RECOGNISING IMPLICATIONS OF ARGUMENTS

Sometimes a whole argument has implications which go beyond the particular subject
with which it is concerned. There are two important ways in which an argument can do
this – by exhibiting a particular structure or shape, which it can have in common with
arguments on other topics, or by relying on a general principle which can be applied to
other cases. The skills involved in dealing with implications of arguments can be described
as recognising parallel arguments and recognising and applying principles.
Recognising parallel arguments
The value of this skill is that being able to recognise parallel arguments may help us to see
what is wrong with an argument. Sometimes it is easier for us to recognise a flaw in an
argument if the argument is about a familiar subject. Suppose you are presented with an
argument on an unfamiliar topic, and although you doubt your ability to assess the subject
matter, you can nevertheless see that the argument has a particular shape or pattern. If you
can substitute some familiar subject matter into this pattern, you may be able to see
whether the argument is good. Not all arguments can be dealt with in this way; those
which can tend to be relatively short, and to succeed or fail in virtue of their structure,
rather than because there is additional evidence which counts against them.

Someone who objects to an argument by saying ‘You might as well argue that . . .’ is often
presenting a parallel argument to show that there is a problem with the original argument.
This is what is happening in the two following examples of conversations:
James: I mean what I say because I say what I mean.
John: You might as well argue that you eat what you see because you see what you eat.
Sam: We have all had the experience of being deceived by our senses – the stick
which looks bent when it is straight, and so on – and all the information we get
through our senses in this way is potentially illusory, therefore sense experience
is always unreliable.
Jo: You might as well argue that since we’ve all had the experience of being lied to
– that even lovers lie and that everyone is potentially untrustworthy, therefore
no one can ever be trusted.
The argument presented in Exercise 5 (p.22) offers an example in which, if we construct
a parallel argument, we can see that an unwarranted inference has been made. The
argument concerned the claim that there is no justification for public discussion and
condemnation of the sex life of the US President. In order to persuade us that a husband
who deceives his wife can nevertheless be a good President, it gave examples of Presidents
who had been good husbands (in the sense that they did not deceive their wives) but bad
Presidents. We could summarise this section of the argument as follows:
Someone who does not deceive his wife can nevertheless be a bad President. So
someone who does deceive his wife can be a good President.
Although the conclusion here may be true, and although – especially if we agree with the
conclusion – we may be tempted to think that a good reason has been offered for it, in fact
the first sentence is not a good reason for accepting the conclusion.
This is evident if we look at the following parallel argument:
Someone who is not cruel to children can nevertheless be a bad child minder. So
someone who is cruel to children can be a good childminder.
We can immediately see with this example that the conclusion cannot be true, because
someone who is cruel to children cannot possibly be a good childminder. If the conclusion
must be false, then this cannot be a good argument even if the reason offered is true. The
reason no doubt is true, because in order to be a good childminder you have to do more
than merely refrain from cruelty to children. The argument is bad because the reason is
not sufficient to establish the conclusion, and if this is so with the argument about
childminders, then it is also the case with the parallel argument about US Presidents.
Whether or not a President who deceives his wife can nevertheless be a good President
depends upon whether the tendency to deceive extends to all areas of the President’s life. It
does not depend upon whether a President who is an exemplary husband deceives the
public about some of his actions.
Exercise: Identifying parallel arguments
In these multiple choice questions, you should pick the answer which uses reasoning
parallel to the reasoning in the original passage.
1 Because heroin addicts usually have one or more needle marks on their arms, and
Robert has some needle marks on his arm, it follows that Robert is probably a heroin
addict.
Which of the following most closely parallels the reasoning used in the argument
above?
(a) Because patients with malaria usually have high fevers, and George is a patient
with malaria, George probably has a high fever.
(b) Because patients with malaria usually have high fevers, malaria probably causes
high fevers.
(c) Because doctors have high incomes, and people with high incomes pay high
taxes, doctors probably pay high taxes.
(d) Because students are usually under twenty-five years old, and Harold is under
twenty-five years old, Harold is probably a student.
(e) Because heroin addicts usually have needle marks on their arms, most heroin
addicts probably inject the drug directly into their veins.
