(Problems printing? Click here.)
"Causal" reasoning is reasoning about cause-and-effect relationships.
Causal arguments do not support claims about the existence or
non-existance of objects, nor about the occurance or non-occurance of
events. They just support claims about causal relationships. Thus no
causal argument would support a claim that tile roofs exist, nor would
any causal argument support a claim that baldness happens. But if
someone wanted to support a claim that tile roofs cause baldness, well,
then, that claim would have to be backed up by a causal argument.
(Notice that a causal claim is just a claim that A causes B. It is not a claim that anyone knows how A causes B.)
Causality is basically a relationship between one object or
event and another object or event. If we were to say that A causes B, we
would mean that there is a relationship between A and B such that
whenever A occurs, we should expect B to occur also. Causal claims are
therefore conditional predictions. They are predictions about what will
happen next IF something else has just happened. Causal arguments are
therefore attempts to get people to believe in these predictions. Causal
arguments cannot prove that anything other than a relationship exists. No causal argument can prove that A exists or that B exists.
For this reason, causal arguments can only establish relationships
between known entities. If we don't already know that A exists and that B
exists, we cannot make a causal argument about A and B. (We will cover
arguments that prove things exist in the next chapter.)
Causal claims can only be justified on the basis of established
correlations. It is often said that "correlation does not prove
causation." This is completely and utterly false. Correlation is the
only thing that ever proves causation. It's true that not every
correlation proves causation, but every causal relationship that has
ever been proved, has been proved on the basis of a correlation. (Thus
the claim that "correlation does not prove causation" is logically
analogous to the claim that "evidence does not prove guilt" in a court
of law.) The trick here is to figure out which correlations prove
causation, and which don't.
Causal relationships are usually not one-to-one relationships. Causes
can have multiple effects, and effects can have multiple causes.
Cigarette smoking does not cause cancer, emphysema or heart attack in everyone
who smokes cigarettes. But we can bet that a group of a thousand people
who smoke heavily we will see more cases of cancer, emphysema and heart
attack than in a demographically identical group of a thousand
nonsmokers. And ciggies are not the only things that cause cancer,
emphysema and heart attack. So a cause is something that makes the
effect more likely to happen but usually does not guarantee that the effect will happen.
It is important to remember that causal arguments do not have to come with explanations. When smoking was established as a cause of cancer, nobody had any idea how
smoking managed to cause cancer. Nevertheless, the strong correlation
between smoking cigarettes and getting cancer convinced reasonable
people that a causal link existed. It didn't matter that nobody had any
idea how smoking did it, all that mattered was that the correlation
between cigarettes and cancer was so strong that no other explanation
made sense. All that is necessary to establish a causal link is that a strong correlation be established. Explanations are immaterial to this correlation, so the lack of an explanation is never a weakness in a causal argument.
The way to evaluate a causal argument is to ask whether the known
correlation is strong enough to justify the causal claim and, if it is,
to then ask if all other causal possibilities have been eliminated. If it is, and they have, then your argument is good. If it isn't, or
they haven't, then the argument sucks. While an argument that tile
roofs cause baldness would have to start with some correlation
between tile roofs and baldness, it wouldn't get very far
unless it included reasons to eliminate all other possible causes
of baldness, like, for instance, salsa music. (We wouldn't have to
eliminate UFOs however. The fact that something has never been proved to
exist is generally enough to remove it from consideration when we're
If somebody were to say that we should abolish tile roofs because they
cause baldness we would evaluate his "causal claim" by asking him to
give evidence of a correlation between baldness and tile roofs. If it
turned out that men started losing their hair the moment they went under
a tile roof, and that men who never lived under tile roofs never went
bald, then we would have a strong correlation, and good reason to think
that tile roofs cause baldness. If it turned out that men went bald or
not independently of whether or not they lived under a tile roof, then
we would have no correlation, and no reason to think that tile roofs
cause baldness. So a causal argument that comes without at least some
evidence of a correlation is always a bad argument.
First, some terminology. A positive correlation is when two
things tend to happen together. Tile roofs and baldness are positively
correlated if it is the case that tile roofs tend to show up every time
baldness occurs, and vice versa. It's when two things tend to be absent
at the same time. Tile roofs and baldness are positively correlated if
it is the case that tile roofs tend to be absent every time baldness is
also absent, and vice versa. (I'm not sure those "vice versas"
A negative correlation is where occurances of one thing are correlated with non-occurrences of another thing.
John Stuart Mill figured out five different ways to support a causal
connection, depending on what kind of evidence you have. (These methods
may turn out to be "just common sense." I've noticed that students
often have a hard time understanding explanations of Mill's methods.
However, when I give those students exercises designed to test their
ability to apply Mill's methods, they find those exercises ludicrously
easy. This suggests that what I grandly describe as "Mill's Methods"
can be figured out by community college students with no previous
training in those methods. So, if you don't understand these
explanations, don't worry about it. You will probably be able to do the
Mill's method of agreement relies on positive correlations. It
basically says rule out everything that is not necessary to bring about
the effect, and what is left over is more likely to be the cause. Say we
have a population of one thousand bald men and the only thing all of
them have in common is that each of them spends long periods of time
under a tile roof. If this were true, then anything else that was
offered as a candidate for the cause could be eliminated by pointing out
that somebody got bald without being exposed to that thing. Since tile
roof is the only thing that cannot be so eliminated, we have good reason
to think that tile roof is the cause.
Mill's method of difference says rule out everything that is not
sufficient to bring about the effect. Say we have a population of one
thousand hairy men and one bald man who lives apart from them under a
tile roof. The only thing the hairy men all have in common is that none
of them lives under a tile roof. In this case any other causal candidate
could be eliminated by pointing out that somebody was exposed to that
thing without getting bald. Since tile roof is the only thing that
cannot be ruled out that way, we have good reason to think the tile roof
is the cause of the baldness.
