Richard L Epstein

by Critical Thinking (3rd Edition) (pdf)

  ingredients."

  Dick: Lard is all natural, too.

  14. From an article in Smithsonian, vol. 32, no. 11, 2002, about irrigation of small farms in New Mexico:

  The practice of trading in water as a commodity, observes one activist, is like

  "selling sunshine."

  15. Maria: Suppose someone came up to you and offered you a sure-fire method for finding

  $100 bills on the street, for which he'd charge you only $5.95. You'd be crazy to buy it

  from him. After all, he could just as easily pick up the $100 bills himself. Besides, we

  know there aren't any $100 bills lying around the street, since any time there's a $100

  bill floating free you can be sure that someone will pick it up immediately. So why pay

  money to a stock analyst?

  16. Downloading computer software from someone you don't know is like accepting

  candy from a stranger.

  17. Flo's mother: It's just so hard raising Flo.

  Dick: How hard can it be to raise a kid? After all, I've trained two dogs.

  18. Tom: I can't believe you're out demonstrating against the U.S. fighting in Iraq.

  Dick: I'm against war—all wars. I'm a pacifist.

  Tom: So, if someone came up to you on the street and hit you from behind, you

  wouldn't turn and hit him back?

  19. We should take claims about extra-sensory perception seriously. Look, suppose no one

  in the world had a sense of smell except one person. He would walk along a country

  road where there is a high stone wall and tell his friend, "There are roses there." Or he

  would walk into a home and say, "Someone cooked onions here yesterday." These

  would seem extraordinary extra-sensory perceptions to his friends and acquaintances.

  Similarly, just because we don't understand and can't imagine a mechanism that would

  explain extra-sensory perception, we shouldn't stop the investigation.

  20. Tom: Seat belts cause accidents.

  Dick: Are you crazy? Seat belts save lives. Everyone knows that.

  Tom: No, they cause accidents. They may prevent serious injury in some accidents,

  but there are more accidents now because people use seat belts.

  Dick: Why's that?

  EXERCISES for Chapter 12 263

  Tom: The threat of getting killed or seriously injured in an accident is much less

  if you're wearing a seat belt. Because people reckon they are safer, they're less

  careful and drive faster. So they get into more accidents. Some guy at the

  University of Chicago looked at the numbers in the 1970s and found that there

  are fewer deaths per accident, but more accidents, so that the actual number of

  people getting killed remained about the same after seat belts were required.

  Dick: Well, if that's the case, we better not make any more improvements on cars.

  And we certainly shouldn't require motorcycle riders to wear helmets.

  21. Letter to the editor in the El Defensor Chieftain, Socorro, NM, March 29, 2003:

  This year's Legislative session and the bills against cockfighting have caused some

  heated arguments.

  The opposition's reasoning is ridiculous, considering that many of them do not

  understand anything about cockfighting. The people that are trying to ban our sport

  are not affected by it in any way, shape or form.

  A fellow cockfighter recently asked a lawyer, "How would you like it if we tried to

  take your license away?" Lawyers make their living practicing law; cockfighters make

  their living by buying, selling, raising and fighting roosters.

  Our occupations may differ, but the fact that we both pay our bills and support our

  families, makes us a lot alike. Leave us alone!

  We fight roosters and are proud of it. We are third-generation cockfighters and it

  has been in our family for over 50 years. Those of you who think no one actually makes

  a living this way are sadly mistaken—think again.

  In conclusion, we are a family and we are just trying to survive in this society.

  We teach our children to have morals and value their upbringing. Please don't take that

  away—it is all we have. Tara Parish

  22. I know I can't really feel a pain you have. But because we're so much alike in so many

  ways, I'm sure that you feel physical pain in roughly the same way I do.

  23. Dick: Our diet should be similar to that of cavemen—that's what our genes are

  programmed for.

  Zoe: You're nuts. Besides, it's cave dwellers, not "cavemen."

  24. God must exist. The way everything works together in nature, the adaptation of means

  to ends, the beauty, resembles, but far exceeds, what humans do. Everything works

  together as a fine piece of machinery, like a watch. So there must be some maker with

  intelligence behind all of nature. That is, God exists and is similar to human mind and

  intelligence.

  25. Voters in Arizona and California approved ballot measures Nov. 5 allowing prescrip-

  tions of marijuana and other controlled substances for certain patients.

  The most prevalent use is to ease the suffering of terminal patients or to counteract

  the side effects of chemotherapy. . . .

  The legal effect of the measures' passage is still up in the air, since the uses remain

  outlawed under federal statute. But retired General Barry McCaffrey, the White House's

  drug policy director, is quite certain about what the practical effect will be:

  264 CHAPTER 12 Reasoning by Analogy

  "Increased drug abuse in every category will be the inevitable result of the

  referenda," he said in a speech last week. "There could not be a worse message to young

  people than the provisions of these referenda. . . . They are being told that marijuana

  and other drugs are good, they are medicine."