(Law School Admission Test, February 1986)
2 It has usually been claimed that in eras of high infant mortality, parents adopted
indifference to children as an emotional defence. But some scholars deny that parents
were indifferent to children because so many died, arguing instead that the children
died because their parents were so unconcerned about their children as to spare no
time for them.
Which of the following is most similar in its structure to the argument described in
the last sentence above?
(a) It was not the school’s new reading programme, but parents’ increased concern
with their children’s schoolwork that produced better reading scores.
(b) It is not true that the lack of qualified workers depresses wages in the poor
sectors of an industrial economy; rather, the low wages attract unskilled labour.
(c) It is not changing demand that prompts the introduction of new fashions;
actually the clothing industry brings in new fashions whether the public wants
them or not.
(d) It is not true that those who take illegal drugs harm only themselves; by supporting
organised crime, they harm society as well.
(e) It was not considered worthy of a poet to write for the Elizabethan theatre;
nevertheless, many poets did so.
(Law School Admission Test, June 1983)
3 The achievement of zero population growth in Great Britain has not forestalled the
recent political and economic decline of Great Britain. We must conclude that rapid
population growth is not the economic disaster social scientists have led us to believe
it to be.
Which of the following is most like the argument above?
(a) Many people who do not smoke cigarettes develop chronic respiratory illnesses;
therefore, cigarette smoking cannot be the health risk it is supposed to be.
(b) Jerry bought expensive paint but she still had to apply two coats to the wall to
cover the old colour; therefore, you might as well buy the cheapest paint available.
(c) Even if the country uses less energy this year than it did last year, more oil will
be imported than was imported last year; therefore, energy conservation should
be encouraged.
(d) This drug causes certain side effects in a small percentage of the population; we
can conclude that it is safe for the majority of people.
(e) Some of his paintings are dull and uninspired; we can conclude that he is not in
the same class as the greatest artists.
ANSWERS:

Recognising Implications: Assessing implications

Exercise:
For each of the following passages, assume that what is said in the passage is true, and
assess whether each of the responses (a) to (e) is true, false, probably true, probably false,
or whether you have insufficient information in the passage to draw any conclusion about
the statement’s truth or falsity. Write your answer – T, F, PT, PF, or II – at the end of each
of the sentences (a) to (e). You may find it interesting to compare your answers to the
exercise with someone else’s.
1 A study from Sweden reports that the incidence of skin cancer increased by 50 per
cent between 1979 and 1987. Exposure to sunlight is known to cause skin cancer in
light-skinned people. The incidence of skin cancer was found to be higher amongst
professionals than amongst manual workers – thus it was higher amongst those who
can afford to take holidays in places with very sunny climates. Twenty per cent of
skin cancer cases occurred amongst those aged between 20 and 39, although most
types of cancer are uncommon in this age group.
(Source: ‘Cancer threats all around us’, Celia Hall, The Independent, 30 March, 1993)
(a) Manual workers in Sweden have no risk of getting skin cancer.
(b) There is a lower risk of skin cancer for those aged over forty than for those aged
under forty.
(c) The increase in the incidence of skin cancer in Sweden indicates that exposure
to sunlight cannot be the only cause of skin cancer.
(d) Those aged over 40 in Sweden are more likely than the rest of the population to
take holidays in places with sunny climates.
(e) The increased incidence of skin cancer in Sweden may be due to an increase in
the numbers of people taking holidays in places with sunny climates.
2 Nearly 600 people, most of whom had an inflated sense of their own safety as car
drivers, took part in a study which investigated ways of getting people to drive more
safely. The drivers were asked to fill in a questionnaire detailing an imaginary
accident which they had caused and which had serious repercussions, such as the loss
of a child’s life. They had to write a description of the consequences, and imagine
the subsequent guilt, lack of confidence or inability to drive again. Before the study,
50 per cent of the group said they would be prepared to drive at over 80 miles per
hour on a motorway. After completion of the questionnaire, this figure fell to
27 per cent. The group most likely to overestimate their driving skills and safety were
young men.
(a) Most drivers have an inflated sense of their own safety.
(b) Some drivers who overestimate their driving skills tend to drive too fast.