Mill's "joint method" just means applying both methods together
to the same data set. If two things are both positively and negatively
correlated, then that could be strong evidence that one of them
causes the other.
Mill method of concomitant variation says look for something
that varies in proportion to the effect. Say that Al has lived under
tile for 7 years and is 10% bald, Ben has lived under tile for 14 years
and is 20% bald, Cal lived under tile for 21 years and is 30% bald, Don
has lived under tile 28 years for 40% baldness, Ed has 35 years and 50%,
Finn 42 years and 60%, Greg 49 years and 70%, Hal 56 years and 80%, Ian
63 years and 90% while Jack has spent seventy years living under a tile
roof and is completely bald. Since the amount of baldness goes up and
down with the time of residence under tile, and if nothing else
correlates in this way, this would give us good reason to think that
living under a tile roof causes baldness. Remember that the
corespondance doesn't have to be one to one. It can be any ratio at all,
just as long as that ratio is constant across instances.
Mill's method of residuals is a way of figuring out how much of
some effect can be attributed to some particular cause. Say that we know
that polka music causes baldness in 4 percent of listeners, plaid
shirts cause baldness in 8 percent of wearers, and that jumping jacks
cause baldness in 16 percent of jumpers. And say that we know that these
are the only causes of baldness apart from tile roofs. Finally say that
we know that yesterday one million men wore plaid shirts to do jumping
jacks to polka music under a tile roof, and 40 percent of them became
bald. Ignoring the tile, we can account for no more than 32 percent of
these baldnesses, (4+8+16=28), so being under a tile roof must cause
baldness in at least 12 percent (40-28=12) of men.
Now apply Mill's methods to the following problems, and then evaluate
the arguments that follow the problems. See if you think the person
making a causal argument in each dialog is correctly applying Mill's
Several patients at Chicago Soap Hospital are experiencing bizarre drug
side effects. The hospital administrator, Dr. Whatmeworry, is going
crazy, and has hired several people to figure out what is going on.
Unfortunately, none of them seem to know what they're doing. Your job is
to sort through the arguments and figure out who, if anyone, knows what
he's talking about.
Some patients in Ward 1 are turning into fairies and have turned several doctors into animals. The patients who are growing gossamer wings and buying pixie hats are on Unicorp, Verlag, Xindeco and Zydigm. Those who are merely looking on in horror are on Verlag, Zydigm and Unicorp.
The patients in Ward 2 have all acquired the ability
to shoot low energy laser beams from their eyeballs, which they use to
irritate their nurses, warm beverages and vaporize insects. Patient Abel is on Terraplex, Omniken, Shegos and Permax. Patient Baker is on Omniken, Shegos and Terraplex. Patient Cooper is on Terraplex, Shegos and Permax. Patient Dasia is on Shegos, Omniken and Permax.
Ward 3 Patients are channeling famous generals of the
past. They are now in great demand by TV networks as commentators on
various wars. The camera crews are disrupting hospital operations, and
one patient is faking symptoms (pretending to channel Buffy the Vampire
Slayer) in order to get on The McLaughlin Group. Patient Killian is channeling Caesar and Napoleon. She is on Invap 40mg, Kolvox 100mg, Minafax 300mg, and Nasdaq 1mg. Patient Lomax is channeling Rommel, Wellington, Alexander and Sun-Tzu and she is on Invap 10mg, Kolvox 200mg, Minafax 600mg and Nasdaq 2mg. Patient Miles is just channeling Vinegar Joe Stilwell and she is on Invap 30mg, Kolvox 50mg, Minafax 900mg and Nasdaq 1mg. Finally, Patient North is channeling Grant, Zhukov and Sharon. She is on Invap 20mg, Kolvox 150mg, Minafax 600mg and Nasdaq 4mg.
Some patients in Ward 4 are growing extra limbs, which
are presenting interesting possibilities for getting around the ward
and possible future sporting events. Patient Eggar is growing an extra left foot from his right elbow, and is on Quindor, Dynastar, Comdex and Gennum. Patient Harris has no extra limbs, and is on Dynastar, Fitel and Gennum. Patient Frank amuses children with the extra arm growing out of his left kneecap, and is on Comdex, Dynastar, Fitel, Quindor, and Gennum. Patient Irvin is perfectly normal and on Fitel, Gennum and Comdex. Patient Gregg
makes interesting gestures with the extra hand that has grown out of
where his nose used to be. He is on Quindor, Comdex, Fitel and Dynastar.
Patient Jakes has two arms growing from his tailbone, and can give himself a back massage. He is on Fitel, Gennum and Comdex.
Here are the arguments I want you to evaluate.
Exercise 1 Daryl. Don't take Zydigm! All of the people who turned into fairies took Zydigm, so it must be the cause!
Gwendolyn. Not everybody who took Zydigm turned into a fairy, so it's probably not the cause.
Exercise 2 Aliya.
The drug that gives people the ability to shoot laser beams from their
eyes must be Terraplex. Able, Baker and Cooper all took Terraplex, and
they all got laser vision.
Karson. Yeah, but Dasia got laser eyes too, and she didn't take Terraplex.
Exercise 3 Gianni.
The drug that lets you channel famous generals must be Nasdaq. Miles
took 1 milligram of Nasdaq and channeled just one general, that's a
1-to-1 correlation, so Nasdaq must be the drug.
Susana. But Killian also took 1 milligram of Nasdaq, and she
channeled 2 generals. Lomax took two milligrams, but she channeled four
generals! Neither of those is a 1-to-1 correlation, so Nasdaq probably
isn't the drug. And anyway, it doesn't have to be one unit of the drug
to one general. We have to look for a situation where the number of
generals goes up and down in exactly the same way that the dosage of the
drug goes up and down.
