High school students should see the exhibit. And just because it's a field trip does
not mean ALL students should attend. Parents who don't want their children to view
such an exhibit should have the option to say no. Likewise, those parents who do should
have the option to say yes.
Writing Lesson 11 335
B. No: Amid questions about HIV virus, trustees were right to reject trip
(Kris Jensen of Nevada Concerned Citizens)
Contrary to accusations, the School Board acted responsibly and wisely when it voted
not to allow the AIDS exhibit to be a school-sponsored field trip. The five board
members each had individual concerns which were all valid reasons as to why they
would not endorse the AIDS exhibit and send busloads of school children to the
museum.
Nevada Concerned Citizens had attended meetings and had fully reviewed the
materials (all 65 pages), when finally provided in the School Board back-up material.
Within the panels on display in the exhibit is a statement that we found to be untruthful
and were concerned about given the fact that they were seeking permission for Clark
County School District students to view this display on school time.
It reads: "HIV is spread only by sexual intercourse, contact with blood or from a
pregnant mother to her unborn child. By not sharing needles and not having sexual
intercourse without a condom, we can protect ourselves from infection with HIV."
This is a blatant lie. Risk may be reduced, but there is no 100 percent assurance that
we will be protected from infection by using a condom. What would happen when the
first student who read and believed that statement contracted AIDS?
After we read this statement, we raised the concern to the School Board that this is
inaccurate information and that we need to be totally honest with the students. There is
no room for error in contracting AIDS, it is 100 percent fatal. We must be completely
straight and say that the only safe way for protection from infection is abstinence. Other
methods may reduce risk, but don't tell people that they are protected and imply they are
safe.
Perhaps the fact that 230 million AIDS viruses can fit on the head of a pin and
certain condoms allow passage should tell us that there is no fail-safe way to protect
ourselves from infection with HIV other than abstinence.
Condoms leak. Perhaps the fact that dentists double and even triple glove when
dealing with AIDS patients, and their actions are nowhere near as risky, should send us a
message. So don't lead Clark County school kids down the primrose path with a false
assurance.
Former Secretary of Education William Bennet stated: ". . . 'safe sex' or even 'safer
sex' was no way to prevent AIDS, that people had to re-learn the value of traditional
morality or play a dangerous game."
Dr. Theresa Cranshaw, former member of the Presidential AIDS Commission, said:
"Saying that the use of condoms is 'safe sex' is in fact playing Russian roulette. A lot of
people will die in this dangerous game."
What about the three women out of 18 who contracted AIDS from their husbands
while using condoms during intercourse in Dr. Margaret Fischl's extensive study (that's
a 17 percent failure rate)!
Best yet, there's the report how an Australian man's sperm, frozen for months at
temperatures that would kill other viruses, infected four of the eight women
impregnated.
The point is that the jury is still out as to the "only" methods of transmission of
336 Writing Lesson 11
AIDS. Why would we put children at greater risk by telling them half-truths and giving
them false assurances?
We commend the five School Board members who had a concern with misinforma-
tion that could cost a student his/her life and voted not to lend their endorsement. We
encourage them to hold firm for the protection of Clark County school children.
Furthermore, we challenge the Lied Discovery Children's Museum and the National
Aids Exhibit Consortium to give their patrons honest and accurate information. Don't
ask the School Board to endorse false statements and contradictory information. Do not
risk lives by spreading inaccurate information that could have deadly results.
Cartoon Writing Lesson E
For each cartoon below there is a sentence that can be understood as a causal claim.
Argue either for or against that causal claim, based on what you see in the cartoon
and your general knowledge. Check that the necessary conditions for cause and
effect are satisfied and that you have not made any of the common mistakes in
reasoning about cause and effect. Compare Example 1 of Chapter 15, p. 310.
The falling apple knocked Dick unconscious.
The wasps chased Professor Zzzyzzx because he hit their nest.
338 Cartoon Writing Lesson E
4.
Suzy failed because she stayed up late dancing.
5.
Dick crashed because of the turtle.
6.
Dick had to hitchhike because he didn't get gas.
Review Chapters 12-15
In Chapters 1-5 we established the fundamentals of critical thinking. In Chapters
6-8 we looked at the structure of arguments. In Chapters 9-11 we considered ways
that people make bad arguments. In this section we looked at particular ways to
reason from experience.