(c) People with only a few years driving experience do not overestimate their skills.
(d) Forcing drivers to imagine that they have had a serious road accident may make
them drive more responsibly in the future.
(e) Imagining that one has caused a serious accident has the undesirable effect of
reducing one’s confidence as a driver.
3 A technique for inducing phantom sheep pregnancies has been developed to address
the problem of what to do with the million lambs born each year to mothers that for
one reason or another cannot breast-feed them. Fostering is notoriously difficult
because a ewe quickly forms a bond with its own lamb and rejects all others. Farmers
are forced to rear orphaned lambs themselves, and lack of maternal contact can cause
behaviour abnormalities. Gently stretching the neck of the cervix with two fingers
sends nerve signals to the animal’s brain that mimic those produced in labour. The
sheep believes it has given birth to a second lamb. The orphaned lamb can then be
introduced to its new mother with an 80 per cent chance that it will be accepted.
(a) A ewe which gives birth to two lambs from one pregnancy will form bonds with
both lambs.
(b) A ewe will reject her own lamb if she is introduced to an orphaned lamb.
(c) An orphaned lamb may fail to develop normal behaviour if it is not fostered by a
ewe.
(d) An orphaned lamb needs maternal contact in order to grow to adulthood.
(e) The formation of a bond between a ewe and a lamb can occur even if the ewe is
not the mother of the lamb.
4 Dipping of sheep protects the animals from scab and blowfly attacks. Leather manufacturers
report that since sheep dipping ceased to be compulsory last year, 60 per
cent of British sheepskins have been found to have damage from these parasites. But
there are worries that sheep dips can cause health problems for farmers who use
them. The Veterinary Products Committee examined medical evidence on 266 cases
of people who believed that their influenza-like symptoms were caused by exposure
to sheep dip. They found a possible link to sheep dip in only fifty-eight of these cases,
and of these fifty-eight, only three had worn protective clothing while using the dip.
The long-term effects of low level exposure to sheep dip are not known. However,
because of concerns about safety, the Ministry of Agriculture has introduced legislation
requiring farmers who use sheep dips to have a certificate of competence.
(a) Scab and blowfly cause distress to sheep.
(b) There is no evidence that there may be a link between influenza-like symptoms
and the use of sheep dips.
(c) Protective clothing prevents sheep dip from damaging farmers’ health.
(d) Low level exposure to sheep dip is known to be dangerous enough to justify
banning the use of the dip.
(e) Sheep dips need to be handled with great care because they present a risk to the
health of farmers who use them.
5 In 1963 Stanley Milgram investigated whether people would obey orders when they
were asked to do something which conflicted with their moral attitudes. Volunteers
for his experiment were made to believe that if they pressed a button, they would
administer an electric shock to a ‘learner’ seated behind a screen, who was giving
answers in a memory test. The subjects were ordered to press the button every time
the ‘learner’ gave a wrong answer. The ‘learner’ did not receive a shock, but cried out
as if in pain each time the button was pressed. Contrary to the predictions of psychologists,
most of the subjects in the experiment continued to obey the order to press
the button, even though they expressed anxiety about doing so.
(a) The volunteers for the experiment were not typical of people in general.
(b) Those who took part in the experiment wanted to avoid inflicting pain.
(c) There is no evidence that people will obey orders when asked to do something
they consider wrong.
(d) Those who took part in the experiment did not believe that the ‘learner’
suffered any pain.
(e) Prior to the experiment, psychologists had thought that most people would
refuse to obey an order to give electric shocks.
6 The red squirrel has been pushed out of most of its territory in Britain by the North
American grey squirrel which was introduced at the end of the nineteenth century.
This is probably because grey squirrels can digest acorns (an ability that evolved in
their native woodlands where oak trees are common), whereas red squirrels, which
normally live in conifer woods, eat acorns only reluctantly, and lose weight on a diet
that consists solely of acorns. When red squirrels do not have to compete with grey
squirrels, hazelnuts are a major item of their diet throughout the winter. Grey
squirrels eat acorns only after all the available hazelnuts have been consumed. Where
grey squirrels are plentiful, they have often eaten the entire crop of hazelnuts by
October.