Exercise 4. Zoie. Dynastar must be the drug that is causing the extra limbs. Eggar, Frank and Gregg all took Dynastar and all grew extra limbs.
Tristian. But Harris also took Dynastar and didn't grow any extra limbs, and Jakes grew extra limbs without taking Dynastar.
Arguing Against A Causal Claim
There are two basic ways to argue against a causal claim. I call these
the "inconvenient fact method" and the "not so fast" method.
The inconvenient fact method is pretty simple. You'll
notice in the dialogues above the person arguing against the first
person's causal claim does so by bringing up some fact that cannot
easily be explained on the assumption that the first person's causal
claim is true. In the above dialogues, the second speaker gives us some
reason to think that the first speaker has not applied Mill's methods
correctly. The best causal argument will be the one that best fits the
observed facts. If you can show that some causal claim does not fit the
observed facts, you will have shown that the argument supporting that
claim is not a good argument. The most inconvenient fact of all would of
course be the fact that something else was just as strongly correlated
with effect as the purported cause. If we have just as good evidence
that something else causes the effect, then the evidence we have doesn't prove that our purported "cause" is the cause.
The not so fast method is applied to causal arguments
that survive the inconvenient fact method. Such an argument presents us
with an apparently good correlation. The not so fast method works by
presenting an alternative explanation for that correlation. If that
alternative explanation is at least roughly as good an explanation as
the original causal claim, then the argument supporting that causal
claim is no good. Consider the following.
Okay, I understand that some people who took Zydigm didn't turn into
fairies, but, it is a fact that all of the people who turned into
fairies did take Zydigm. Nobody who didn't take Zydigm turned into a
fairy, and Zydigm could be one of those causes that doesn't work every
time. So I think that Zydigm probably is the drug that is causing people
to turn into fairies.
Amya. Not so fast Jack! I mean Nasir. The same thing
is true of Unicorp and Verlag. All of the people who turned into fairies
took Unicorp and all of the people who turned into fairies took also
Verlag. So the evidence is just as good for Unicorp and Verlag being the
cause as it is for Zydigm being the cause of the fairification.
If Amya is right that Unicorp and Verlag are just as likely as Zydigm
to be the cause, then Nasir's argument in favor of Zydigm is no good.
Evaluating Causal Arguments
To evaluate a causal argument you must figure out two things. First,
you must figure out whether the causal claim offered is a good
explanation for the observed correlation. Second, you must figure out
whether or not there is any other reasonable explanation for that
correlation. If it turns out that the offered causal claim really isn't a
good explanation for all of the observed facts, then the argument is no
good. If it turns out that some other explanation for the observed
facts is just as good an explanation as the causal claim, then the
argument is no good.
Since basically any bad causal argument can be called a "false cause"
fallacy, I'm going to continue my discussion of bad causal arguments
under that heading.
The classic False Cause fallacy assumes a causal connection based on a
trivial correlation. Anyone who makes a causal claim based on anecdotal evidence commits the fallacy of false cause.
Interviewer. "Coach, can you tell me why the fans are tossing cans of beans on to the field?
Coach. "Well, we haven't done well this season. We only beat
Milwaukee, Dallas and Fargo. Just before that Milwaukee game I was
embarrassed by a noisy attack of flatulence. Then, as I was psyching the
team up for the Dallas game..."
Interviewer. "That was you? I thought it was a low-flying jet!"
Coach. "No that was me..."
Interviewer. "And the cheerleaders who fainted before the Fargo game?"
Coach. "Me again, I'm afraid."
Interviewer. "And so the beans..."
Coach. "If you'll excuse me, I think I can choke down another can.
I love your sister, but every time she comes to California we have an
earthquake. So we can't invite her again until I've finished
earthquake-proofing my collection of decorative plates.
Just because something is the only cause you can think of doesn't mean it has any causal relationship to the effect.
Pete: Since 1985,
the average SAT scores of the incoming freshmen at Miskatonic University
have consistently been about 10% better than they were before 1985.
Nothing important changed in or around 1985. In fact, we've checked all
the things that the schools could be doing that could possibly cause a
rise in SAT scores, and we found that none of them changed
significantly, so it isn't due to anything that local educators are
Ona: Have you forgotten that I‘ve been teaching at Miskatonic since 1985. Obviously, that's the reason.
Pete: How do you figure that?
Ona: Well, duh, before I got here, the scores were bad. After I got here, the scores got better.
Sometimes people commit false cause when they get confused about causal
relationships. People often assume that one thing causes (or must
cause) another thing merely because the two things are strongly
associated in their minds. But a mental association is a far cry from a
Ignoring Possible Alternative Cause.
One way to look at causal arguments is to see them as claiming that the
only way to explain the frequency of a certain event is to assume that
it is caused by some particular other kind of event. This means that
whenever there's something else that's equally well correlated with the
effect, it follows that that something else could just as easily have
been what caused the effect, and so the argument fails to prove the
causal conclusion it was intended to prove.
Causal reasoning requires careful attention to detail, and a
willingness to follow the evidence wherever it actually leads. Consider
the following problem.
Exercise 5 The village of
Ferlinghetti has been famous for its locally produced mineral water for
about 150 years. However, the village also has a problem with adult
asthma. Many of the town's adults spend much of their time coughing and
wheezing. Locals believe that the mineral water reduces or prevents the
asthma and have been drinking more and more of it since the asthma
problem was first identified in 1852. The asthma problem has grown
slowly but steadily worse, with no interruptions, since the early 1850s.