Generally, when we reason from experience we cannot get certainty. Judging
arguments is more often weighing up the possibilities.
Analogies are common: We note similarities and draw conclusions. Often
that's all that's done, and then an analogy is more a suggestion for discussion than
an argument. To take an analogy seriously as an argument, the similarities have to
be spelled out clearly and a general principle drawing the conclusion from those
similarities is needed.
Analogies lead to generalizations. We generalize when we start with a claim
about some and conclude a claim about more. Generalizations often involve
numbers, and we looked at a few common problems when using numbers in
arguments. Then we saw that though we don't always know the details of how a
generalization was made, we can often judge whether the generalization is good by
reflecting on whether the sample is big enough, whether the sample is representative,
and whether the sample is studied well.
How big the sample needs to be and whether it is representative both depend on
the variation in the population. When there is a lot of variation, random sampling—
not to be confused with haphazard sampling—is the best way to get a representative
sample. With polls and surveys an estimate of the likelihood of the conclusion being
right and the margin of error should be given.
Analogies and generalizations play a role in perhaps the most important kind of
reasoning we do every day, figuring out cause and effect. We can set out necessary
conditions for there to be cause and effect. And we can survey some of the common
mistakes made when reasoning about cause and effect. The most pernicious is post
hoc ergo propter hoc reasoning (after this, therefore because of this). Often the best
we can say with our limited knowledge is that it's a coincidence.
When we reason abou
t cause and effect in populations with large variation, it's
hard, if not impossible, to specify the normal conditions. Typically a statistical causal
link is established. Considering the three main kinds of experiments used for those
arguments, we can see that, as with generalizations, a little common sense allows us
to make judgments about the truth of the conclusion.
339
340 REVIEW CHAPTERS 12-15
Review Exercises for Chapters 12-15
1. What is an argument?
2. What three tests must an argument pass to be good?
3. What is the difference between a valid argument and a strong argument?
4. Is every valid or strong argument with true premises good? Explain.
5. What is reasoning by analogy?
6. What are the steps in evaluating an analogy?
7. Define, for a collection of numbers:
a. The average.
b. The mean.
c. The median.
d. The mode.
8. What is a "two times zero is still zero" claim? Give an example.
9. a. What is a generalization?
b. What do we call the group being generalized from?
c. What do we call the group being generalized to?
10. What is a representative sample?
11. Is every randomly chosen sample representative? Explain.
12. Is it ever possible to make a good generalization from a sample of just one? Give an
explanation or example.
13. A poll says that the incumbent is preferred by 42% of the voters with a margin of error
of 3% and confidence level of 97%. What does that mean?
14. What three premises are needed for a good generalization?
15. What do we call a weak generalization from a sample that is obviously too small?
16. List the necessary conditions for there to be cause and effect.
17. Why is a perfect correlation not enough to establish cause and effect? Give an example.
18. List two common mistakes in reasoning about causes and give an example of each.
19. List the three common types of experiments used to establish cause in populations and
give an example of each.
20. Why is it better to reason well with someone even if you could convince him or her with
bad arguments?
21. a. What did you find most valuable in this course?
b. What did you find least valuable in this course?
c. Would you recommend this course to a friend? Why?
Evaluating Reasoning
Here is a summary of all the methods of evaluating reasoning we have studied.
Arguments
1. Read the entire passage and decide if there's an argument. If so, identify the
conclusion, then number every sentence or clause that might be a claim.
2. For each numbered part, decide:
a. Is it too vague or ambiguous to be a claim?
b. If it's vague, could we clear that up by looking at the rest of the argument?
Are the words implicitly defined?
c. If it's too vague, scratch it out as noise.
d. If it uses slanters, reword it neutrally.
3. Identify the claims that lead directly to the conclusion.
4. Identify any subarguments that are meant to support the claims that lead directly
to the conclusion.
5. See if the obvious objections have been considered.
a. List ones that occur to you as you read the passage.
b. See if they have been answered.
6. Note which claims in the argument are unsupported, and evaluate whether they
are plausible.
7. Evaluate each subargument as either valid or on the strong-weak scale.
a. Note if the subargument is a valid type or one of the fallacies we've seen.
b. If it is not valid or strong, can it be repaired?
c. If it can be repaired, do so and evaluate any added premises.