(a) Red squirrels are not found in North America.
(b) Grey squirrels will eat anything that red squirrels eat.
(c) Red squirrels would thrive in woodland that contained only oak trees.
(d) Grey squirrels would not survive in woodland in which there were no
hazelnuts.
(e) In woodland in which both acorns and hazelnuts are found, grey squirrels are
more likely to thrive than are red squirrels.
ANSWERS:

Recognising Implications:DRAWING CONCLUSIONS

One important aspect of reasoning is the ability to go further than the information you
have been given, to draw conclusions from evidence, to see what follows from statements
which other people make. This is an ability which we all exercise to a certain extent in our
daily lives. If we draw back the curtains in the morning, and find that last night’s snow
covering has gone, we conclude that the temperature must have risen overnight. If we
know that a friend has completed a 150 mile car journey in two hours, we conclude that
they must have exceeded the 70 mph speed limit.
Sometimes our conclusions will be more tentative than in these two examples. If we know
that a colleague’s children have all had bad colds recently, and we hear that colleague
sneezing throughout the day, then it is reasonable to conclude that they have caught a cold.
But they may not be suffering from a cold. Perhaps their sneezing is caused by an allergy to
something in the office, for example, a new pot plant or a new type of printing ink. In cases
like this, where the evidence points to a conclusion which may need to be reconsidered
in the light of further evidence, it is best to express our conclusion as something which is
‘probable’ or ‘likely’.
To improve our capacity for critical reasoning, we need to exercise the ability to draw
conclusions in a systematic way whenever we are presented with information – in discussions
with others, when reading newspapers and textbooks, when listening to the
comments of politicians. We may find it easiest to draw conclusions about those subjects
with which we are most familiar, but with practice, we can make progress in improving
the ability in relation to less familiar topics.
Let us turn to some examples to illustrate this. Consider the following passage:
Men with low blood cholesterol levels are more likely to develop intestinal cancer
than those with high blood cholesterol levels. But men who have high blood
cholesterol levels have an above-average risk of suffering a heart attack.
What conclusions can be drawn from this information? Can we conclude that it would be
a good thing for all men to aim to have a low blood cholesterol level, on the grounds that
this would reduce their risk of suffering a heart attack? No, we cannot conclude this from
the information available, because if they achieved a low blood cholesterol level they
would be more likely to develop intestinal cancer. So the most which can be concluded is
that lowering a patient’s blood cholesterol level in order to reduce the risk of heart attack
may increase the patient’s risk of intestinal cancer, and thus that it may not be wise to
attempt to lower a patient’s blood cholesterol level.
Note the tentative nature of this conclusion. It is possible that further information may
lead us to revise the conclusion. Suppose that intestinal cancer is a disease which usually
occurs in old age. In that case, lowering someone’s blood cholesterol level may move them
out of the group likely to die relatively young from a heart attack, and into the group likely
to live much longer, but also at risk of – eventually – developing intestinal cancer. In that
case, it may be wise to attempt to lower the blood cholesterol levels of those likely to suffer
heart attacks.
Let us look at another example:
Repeated spraying with the insecticide did not rid the tobacco fields of the insect.
Only the strongest of the species survived each spraying. When they mated, they
produced offspring more resistant to the insecticide than they were.
(Law School Admission Test, June 1983)
What can be concluded from this information? We know that the insects which were
strong enough to survive repeated spraying with insecticide produced offspring with even
greater resistance to the insecticide. In the original population of insects, there were
obviously some with weak resistance and some with strong resistance, so perhaps it is just a
matter of chance whether a particular insect has strong or weak resistance, and therefore
just a matter of chance that the offspring of the survivors had strong resistance.
But if it were just a matter of chance, then we should expect the new generation to include
some insects with weak resistance to the insecticide. The fact that they all had strong
resistance suggests that there is something about being the offspring of those with strong
resistance which makes insects more likely to have strong resistance. And this suggests that
resistance to insecticide, in at least some species, can be passed from one generation of
insects to the next. This is a useful conclusion to draw because it tells us that repeated
spraying with insecticide may not have the effect of eventually eliminating insect pests. It
may even have the effect of making the insect population stronger, if those which have
the resistance to the insecticide are strong in other respects as well, for example, in their
abilities to reproduce or to withstand adverse weather conditions and disease.