Asthma attacks do not get any worse or any better at any particular
time of day or time of year. The leading citizens in the town have
identified four possible causes of the asthma. A tin mine in the
mountains produces runoff, which runs into the local river, from which
the town draws all its drinking water. (Fortunately, the mineral water
comes from a deep mountain spring that is not at all affected by the
runoff.) A perfume factory in the next valley produces fumes, which
drift over to Ferlinghetti. Farmers in the nearby plain use a special
kind of wheat, which releases pollen that is carried into Ferlinghetti
by the prevailing winds. Bats from the local woods fly into the town at
night to feed on insects, and leave fur and skin flakes that hang in the
air for about an hour after they fly through. The tin mine has been in
continuous operation at the same level of production since Roman times.
The perfume factory was built in 1843, but was completely shut down for
both world war one and world war two. The special wheat was introduced
in 1840. The local species of bat was discovered and classified in 1845
when local kids found caves containing both the bats and accumulations
of bat droppings that proved to be dozens of feet thick. You are a
scientist called in to investigate the situation and discover the cause
of the asthma problem.
The town mayor
argues, "it's the tin mine in the mountains, because that runoff water
does get into the local drinking water. It must have started running off
in 1852 and the amount of water running off must have gotten larger and
larger since then."
The chief of police claims that "the perfume factory
has to be the cause. There must be something in the perfume fumes that
causes asthma, and they must have been using it continuously since
The town drunk confides in you that "the wheat must be
the cause. They've been growing it continuously since at least 1852, so
it's perfectly well correlated."
And the town librarian says "it's the bats! Aaaaaaaaaaagh! They're after me! Keep them away, keep them away! Send for Buffy now!"
Apply careful causal reasoning to the problem. You will find the answe very clear once you write down and organize all the facts given above. (You can print out just this problem if you download ferlinghetti.htm or ferlinghetti.rtf.)
Ignoring a Possible Common Cause
Remember that a strong correlation, by itself, does not prove
causality. The right way to show causality is to demonstrate a strong
correlation that cannot be exaplained any other way. When there is
another reasonable explanation for the putative causal relationship, the
argument commits the fallacy of "ignoring a possible common cause."
Remember, it is sometimes the case that two things are correlated, not
because one causes the other, but because some third factor causes
Every time I put on a little weight, I lose a little hair. So if I exercise and go on a diet, I'll stop losing my hair.
Ignoring a common cause might be easier to understand if it was called "ignoring a possible common cause" because it is the fact that some third thing might
be causing the correlation that makes the argument fail. Strictly
speaking, all you have to to refute any causal argument and it is a very
popular fallacy. It is often commited by people
who want to believe that drug use, by itself, causes crime.
If there is any reasonable possibility that a person's criminality and
drug use have a common cause, such as poor upbringing or exposure to
scofflaw culture, such as could reasonably be thought to have caused
criminalty without exposure to drugs, then the correlation between drug
use and criminality cannot prove that the drug use caused the criminal
Even when there is a strong correlation that cannot be reasonably
explained without assuming a causal realtionship between the two events,
people may be confused about which is the cause and which is the
effect. People can commit false cause by completely reversing a causal
relationship. That is to say, two things are correlated, but the wrong
thing is identified as the cause.
Reversing Cause and Effect
Have you noticed how Jane gets
depressed every time her cancer gets worse. If we could just cheer her
up, that would take care of that nasty cancer!
Here the arguer has reversed cause and effect. by
mistaking the effect for the cause and the cause for the effect. The two
things are undoubtedly correlated, and there is no third element that
could cause both things, but the wrong event is identified as the cause.
Reversing the Direction of the Effect
Finally, a more subtle, and perhaps more
common fallacy is when an arguer correctly identifies a cause, but
reverses the direction of the effect. The arguer mighy, say, have
noticed that the masses of water shot out of fire-hoses are associated
with building fires, but erroneously assumes that adding the water to
the building causes the fire, or that adding water makes the fire burn more fiercely. Because I can't think of a better name for it, I call this reversing the direction of the effect.
Why do we have drug laws? We have to
have them because of all those drug-related murders! Those dealers will
kill to keep their activities secret, you know!
Notice that the arguer here believes that laws against possession, use and sale of drugs reduce
the murder rate. Also notice that the arguer does not offer any data
whatsoever. Finally, notice that the arguer ignores a well-known causal
relationship between criminalization of activities and murder. Students
of history will recall that the criminalization of alcohol trafficking
in the United States was followed by an enormous increase in the number
of murders related to alcohol trafficking. This murder rate was
drastically reduced by the later legalization of alcohol trafficking.
Generally speaking, people do not kill to conceal activities that are
But the government of Slobovia had to
imprision those peaceful protestors! Don't you know that disagreement with the government can escalate to violent opposition?
Here the arguer correctly connects political repression with changes in
the level of political violence. But he illegitimately assumes that
political repression reduces or prevents political
violence. The right way to prove such a thing would be to give evidence
that repressive countries tend to have lower levels of political
violence than non-repressive countries, which he has not done.
Begging the Question
I want to emphasize very strongly that a mental association is no substitute for actual evidence. Just because two things are associated in your mind, or you think that one thing must
cause another, you cannot even begin to have an argument to that effect
until you come up with some real facts. To argue that one thing must
cause another merely because you think that it must be so is simply to beg the question. Consider the following.
Of course welfare causes dependency! It just stands to reason that
people on welfare will want to stay on welfare for as long as possible.
Are you crazy? I think it stands to reason that people on welfare will
want to get off welfare as soon as possible. We can't both be right, so I
don't think talking about "stands to reason" tells us anything about
Notice that Rylan offers his own opinion as evidence. Unsupported by evidence, his claim that his opinion "stands to reason" is nonsense. Things only
stand to reason when they are supported by a good argument. Offering
one's personal opinion as evidence is not an argument. Aspen, however,
has a good argument. Notice that her conclusion is just that
arguments like Rylan's can't prove anything. True, her opinion that
people on welfare will want to get off welfare as soon as possible is
just her opinion, but it is a fact that she holds that opinion, which
shows that Rylan's opinion isn't the only one out there, which
is enough to show that Rylan's argument is no good. (Generally, people
who tell you that something "stands to reason" instead of giving you an
argument are simply trying to cover the fact that they have no
People can of course commit fallacies when attacking a causal argument. The most common fallacy in this area is red herring.