  Apply this logic to the general's primary area of expertise:

  Does the necessity of maintaining a standing army and engaging in war to protect

  national interests send a message to teens to arm themselves and form street gangs? . . .

  There is a line between use and abuse of a necessary evil like lethal force or a powerful

  narcotic.

  Social, economic and political circumstances justify the use of lethal force in war;

  medical circumstances justify the use of drugs.

  But to think that teens or other forms of life lower on the food chain than generals are

  unable to differentiate between use and abuse may lead directly to the kind of logic under

  which students are expelled for possession of over-the-counter analgesics like Midol.

  Editorial, Albuquerque Journal, November, 1996

  a. What is the conclusion?

  b. What analogy does the editorial make?

  c. How does it use the methods for evaluating analogies?

  d. Are there any slanters or bad argument types?

  e. Is the argument good?

  26. a. Suppose that tomorrow good, highly reliable research is announced showing that oil

  derived from tails removed without anesthetic from healthy cats when applied to

  human skin reduces wrinkles significantly. Would it be justifiable to do further

  research and manufacture this oil?

  b. Same as (a) except that the oil is drunk with orange juice and significantly reduces

  the chance of lung cancer for smokers.

  c. Same as (a) except the oil is mixed with potatoes and eaten and significantly reduces

  the chance of heart disease and lengthens the lives of women.

  d. Same as (a) except that wh
en drunk, the oil kills off all viruses harmful to humans.

  27. Do Exercise 26 reading "dogs" for "cats."

  F u r t h e r Study Analogies are discussed in courses in criminal justice, ethics, and health sciences, among others. The exercise Tom did about how we justify treating dogs

  humanely is typical of the sort of problem and reasoning you'd encounter in a course

  on ethics. Some philosophy classes on reasoning or philosophy of science look at

  the nature of analogies more deeply. In the Science Workbook for this text you can

  read about how scientists reason with models as analogies, and Science Analyses 4.8,

  8, and 10.C deal with E S P .

  Writing Lesson 10

  You understand what reasoning by analogy is now. So write an argument using an

  analogy either for or against the following:

  Just as alcohol and tobacco are legal, we should legalize the use of

  marijuana.

  Check whether your instructor has chosen a different topic for this assignment.

  There are roughly three ways you can argue:

  • Marijuana is no worse than alcohol or tobacco, so we should legalize it.

  (Arguing from similarities.)

  • Marijuana is worse than alcohol and tobacco, so we should not legalize it.

  (Arguing from differences.)

  • Marijuana is no worse than alcohol or tobacco, but it is a mistake to

  have those legal, and we should not make the situation worse by

  legalizing marijuana.

  (Arguing from similarities.)

  Be sure to make explicit what prescriptive premises you are using.

  Write your argument as a maximum one page essay. It should be clear and

  well structured, since you will have written out the claims first for yourself. You

  shouldn't have to do major research for this, but at least be sure your premises are

  plausible.

  265

  13 Numbers?

  A. Misleading Claims with Numbers 268

  B. Graphs 270

  C. Averages 273

  Summary 274

  •Exercises for Chapter 13 275

  In this chapter we'll look at some ways you can get confused about numbers in

  claims. If your eyes are starting to glaze, if your mind is going blank with talk of

  numbers, relax. Numbers don't lie.

  267

  268 CHAPTER 13 Numbers?

  A. Misleading Claims with Numbers

  Zoe has 4 apples and Dick has 2 oranges. Who has more? More whatl

  When numbers are used it looks exact, but a vague or meaningless comparison

  gets no better by having a few numbers in it.

  There were twice as many rapes as murders in our town.

  Yes, that's a claim, but a misleading one. It seems to say something important, but

  what?

  It's getting really violent here. There were 12% more murders this year.

  This is also a mistaken comparison. If the town is growing rapidly and the

  number of tourists is growing even faster, it would be no surprise that the number of

  murders is going up, though the rate (how many murders per 100,000 population)

  might be going down. I'd feel safer in a town of one million that had 20 murders last

  year than in a small town of 25,000 that had 6. A numerical comparison where it

  doesn't make sense to compare the items is called comparing apples and oranges.

  Increases and decreases are comparisons, too:

  Attendance up 50% this week at performances of Othello!

  Tickets still available!

  Great ad, but what was the attendance last week? 25? 250? 1,000? We call it

  two times zero is still zero when someone gives a numerical comparison that makes something look impressive but the base of the comparison is not stated. For

  example, a clothing store advertises a sale of sweaters at "25% off." You take it to

  mean 25% off the price they used to charge which was $20, so you'd pay $15. But

  the store could mean 25% off the suggested retail price of $26, so now it's $19.50.