Here are some exercises for you to practise your skill in drawing conclusions.
For each of the following, say what conclusion you can draw from the passage:
1 The pond is frozen this morning. It was not frozen yesterday.
2 There is a flu epidemic sweeping through the school. Gitta, one of the pupils, has a
very high temperature and aching muscles, both of which are symptoms of flu.
3 The winter has been very severe. When we have a severe winter, the daffodils usually
come into flower late.
4 Jane arrived before Jim, although they set off at the same time, and they were both
travelling by car.
5 The murder victim died at 9 p.m. on Saturday. It is suspected that he may have been
poisoned, but it is not yet known whether it was poison or the blow to his head which
killed him. The injury to the head would have caused death instantly, had he still
been alive when he was hit. It has now been discovered that Ms Brown, the chief
suspect, was with friends 5 miles away from the murder scene between 7 p.m. and
10 p.m. on Saturday.

Practising the skills

Identify and evaluate the reasoning in each of the following passages.
1 Fluoride dangers
Sir: I was concerned to read of the proposals for compulsory fluoridation of water.
Fluoride is a medication and one with well-reported side effects, such as increased
incidence of osteoporosis. Those not wealthy enough to afford water filtering systems
will be forced to consume it; the dose will not depend on any perceived ‘need’
but on the amount of water consumed: I get through up to seven litres a day so my
dosage would be up to 14 times that of many people.
Additionally, the measure merely serves as a temporary cover for the real problem –
that of sugar consumption; it is not unfluoridated water but sugar which causes
tooth decay; it also causes diabetes, immune system impairment and obesity.
Fluoridation therefore merely enables people to salve their consciences in the short
term regarding bad diet and to do themselves long-term damage; it is like shooting
the miner’s canary.
It is a civil liberties issue; if fluoride, why not any other medication? It is frightening
to think that this question is even being raised.
(Karen Rodgers, Letters to the editor, The Independent, 11 September 2003)
2 Organic farming
Sir: Those who believe organic food is good for the countryside and the environment
should think a little harder.
Organic yields are significantly lower than intensive yields. To grow the same
amount of food, organic farming therefore requires land that could otherwise be
used for nature reserves, forests or wetlands – or golf courses and low-cost housing
if we so choose. To irrigate the additional land more water is required, reducing
rivers and aquifers. Moreover, since organic farms still use tractors, water
pumps, harvesters and other fossil-fuel powered implements, and these have to
travel over a greater area to produce a given quantity of food, they produce higher
CO2 emissions.
As for farmers’ markets, consider what would happen if the eight million people in
London were forced to drive out to rural areas to source their food – not only would
there be chaos, but also the resultant emissions from cars would dwarf the emissions
of the relatively few large lorries that currently bring food to supermarkets in town
and the short car journeys we make to the supermarket.
Since energy and land are both costs, the market will ensure structures that make
the most efficient use of both. Organic farming does the reverse, to the detriment of
all.
(Tim Hammond, Letters to the Editor, The Times, Thursday 11 January 2007)
3 Extract from ‘Television – a force for good in our
nation’s prisons’
. . . it would be mad for Mr Straw [the Home Secretary] not to proceed with the
proposal to unleash the BBC and commercial TV companies on the prison population.
It is the right thing pragmatically and in principle too.
Why? First because of what British prisons are like. In the main, they are grossly
overcrowded, very uncomfortable already and constant hives of crime-behind-bars.
Men who are left with nothing to do, many of them being illiterate, currently amuse
themselves with drugs, sex, constant little vendettas and a little light violence.
Because of overcrowding, they spend more and more time in their cells. Is ‘Have
We Got News for You’, or ‘Casualty’ or ‘Brookside’ really a worse alternative than
cannabis and recreational buggery? Furthermore, increasingly, television means
communication with the rest of us, albeit one-way communication. For the modern
citizen, TV is the ubiquitous window on society, a prime source of thinking and
information. It shapes us. Now, granted, prisoners are physically cut off from society,
but that is as much for our safety as for their punishment. Assuming that we
hold to the idea of rehabilitation and the return of prisoners to ordinary life after
their sentences, then cutting them off from social trends, thinking, entertainment
and news is pointless, even stupid. Prisoners who watch television for hours are not
only likelier to be easier to guard and oversee; they are also likely to end up more like
the rest of us.