The "inconvenient fact" method of attacking causal arguments doesn't
always work. Sometimes the fact in question isn't even remotely
inconvenient for the argument. When this happens, the person attacking
the argument has committed a red herring fallacy.
Suppose that the "Hacking Cough" study is a long-term study comparing a
group of heavy cigarette smokers to a group of nonsmokers has found
that, over time, cases of lung cancer crop up in the smoking group at a
rate five times that which they crop up in the non-smoking group. Some
people take the Hacking Cough Study to have proved that cigarette
smoking causes lung cancer. Other people claim that it doesn't prove
that cigarette smoking causes lung cancer. If we pretend that these
people give the following arguments, we would be pretending that they
all commit red herring fallacies, because all the following arguments
are red herrings.
The Hacking Cough Study doesn't prove that smoking causes lung cancer because it is a fact that some people who smoke heavily never get lung cancer.
You cannot claim that the Hacking Cough Study proves that smoking
causes lung cancer because no one, including the authors of the study,
can explain just how it is that smoking manages to cause lung cancer.
Plenty of nonsmokers get lung cancer, so it can't be true that cigarette smoking causes lung cancer.
The first argument is a fallacy because the statement "A causes B" only
means "A raises the probability that B will happen," not "A always makes B happen." The second one is a fallacy because causal arguments don't have to provide explanations. Strong evidence of a strong correlation always
establishes a cause and effect relationship, whether or not we can
explain that relationship. And finally, the third argument is also a red
herring because the study doesn't have to prove that smoking is the only cause of lung cancer in order to prove that it is a cause of lung cancer.
Consistency With Available Evidence
Sometimes people will insist that some causal claim is true even though
all the evidence they have implies that it is false. The following is a
paraphrase of an actual conversation. (Only the names have been
It's obvious that welfare causes dependency, because someone who's
getting money without working is going to want to keep on taking it
Issac. You know, I don't think
it's fair of you to project your own preferences on other people. What
makes you think that people on welfare feel the same way you would in
Beau. What are you talking about? I wouldn't feel that way! I'd want to get off welfare as soon as possible.
Issac. Oh, sorry. I guess you
were basing this on people you know. Still, you shouldn't assume that
the people who end up on welfare are like the people in your family, and
your other friends and acquaintances.
Beau. Hey! None of my family are like that! None of my friends would want to stay on welfare. In fact, I don't know anyone who would.
Issac. So you're saying that someone who's getting money without working is going to want to keep on taking it easy, even though all of the actual human beings you know about wouldn't want to keep on taking it easy, even if they were getting money without working.
Beau. Now you've got it.
The first point is, of course, that Beau's conclusion is contradicted by all the evidence he has. He's saying that all people are suceptible
to being made dependent by welfare even though all of the people he knows lack
that suceptibility. The second point to notice is that Beau is not even
using the right kind of strategy to establish a causal claim. His first
statement is actually a question begging fallacy,
since the statement "someone who's getting money without working is
going to want to keep on taking it easy" is simply a more general
statement of the claim "welfare causes dependency." The two claims are
not different enough to make the premise acceptable to anyone who
rejected the conclusion. Issac treats Beau's argument as a
generalization as a way of getting Beau to admit that he has evidence
that contradicts his conclusion. Beau may indeed be generalizing, since he might
have an idea in his head of what he thinks a typical welfare recipiant
is like, and is generalizing from this imaginary person to real welfare
recipients. Of course, imaginary evidence never counts.
(Therefore arguments based on imaginary evidence always commit the
relevance fallacy of red herring.)
Causal Chains and Slippery Slopes
The fallacy of slippery slope combines a whole string of dubious causal claims. The difference between a slippery slope fallacy and a legitimate causal chain
argument is that the legitimate argument depends upon a series of
well-established causal relationships while the slippery slope includes
at least one dubious or speculative causal claim.
Censoring hardcore pornography will
soon lead to censorship of softcore pornography, which in turn will lead
to suppression of harmless erotica like swimsuit photos, and that
itself will finally cause censorship of nude pictures in medical
If you make marijuana legal then it'll be magic mushrooms. If 'shrooms,
then speed, and after that, peyote! Then cocaine won't be far behind.
Which means crack! And what about heroin? And acid! Then there's angel
dust, and finally those designer drugs that make people's heads explode!
So if we make marijuana legal, decent people won't be able to sleep for
the sound of all the exploding heads.
Would legalizing marijuana cause 'shrooms to become legal? Would legalizing 'shrooms cause speed to become legal? Would legalizing speed cause peyote to become legal? Would legalizing peyote cause crack to become legal? Would legalizing crack cause heroin to become legal? Would legalizing heroin cause angel dust to become legal? Would legalizing angel dust cause designer drugs to become legal? Is there anything about legalizing one drug that makes it impossible, or extremely difficult to avoid legalizing the next drug in the sequence? If there's any point where we can legalize one (relatively harmless) drug without having to legalize the next (more harmful) drug, the causal chain snaps, and the slippery-slope argument fails.
(Slippery-slope is what logicians call a presumption
fallacy, because the arguer illegitimately assumes that, because the
first element in a chain seems to him to be associated with the second
element in the chain, it will then follow that allowing the first
element to exist will cause the second element to come to pass.
