America's doctors, nurses, and hospitals are among the best in the world. Thousands of people come from abroad every year to be treated here. Clearly there is nothing wrong with our health-care system. Name that Fallacy

Red Herring because makes new premises

Ellen Quinn has argued that logic is not the most important thing in life. Apparently Ellen advocates irrationality. It has taken two million years for the human race to achieve the position that it has, and Ellen would throw the whole thing into the garbage. What utter nonsense! Name that fallacy

Straw Man

Validity

Suppose the premises to be true, if the conclusion follow necessarily, then it is valid

During the fifty years that Mr. Jones worked, he contributed $90,000 to Social Security. Now that he is retired, he stands to collect $200,000 from the system. Obviously he will collect a much greater monetary value than he contributed. Name that Fallacy

Suppressed Evidence

Hasty Generalization (Converse Accident)

The fallacy occurs when there is a reasonable likelihood that the sample is not representative of the group. Such a likelihood may arise if the sample is either too small or not randomly selected. part to each part

argument against the person (ad hominem)

This fallacy always involves two arguers. One of them advances (either directly or implicitly) a certain argument, and the other then responds by directing his or her attention not to the first person's argument but to the first person himself. occurs in three forms: the ad hominem abusive, the ad hominem circumstantial, and the tu quoque.

Missing the Point (Ignoratio Elenchi)

This fallacy occurs when the premises of an argument support one particular conclusion, but then a different conclusion, often vaguely related to the correct conclusion, is drawn

Arguments that commit the fallacy of begging the question are normally valid.

True

Evaluate deductive arg: Since Moby Dick was written by Shakespeare, and Moby Dick is a science-fiction novel, it follows that Shakespeare wrote a science-fiction novel.

Valid, unsound; false premises, false conclusion

Appeal to Pity

When an arguer tries to get people to accept a conclusion by making them feel sorry for someone. Good arguments can evoke emotion, but also have good reasoning with them

Cognitive bias: Anchoring bias

When people are overreliant on the first piece of information they hear OR I know that you read last week that he cheated on his wife, but last year I read that they were happily married

Cognitive bias: Confirmation bias

When we listen to only to information that supports our perceptions My example: I think swimming is the hardest sport; my swim coach says that it is the most physically taxing because it uses every muscle. Like I thought, swimming is the most difficult sport

Define Fallacy

a defect in an argument that arises from either a mistake in reasoning or the creation of an illusion that makes a bad argument appear good. Deductive and Inductive arguments both have them

Formal Fallacy

a logical error that occurs in the form or structure of an argument; it is restricted to deductive arguments

Equivocation

a word or phrase is used, either explicitly or implicitly, in two different senses, also may spread the shift in meaning out over the course of a lengthy argument, arguer mispeaking

straw man fallacy

an arguer distorts an opponent's argument for the purpose of more easily attacking it, demolishes the distorted argument, and then concludes that the opponent's real argument has been demolished. always involves two arguers

deductive argument

an argument incorporating the claim that it is impossible for the conclusion to be false given that the premises are true. If the it is impossible for the conclusion to be false when the premises are true from some conclusion, then it valid. It is invalid if you can think of a counterexample. If it valid, and all true, then the argument is sound.

inductive argument

an argument incorporating the claim that it is improbable that the conclusion be false given that the premises are true. Strong when it is improbable that the conclusion is false with true premises. Weak when conclusion does not really follow from premises. Cogent when strong and all actually true premises. Uncogent otherwise

casual inference

an argument that proceeds from knowledge of a cause to a claim about an effect, or, conversely, from knowledge of an effect to a claim about a cause. specific instances can never be known with absolute certainty.