8. Evaluate the entire argument as either valid or on the strong-weak scale.
a. Note if the argument is a valid type or one of the fallacies we've seen.
b. If it is not valid or strong, can it be repaired?
c. If it can be repaired, do so and evaluate any added premises.
9. Decide whether the argument is good.
341
342 Evaluating Reasoning
Analogies
1. Is this an argument? What is the conclusion?
2. What is the comparison?
3. What are the premises (one or both sides of the comparison)?
4. What are the similarities?
5. Can we state the similarities as premises and find a general principle that covers
the two sides?
6. Does the general principle really apply to both sides?
Do the differences matter?
7. Evaluate the entire argument using the procedure for arguments.
Generalizing
1. Is this an argument? What is the conclusion?
2. Identify the sample and the population.
3. Are the three premises for a generalization plausible?
a. The sample is representative.
b. The sample is big enough.
c. The sample is studied well.
4. Evaluate the generalization using the procedure for arguments.
Cause and Effect
1. Identify what appears to be the causal claim.
If it is not too vague, describe each of the cause and effect with a claim.
2. Decide whether the purported cause and effect happened (the claims are true).
3. Decide whether the purported cause precedes the effect.
4. Evaluate whether it is (nearly) impossible for the claim describing the cause to be
true and the claim describing the effect to be false, relative to normal
conditions that you could provide.
5. Decide whether the cause makes a difference: If there were no cause, would the
effect still have happened?
6. Decide whether there is a common cause.
7. Make sure that none of the obvious mistakes are made:
b. It's not post hoc ergo propter hoc.
d. It's not tracing the cause too far back.
8. Decide whether you can conclude that there's a cause and effect relationship.
Evaluating Reasoning 343
Cause in Populations
1. Identify the kind of experiment that is used to support the conclusion:
controlled or uncontrolled; cause to effect, or effect to cause.
2. Decide whether you should accept the results of the experiment.
a. Was it conducted well?
(Use the methods for evaluating generalizations.)
b. Does it really support the conclusion?
(Use the steps for evaluating arguments and cause and effect.)
3. Decide whether the argument is good.
Composing
Good Arguments
By now you've learned a lot about how to compose an argument. Here is a summary
of some of the main points.
• If you don't have an argument, literary style won't salvage your essay.
• If the issue is vague, use definitions or rewrite the issue to make a
precise claim to deliberate.
• Don't make a clear issue vague by appealing to some common but
meaningless phrase, such as "This is a free country."
• Beware of questions used as claims. The reader might not answer
them the way you do.
• Your premises must be highly plausible, and there must be glue,
something that connects the premises to the conclusion. Your
argument must be impervious to the questions: So? Why?
• Don't claim more than you actually prove.
• There is often a trade-off: You can make your argument valid or
strong, but perhaps only at the expense of a rather dubious premise.
Or you can make all your premises clearly true, but leave out the
dubious premise that is needed to make the argument valid or strong.
Given the choice, opt for making the argument valid or strong. If it's
weak, no one should accept the conclusion. And if it's weak because
of an unstated premise, it is better to have that premise stated explicitly
so it can be the object of debate.
• Your reader should be able to follow how your argument is put
together. Indicator words are essential.
345
346 Composing Good Arguments
• Your argument won't get any better by weaseling with "I believe that"
or "I feel that." Your reader probably won't care about your feelings,
and they won't establish the truth of your conclusion.
• Your argument should be able to withstand the obvious counter-
arguments. It's wise to consider them in your essay.
• For some issues, the best argument may be one which concludes that
we should suspend judgment.
• Slanters turn off those you might want to convince— you 're preaching to
the converted. Fallacies just convince the careful reader that you're
dumb or intending to mislead.
• If you can't spell, if you can't write complete sentences, if you leave
words out, then you can't convince anyone. All the reader's effort
will be spent trying to decipher what you intended to say.
You should be able to distinguish a good argument from a bad one. Use the
critical abilities you have developed to read your own work. Learn to stand outside
your work and judge it, as you would an exercise in this text.
If you reason calmly and rationally you will earn the respect of others, and may
learn that others merit your respect, too.
Cartoon Writing Lesson F
For each of the following write the best argument you can that has as its conclusion
the claim that accompanies the cartoon. List only the premises and conclusion.
If you believe the best argument is only weak, explain why.
Manuel is angry.
Lee is allergic to bee stings.
Professor Zzzyzzx is trying to lose weight.