The second reason we approve of television in jails is that inmates would not be
given them free, but would have to pay for the privilege, using money earned inside
jail. TVs would be removed for bad behaviour. Prison is such a bizarre and alienating
environment that anything which keeps inmates in touch with ordinary life is
useful; earning and paying is useful because it increases, however marginally,
responsibility. It is what prisoners will quickly have to learn to do outside.
This is, in short, a proposal which is sensible in security terms, mildly rehabilitative
and – yes – humane.
(David Aaronovitch, The Independent, 30 November 1997)
4 Extract from ‘The economic case for drugs’
America spends at least $20 billion (£13 billion) a year on drug enforcement, and
arrests more than one million people a year on drug charges. Yet, according to
standard economic analysis and existing evidence, drug legalisation would be a far
superior policy to drug prohibition.
Drug prohibition does not eliminate drug markets or drug use; it simply moves
them underground. Prohibition raises some costs of doing business for drug
suppliers, and it probably reduces demand by some consumers.
But substantial drug consumption persists even in the most repressive prohibition
regimes. Data in the US suggests that more than 30 per cent of the population aged
12 and over has used marijuana, and more than 10 per cent has used cocaine.
Violation of prohibition is widespread.
Prohibition increases violence, because buyers and sellers of drugs cannot use the
official justice system to resolve disputes. Prohibition also plays a key role in nonviolent
kinds of crime, by diverting criminal justice resources from the deterrence of
non-drug crime. It facilitates the corruption of police, judges and politicians, partly
because huge profits are at stake, partly because the legal channels of influence are
not available.

EVALUATING REASONING: THE NECESSARY SKILLS

The skills discussed in this chapter need to be used together when assessing a passage of
reasoning. We need to consider whether the reasons, and any unstated assumptions, are
true; whether anything which we ourselves know, but which is not stated in the passage,
weakens or strengthens the conclusion; whether, if the passage relies upon an explanation,
we can think of equally plausible alternative explanations; and finally whether we can
identify flaws in the reasoning which show us that the conclusion is not well supported by
the reasons. We also need to consider whether the argument relies upon evidence from
anyone whose authority is questionable. This is discussed in detail in Chapter 4, which also
contains exercises on evaluating evidence and authorities. Meanwhile, here is a summary
of the skills discussed in this chapter, followed by an exercise in applying these skills to
some slightly longer arguments.
Summary: Using the skills of evaluation
1 Find the conclusion.
2 Find the reasons and any unstated assumptions.
3 Consider how far you can go in assessing the truth of the reasons and the
unstated assumptions. Think about how you would seek further information to
enable you to assess the truth of reasons.
4 Do you have any knowledge which strengthens or weakens the argument?
(Remember to subject your own ‘knowledge’ to the same standards of scrutiny
as you apply to the claims made by others!)
5 Does the passage contain any explanations? If so, are they plausible, and are
they the only plausible explanations of what is being explained?
6 If you believe that the conclusion is not well supported by the reasons and
assumptions, can you state the way in which the move from reasons to
conclusion is flawed?

Identifying and evaluating explanations

In each of the following five passages, an explanation is offered, or various different
explanations are considered, for a given fact or phenomenon. For each passage:
(a) identify the fact or phenomenon which is to be explained;
(b) find the explanation or explanations given in the passage;
(c) think of any other possible explanations which are not mentioned in the passage;
and
(d) either
i. say which explanation you think is the most plausible, and why; or
ii. suggest further evidence you would need in order to decide which explanation
is the most plausible.
This exercise could form the basis of a class discussion.
1 Girls doing well while boys feel neglected, study finds
Donald MacLeod
‘Boys are blamed for everything’, complained a 14-year-old, encapsulating the
jaundiced view of school that seems to be having such a bad effect on boys’ exam
results.