But if a causal relationship has not been proved to exist between these
two elements, then he simply cannot assume that one will cause the
Another important issue in causal reasoning is the reasonableness
of a causal prediction. A causal prediction is a claim that some action
that we contemplate taking will have some particular effect. For
instance, the claim that invading Iraq will make us more secure is a
causal prediction because it holds that if we invade Iraq (as we just
did), the foreseeable future will be more secure for us than if we had
not invaded Iraq. An opposing causal prediction might be that the
invasion will make us less secure. Such predictions can be partially
tested by waiting until after the fact and seeing if the claimed effect
actually comes to pass. In the case of the Iraqi invasion, for instance,
the first prediction would lead one to expect decreased security at
airports, fewer terrorist alerts and less money spent on homeland
security, whereas the second prediction would lead one to expect at
least a continuing high level of security, more terrorist alerts and
more money spent on homeland security. But there are two problems. The
first is that there may be other factors involved, so that the real
effects are hidden. For instance, it may in fact be true that the
invasion increases our security, but some other independent factor,
(say, the final fruition of a terrorist plot that was begun well before
the invasion was announced, or the loss of competent security
administrators in a car accident) decreases our security, hiding the
gain from the invasion. The second problem is that we need to be able to
predict the effects of our actions before we act. We cannot undo an
invasion, so we have to be sure of its effects before we go
ahead and do it. For this reason, a great deal of causal reasoning is
done without the benefit of definitive evidence regarding the particular
kind of action contemplated. The best we can do sometimes is to think
about what we might reasonably expect to happen based on generally known
causal rules, and such thinking, like any thinking, always runs the
risk of committing non-causal as well as causal fallacies. So look out
for any and all of the fallacies we've learned previously as well as the
If you're not already sick of hearing about the subject, here's a little story about causal reasoning: causalstory.htm
For each of the following argument pairs, I want you to do following two things:
1. Work out which argument is weaker by applying the correct rules of analysis.
2. Write your own, original critique of the weaker argument.
Remember that the right way to establish a causal relationship is to show that:
1. The thing that's supposed to be the cause is very strongly correlated with the effect.
2. Whenever the two things happen together, the thing that's supposed to be the cause happens before the effect.
3. The correlation cannot reasonably be explained any other way.
Remember that the very best critiques will include both the correct fallacy name and the crucial fact(s), explained in such a way that a reasonable reader will be able to immediately see why the weak argument is bad.
Once you have made your best effort to analyze all the arguments and
write your own critiques, check your answers at the end of the chapter
Exercise 6. Raegan. How can you stand there and protest the war? Don't you know our boys are over there?
Rohan. Well, if there wasn't a war, wouldn't they be back here instead of over there?
Exercise 7. Glenn. Studies show that people who
dance are five times as likely to have knobby knees as people who don't
dance, so dancing causes knobby knees.
Savanah. Hah! That's ridiculous! Don't you know
that everyone of those studies recorded a bunch of people who danced
around for years and never got knobby knees, so it must be blindingly
obvious that dancing doesn't cause knobby knees.
Exercise 8. Tobias. We must ban digital cameras
immediately! A major 17-country study has shown that people who use
digital cameras are 10 times more likely than non-digicam-users to
become lawyers, and that the increase in lawyerism in any area is
perfectly correlated with the local increase in digicam use. The study
has been checked over by 217 experts who all independently certified it
as perfectly conducted and demographically appropriate, with absolutely
no reason to think that the study might be flawed in any respect. So we
must ban digicams before we are buried in lawyers.
Leila. I've seen that study. I've read that study
from cover to cover. And I can tell you we don't need to worry. This
study fails to prove that digicam use causes lawyerism because it
totally fails to explain how digicam use causes lawyerism.
Exercise 9. Everett. I've just discovered some
disturbing news about Histafix, the medicine to relieve allergy
symptoms. Did you know that once allergy sufferers start taking it, they
almost never stop! Obviously, this means that taking Histafix causes
dependence on Histafix. I just heard that thousands of people are taking
Histafix even as we speak, so we should ban it now so that these people
can be cured of their dependence on Histafix.
Kiersten. Um, maybe all these people keep taking Histafix because their allergies don't magically go away after they take a few doses.
Exercise 10. Tate. I just found out that exposure
to Faux News causes blowhardery. It's been found that the more time
people spend watching Faux News Network, the more likely they are to
become irrational, fact-avoidant, gratuitously insulting pompous,
Kelsie. That's rubbish. I know hundreds of
blowhards who never watched Faux News, so blowhardery has nothing to do
with watching that Fair And Balanced network
Exercise 11. Mike. Gasolene is flammable, so I don't think it's a good way to put out that fire.
Karley. The need to pour gasoline on the fire has
never been so clear. Ever since I started putting gasoline on the fire
it's been getting fiercer and fiercer! So obviously, we need to go out
and buy a lot more gasoline.
Exercise 12. Barry. I used to think that Reverend
Jim was wasting his time with his Pray for Peace campaign, but it's
really begun to foster a sense of community in our parish.
Julius. A sense of community is a good thing, but
we must set it against the needs of people in other countries. Since
Reverend Jim started his Pray-For-Peace campaign, four more wars have
started. We must shut down this Pray-For-Peace campaign before even more
countries are dragged into war!
Exercise 13. Wally. If we allow pornography in
adult book stores it won't stop there. Soon it will be in the regular
book stores, because they're book stores too. Then it will be in the
libraries, because they're just bookstores that lend books instead of
selling them. Schools have libraries, so it will soon be in the schools
too! Well did you know that churches have schools too, so if we allow
pornography in adult book stores it won't be long before it's in our
churches too! Obviously, pornography should be banned absolutely
Xena. The people who want to ban pornography are
mostly the same people who want to ban all discussion of sex. If we cave
in on pornography they'll have a precedent to point to, which will make
it easier for them to ban things like The Joy of Sex. If they succeed
there, they'll go on to other things, like sex education. If we want to
preserve free discussion of sexual matters, we should hold the line on
Exercise 14. Augustus. I really think that the
government should put more money into discouraging cellphone use.