  Percentages can be misleading, too You see a stock for $60 and think it's a

  good deal. You buy it; a week later it's at $90, so you sell. You made $30—that's

  a 50% gain! Your buddy hears about it and buys the stock

  at $90; a week later it goes down to $60, so he panics

  and sells the stock. He lost $30—that's a 33.33% loss.

  The same $30 is a different percentage depending on where you started.

  And then there's the report that says unemployment is up 8%. That does not

  mean unemployment is at 8%. It means that if unemployment was 5%, it is now

  5.4%. There is a difference between "up" and "up to." Here's another example:

  X-Ray Cancer Risk Up to 3%

  The risk of cancer from common X-rays and increasingly popular CT scans

  ranges from less than 1 percent to about 3 percent, according to a new study. . . .

  The new research indicates the cancer risk—ranging from 0.6 percent to

  3.2 percent—varies depending on the frequency of X-rays and scans in 15

  countries surveyed. . . .

  SECTION A Misleading Claims with Numbers 269

  Of the 15 countries surveyed, the cancer risk believed linked to X-rays

  was lowest in Britain, where they are used least frequently. They estimated that

  0.6 percent of the cumulative British cancer risk for those 75 years old came

  from X-ray exposure, accounting for about 700 of the nation's annual cancer

  diagnoses. Beth Gardiner, Associated Press, January 30, 2004

  Sounds good, except when they say that the cancer risk is 1 percent, what do they

  mean? With percentages, you always need to ask: percentage of what!

  An article in the journal Science, vol. 292, uses percentages to assess risk in

  health care. Mammography screening, it says, can reduce the risk of breast cancer

  fatalities in women ages 50 to 74 by 25%. That seems like a real incentive for

  women of that age to get tested. But, the article points out, only 2 out of 1,000

  women without symptoms are actually likely to die of breast cancer within the next

  10 years. So reducing the risk by 25% just means that only 1 more woman in 1,000

  who undergoes screening in the next 10 years would be saved. Yet the other women

  who won't benefit from screening are subjected to X-rays, false positive tests, or

  treatment for slow-growing cancers that could be left alone. To make choices about

  health care you need not only the percentages, but the actual numbers, too.

  Still, it doesn't matter whether it's percentages or actual numbers if there's no

  way they could know the number. For example, on a National Public Radio news

  broadcast I heard:

  Breast feeding is up 16% from 1989.

  How could they know? Who was looking in all those homes? A survey? Who did

  they ask? Women chosen randomly? But lots of them don't have infants. Women

  who visited doctors? But lots of women, lots of poor ones, don't visit their doctors.

  What does "breast feeding" mean? Does a woman who breast feeds one day and

  then gives it up qualify as someone who breast feeds? Or one who breast feeds two

  weeks? Six months? Maybe NPR is reporting on a reliable survey (in the next

  chapter we'll look at what that means). But what they said is so vague and open to

  doubt as to how they could know it that we should ignore it as noise.

  Rich getting richer, except in Africa and Asia

  The rich got richer in most parts of the world last year, except for Asia and Africa.

 
There were nearly 7.2 million people around the globe in 2000 who had at

  least $1 million in investable assets, an increase of 180,000 from 1999, said a study

  released Monday. Their total wealth was estimated at $27 trillion, up 6 percent

  from $25.5 trillion the previous year.

  Albuquerque Tribune, May 15, 2001

  Where did they get these seemingly unknowable figures? What study? Who wants

  to let people know they're rich? This is a worthless report.

  270 CHAPTER 13 Numbers?

  B. Graphs

  Graphs can be useful in making comparisons clearer. But we have to be careful

  when reading them because they can conceal claims, mislead, or just be wrong.

  Example 1

  U.S. Private Universities U.S. Public Universities

  W. Baumol and A. S. Blinder, Economics: Principles and Policy

  Analysis You should check the information in a graph against your personal

  experience. The authors of this economics textbook say that the average hourly

  wage is about $13. So according to the graph the (average?) cost of a college

  education in 1997 at a U.S. public university was about $13/hour X 200 hours =

  $2,600. But that's unlikely to be enough for tuition and books for one year, much

  less housing and board—and certainly not for four years.

  Example 2 2001-2002

  2000-2001

  1999-2000

  1998-1999

  Socorro, N.M. Consolidated Schools Accountability Report, 2000-2001

  Analysis The numbers here are correct, but the graph greatly exaggerates the

  differences between years. The enrollment in 2001-2002 is 11.4% less than in

  1998-1999, but the difference in the lengths of the bars representing those

  enrollments is 66%. Visually the difference appears even greater because we're

  comparing areas instead of lengths. A graph is likely to distort comparisons if the

  baseline is not zero or if it uses bars.

  SECTION B Graphs 271

  Analysis Here we can see how the angle, the sharpness of increase and decrease,

  can be exaggerated greatly by the spacing of the scales on the axes. This affects our

  perception of the volatility and the amount of increase or decrease of prices.

  A graph can create misleading comparisons by the choice of how the measuring

  points on the axes are spaced.