Appeal to the People (Ad Populum)

an attempt to persuade a person or group by appealing to the desire to be accepted or valued by others, or fear. causes mob mentality. direct approach addresses a large group of people. The indirect approach is used individually, and includes bandwagon, appeal to vanity, snobbery, to tradition,

Composition Fallacy

assuming that what is true for the individual is true for the whole, part to whole

Red Herring

committed when the arguer diverts the attention of the reader or listener by changing the subject to a different but sometimes subtly related one. ex=

division fallacy

committed when the conclusion of an argument depends on the erroneous transference of an attribute from a whole (or a class) onto its parts (or members)

begging the question

committed whenever the arguer creates the illusion that inadequate premises provide adequate support for the conclusion by leaving out a possibly false (shaky) key premise, by restating a possibly false premise as the conclusion, or by reasoning in a circle, "request for the source"

False Dichotomy

considers two unlikely alternatives as if they are the only ones available

Each element, such as hydrogen and iron, has a set of gaps—wavelengths that it absorbs rather than radiates. So if those wavelengths are missing from the spectrum, you know that that element is present in the star you are observing. What kind of argument?

deductive

Because triangle A is congruent with triangle B, and triangle A is isosceles, it follows that triangle B is isosceles. What kind of argument?

deductive argument, arg based on mathematics

No e-mail messages are eloquent creations. Some love letters are eloquent creations. Therefore, some love letters are not e-mail messages. What kind of argument?

deductive, categorical syllogism

Strength of Inductive Arguments

how probable it is that a conclusion follows a premise strong arguments: highly improbable that conclusion does not follow premises if they are true

The Wall Street Journal has an article on the new banking regulations. The Financial Times, like the Wall Street Journal, is a highly respected business publication. Therefore, the Financial Times probably also has an article on the new banking regulations.

inductive, argument from analogy

When I visited Dr. Ames about my cholesterol, she insisted that I go on a statin drug. She says everybody should be on a statin. And when I saw Dr. Collins for depression, he prescribed Prozac. And when the Prozac gave me nausea, he prescribed Zofran to stop the nausea. Doctors are all the same. They all take their orders from the pharmaceutical industry. Name that fallacy

key phrase: doctors are all the same. hasty generalization

The vast majority of car accidents occur within twenty miles of one's home. Apparently it is much more dangerous to drive close to home than far away from home. Name that Fallacy

missing the point or suppressed evidence

an Nonarguments

noninferential, simple explain a topic, may be a report, could be an opinion or expository statement, premises= not enough or don't claim to support conclusion

Appeal to Unqualified Authority

occurs when the cited authority or witness lacks credibility, person might lack the requisite expertise, might be biased or prejudiced, might have a motive to lie or disseminate "misinformation," or might lack the requisite ability to perceive or recall.

false cause fallacy

occurs whenever the link between premises and conclusion depends on some imagined causal connection that probably does not exist. One example is post hoc ergo propter hoc ("after this, therefore on account of this"). Another is non causa pro causa ("not the cause for the cause"). This variety is committed when what is taken to be the cause of something is not really the cause at all and the mistake is based on something other than mere temporal succession. Also, oversimplified cause and gambler's fallacy (independent events in a game of chance are falsely believed to be related)

Soundness of deductive arguments

premises and conclusion are all actually true and the argument is valid (so, if argument is invalid we know it is unsound)

Suppressed Evidence

quotes passages out of context, or ignores stronger evidence that supports a different conclusion

Cognitive bias: Placebo Effect

simply believing something to have a certain effect, causes it to have that effect my example: I knew treating myself to some ice cream would make me feel better, and it did!

Cogency of Inductive arguments

strength and truth of premises, for cogent arg must be strong and have all true premises

Evaluate inductive arg: The grave marker at Arlington National Cemetery says that John F. Kennedy is buried there. It must be the case that Kennedy really is buried in that cemetery.

strong and cogent

Evaluate inductive arg: People have been listening to rock and roll music for over a hundred years. Probably people will still be listening to it a year from now

strong, but uncogent. false premise, but if it were true conclusion would follow

weak analogy fallacy

the analogy is not strong enough to support the conclusion that is drawn.

Amphiboly

the arguer misinterprets an ambiguous statement and then draws a conclusion based on this faulty interpretation, original statement typically comes from someone other than the arguer, can arise from mistake in grammar and punctuation, listener misunderstanding

appeal to force fallacy

the assertion that you should do what I say or believe what I believe because, if you do not, I will harm you. Makes appeal to fear personal. Ex. Sesame street is the best show. I know you will agree because otherwise my brother will beat you up

Evaluate inductive arg: Franklin Delano Roosevelt said that we have nothing to fear but fear itself. Therefore, people have no reason to fear serial killers.

weak and uncogent, probably false conclusion

Accident (fallacy of relevance)

when a general rule is applied to a case it is not intended to cover,