Cellphones produce microwave radiation, so using a cellphone is
literally holding a radiation source right next to your brain. Radiation
causes cancer, so it is insane to routinely expose the most important
organ in your body to a known carcinogen several times a day. Millions
and millions of people use cellphones on a daily basis, so if cellphones
cause cancer these people are at a serious risk. We cannot wait for
research because waiting could potentially allow thousands of people to
contract deadly brain cancers.
Fred. Wait a moment. Cellphones have been around
for years and years, so if they caused cancer we would already see a
rise in the cancer rates, and this rise would include a correlation
between cancer and cellphone use. This is exactly how we found out that
cellphone use causes car accidents. There is no rise in the cancer
rates, and cancers are not correlated with cellphone use, so cellphone
use is not a significant cause of cancer.
Exercise 15. Cullen. I think it's pretty clear
that drinking bottled water causes mopery. A recent study has shown that
people who drink bottled water are four times as likely to mope around
as people who don't drink bottled water.
Sterling. Yes, but the study also showed that
there's plenty of people who mope around without ever touching bottled
water, so the study doesn't prove that drinking bottled water causes
Exercise 16. Quentin. I think we should go back to pumping oxygen into that sunken submarine. It would help the sailors.
Elisha. Since we stopped pumping oxygen into that
sunken submarine the sailors have gotten sicker and sicker. This is a
very serious situation which we must address immediately by making sure
that there is absolutely no oxygen in that sunken submarine.
Exercise 17. Tanya. I've just heard some
disturbing news. A major recent study just compared two demographically
identical groups, one of which listened to classical music a lot, and
the other didn't listen to classical music at all. The group of
classical music listeners turned out to have a much higher percentage of
white-collar criminals than the non listeners, so it looks like
listening to classical music causes white-collar crime.
Alfred. I've seen the same study, and I can tell
you that it totally fails to prove that classical music causes
white-collar crime because nowhere in that study do they even begin to
explain how listening to classical music goes about causing that
Exercise 18. Roland. Statistics show that once
people start using a sunscreen, they almost never go back to sunbathing
without it. So obviously use of sunscreen makes people dependent on
sunscreen. Since it is bad for people to be dependent, we should abolish
Vilma. Doesn't it occur to you that people continue
to need sunscreen because strong sunlight continues to contain
dangerous ultraviolet radiation?
Exercise 19. Humberto. It's beginning to look like
drinking herbal tea makes people taller. They did a long-term study
comparing a million adult herbal tea drinkers with a million adults who
never, ever drink that disgusting rubbish. On average, the people in the
herbal tea group got three millimeters taller for every year they drank
herbal tea, while the demographically equivalent adults in the other
group didn't grow at all.
Camila. Herbal tea doesn't make people taller. Plenty of people in that study drank herbal tea for years without getting any taller.
Exercise 20. Answer the following questions, and explain your answers.
i. Are causal arguments required to explain how the purported cause causes the effect?
ii. Are causal arguments required to show that the purported cause is the only thing that ever causes the effect?
iii. Are causal arguments required to show that the purported cause absolutely always causes the effect?
iv. Can a causal argument succeed without showing that the purported cause is at least sometimes correlated with the effect?
v. Can a causal argument be based on a "cause" that hasn't been previously proved to exist?
vi. Can a causal argument be based only on the fact that the "cause" is always absent whenever the effect is absent?
vii. Can a causal argument work if something else is just as strongly correlated with the effect as the purported cause?
viii. Can a causal argument be based on anecdotal evidence?
ix. Does the "cause" have to have a one-to-one correspondence with the effect?
x. Is "it's the only thing I can think of" ever a good causal argument?
Exercise 21. Answer the following questions, and explain your answers.
i. Is it possible to make a successful causal argument without any
evidence of a correlation between the effect and the thing that’s
supposed to be causing it?
ii. Is it possible to make a successful causal argument without
providing an explanation of how the purported cause might cause the
iii. Is it possible to make a successful causal argument without providing any evidence that the purported cause even exists?
iv. Is it possible to make a successful causal argument if it is
proven that the purported cause sometimes happens without being followed
by the effect?
v. Is it possible to make a successful causal argument based on a single incident?
vi. Is it possible to make a successful causal argument if it is
proven that the effect sometimes happens even though the purported cause
is not present?
vii. Is it possible to make a successful causal argument based only
on the fact that no-one else can think of anything that could cause the
The key to exercises 1-4 is to work out your own answer first and
then compare your reasoning to the arguments given in the exercises. If
your answer is better supported, then the argument in the exercise is
1. Daryl’s argument misses the fact that the patients who didn’t
fairy-up also took Zydigm. (Gwendolyn alludes to this in her criticism
of Daryl’s argument.) However, the real problem is that there is one
drug, Xindeco, that was only taken by the fairies. This means that
Mill’s method of difference supports Xindeco as the cause, not Zydigm.
(It is also possible, but less likely, that this is a coincidence, and
that one of the other drugs causes the problem, but only in some
2. Aliya’s argument is weak because she ignores the fact that Dasia
got laser eyes without taking Terraplex. It’s possible that both
Terraplex and another drug cause laser eyes, but it’s not likely. Mill’s
method of agreement much more supports the claim of Shegos to be the
cause because it is the only drug taken by all four patients.
3. Gianni fails because his “1-to-1 correlation” is not a
correlation at all, as Susana points out. The fact that a one-general
patient took exactly one milligram is meaningless because “milligram” is
an arbitrary measure. If the drug had been measured in “grains” (an old
apothacary’s standard) it’s mass would have been 64.79891 grains.
Susana is right that we have to look for what Mill calls “concommitant
variation,” and we find it in Kolvox, which gives us one channeled
general per 50mg.
4. Zoie fails because she does not correctly apply Mill’s combined
method. If you examine the evidence you will see that there is one and
only one drug that is always present when extra limbs are present and
always absent when extra limbs are absent, and that drug is Quindor.
5. It’s the mineral water. It’s the only thing that correlates with
the asthma. As the villagers began drinking it more and more, the
problem got worse and worse. If it was the tin mine, the asthma problem
would have started in Roman times and continued at the same level since
then. The bats have been around longer than the tin mine, even though
they were only discovered in 1845, so it’s not them either. The perfume
factory shut down during both wars and the wheat only produces pollen in
the summer, but the asthma problem didn’t go away during either war,
and it exists even when there’s no pollen in the air, so neither of
those is the cause. consumption of the mineral water is the only thing
that perfectly correlates with the asthma problem, so it’s the cause.
6. Raegan appears to be relying on the idea that homefront protests
encourage the enemy to fight harder which endangers the combat troops.
and it does seem reasonable that if the German people had protested the
1939 invasion of Poland, the Poles might have been encouraged to more
strongly resist the blitzkrieg. The same applies for other Saddam
Hussein’s 1990 invasion of Kuwait, and so on. In fact, if Mexico fell
into the hands of an aggressive right-wing government that somehow
managed to mount a successful invasion of the US, protests against this
invasion by ordinary Mexicans would probably encourage Americans to more
strongly resist the invasion, thus endangering the Mexican soldiers
spearheading the invasion. Of course, if the invading government changed
it’s mind and stopped the invasion, none of the soldiers would be in
any danger at all, so if Raegan really cares about the troops lives, she
should also be trying to stop the invasion.
7. Savanah is wrong because Glenn is only claiming that dancing
makes knobby knees more likely, not that it always causes knobby knees.
8. Leila’s argument doesn’t work because a causal argument only
needs to prove the existence of a reliable correlation between two kinds
of event. The lack of explanation doesn’t matter so long as the
correlation is proved. (Pretty much all known causal relationships
lacked explanation when they were first proved.)
9. What would it mean to say that someone is “dependant” on
something? Presumably it means that the person finds himself unable to
do without that thing even though he actually had no real need for that
thing. Thus someone who is dependant on Histafix would be unable to stop
taking Histafix, even though she actually did not need it to control
allergy symptoms. To make his argument work, Everett would have to show
that there is a significant group of people who provably do not have
allergies, and who still find themselves unable to do without Histafix.
Since he fails to even begin to prove the existance of even one person
who both lacks allergies and stays on Histafix anyway, Everett’s
argument fails completely.
10. Kelsie’s argument fails. Tate is not claiming that exposure to
Faux News is the only cause of blowhardery, only that it is a cause. It
is perfectly possible for there to be more than one cause of
blowhardery, so the existance of non-Faux blowhards doesn’t invalidate
11. Karley has reversed the direction of effect. She wants the fire
to go down, and advocates adding gasolene to achieve this, but the
addition of gasolene positively correlates with the fire getting
fiercer, not with it going down. Notice that while Mike does not support
his claim that gasolene is flammable, this is okay because that claim
is commonly accepted and not challenged in this dialog, whereas Karley
actuall cites evidence that contradicts her conclusion.
12. Barry and Julius make unrelated causal arguments. Barry simply
claims that Rev. Jim’s Pray for Peace campaign has begun to foster a
sense of community. This could presumably be challenged in various ways,
but Julius does not do so. Instead, Julius points out that four more
wars have started since the campaign began. However, he does not say how
many wars ended, or how many began before the campaign got going, and
he ignores all the other possible causes of those four new wars.
13. Both Wally and Xena attempt to make causal chain arguments. Such
arguments only work if each link in the chain is a proven causal
relationship. Wally’s argument is based only on his own definitions, so
isn’t based on causal relationships at all. This makes it a definite
slippery slope fallacy. Xena’s argument, in contrast, is based on claims
about the real nature of the issues and the people involved and so if
her description of the situation is accurate, her argument is at least
14. The first thing to notice that Augustus has not produced
evidence of any correlation between cellphone use and cancer. Instead,
his argument is based on what happens in an only vaguely similar
situation. This is not a correlation based argument and so, although it
is intended to support a causal claim, it is not really a causal
argument. Augustus’s argument is based on the solidly proven link
between radation and cancer, but he does not discuss the levels of
radiation involved in cellphones. This is important because below a
certain exposure level, microwave radiation is basically harmless. (We
will discuss this argument again in the section on analogy arguments.)
Also notice that Fred’s argument is based on a demonstrable lack of
evidence, and we will discuss this kind of argument later also.
15. Sterling is wrong. Cullen is just arguing that drinking bottled
water causes mopery, not that it is the only cause of mopery.
16. Elisha is reversing the direction of effect here. his evidence
supports the claim that it is a lack of oxygen that is making the
17. Alfred fails. If you can show a solid correlation, you’ve proved
the causal relationship. You don’t have to be able to explain something
in order to prove that it exists.
18. Roland does not prove that anyone is dependant on sunscreen,
only that people continue to use suncreen over long periods of time.
That’s not dependance. To prove that sunscreen causes dependance, he
would have to prove that sunscreen dependance exists and is correlated
with sunscreen use. He hasn’t done that, so his argument doesn’t work.
19. Humberto does not have to prove that herbal tea always make people taller, only that it sometimes does.
iv. Well, no.
v. Good god, no!
vi. No way.
vii. No. Are you kidding?
ix. Ha! No.
x. Don’t make me laugh!
(All answers are "no.")
If you need to make up the quiz for this chapter, use the Make Up Exercise
Copyright © 2009 by Martin C. Young
This Site is
Proudly Hosted By.