‘It was a myth that girls perform poorly at school’, said Michael Younger, whose
study of an East Anglian comprehensive elicited the 14-year-old boy’s comment.
Boys are the problem.
The boy also complained: ‘Girls are treated a lot better and get first choice of
equipment and task.’
Reflecting the national picture, the girls at this school have done consistently better
at GCSE than the boys, although the gap has narrowed.
Mr Younger said some schools should take credit for implementing equal opportunities
policies which had reduced discrimination against girls. They now had to tackle
boys’ under-achievement and disengagement, although Mr Younger admitted that it
was a complex problem to which he did not have any easy answers.
He and Molly Warrington, his fellow researcher at Homerton College, Cambridge,
found that boys felt they were unfairly treated or neglected in class, although
teachers and the majority of girls disagreed.
Staff said boys went to considerable lengths not to appear swotty – for instance,
denying to classmates they had done homework even when they had, or playing up
in class. They saw boys as unable to concentrate or organise themselves and lacking
in motivation.
Girls tended to be more focused, and study was not seen as bad for their image.
Parents and teachers agreed that girls did more homework, while boys saw it as a
necessary evil to be done as quickly as possible.
Seventy per cent of girls thought female teachers treated boys and girls equally; only
46 per cent of boys agreed.
A majority of all the pupils surveyed thought male teachers were biased towards
girls, however – accepting behaviour from girls which they punished in boys.
A fifth-form girl agreed that girls were treated more leniently by male teachers. ‘The
girls have a reputation for being well-behaved, so if, for example, they don’t do their
homework they won’t get told off as much.’
Boys from the same year complained that they got less attention from male teachers
than the girls did.
Girls appeared to have clearer goals, said Mr Younger, which led them to focus on
their work. Some boys had no idea what they wanted to do after GCSE and several
had no idea what later courses to take.
(Copyright Guardian News & Media Ltd 1995)
2 Number of road deaths at post-war record low
Fewer people were killed on Britain’s roads last year than in any year since 1926, but
a rise in the number of those seriously injured suggests that further improvements
are unlikely.
Preliminary figures released by the Department of Transport suggest that 3,651
people died on the roads, a fall of 4 per cent compared with 1993 when 3,814 died
– the previous post-war record low.
The fall in deaths, despite an increase in road traffic of 3 per cent, appears to be
explained by better paramedic treatment at the roadside and improved medical care,
since the figures for serious injuries have increased to 46,784, a rise of 4 per cent.
In fact the number of deaths is just about the only figure to have gone down between
1993 and 1994. Serious injuries for both car users and pedestrians also increased.
Indeed pedestrian casualties rose by 2 per cent overall from 1993 levels to 49,026
and while deaths fell by 7 per cent to 1,148, serious injuries increased by 4 per cent
to 11,924.
While Britain generally has a good safety record on the roads compared with its
European neighbours, the number of child casualties is proportionally higher and
last year reinforced the trend, with child casualties going up by 6 per cent to 45,239.
The number of child pedestrians killed on the road went up from 135 to 173, a rise
of 28 per cent.
The increase in injuries means that the Government has virtually no chance of
meeting its target of reducing total roads casualties by one-third between the early
Eighties and 2000. However, it will easily achieve the target on deaths if present
trends continue.
Edmund King, campaigns manager of the RAC, said: ‘There are very worrying
features about these figures, particularly on child deaths. One thing that could be
done quite easily is to bring the clocks into line with the Continent so that children
would not have to go home from school in the dark.’
He says that the increase in serious injuries shows that the number of accidents is
rising and he feels many are caused by drivers feeling too insulated in their modern
cars. Mr King said; ‘They listen to the stereo, have the heater on and it’s almost as if
the outside world doesn’t exist. And then they fall asleep or make a mistake . . .’
Brigitte Chaudhry, national secretary of RoadPeace, an organisation for road accident
victims, said the figures on deaths may be misleading; ‘Deaths are only counted
as such if they occur within 30 days of the accident. Nowadays, many people are
kept alive for much longer thanks to modern medical techniques and die later than
that.’
She added that the main reason for the reduction in deaths over the last 30 years is a
decline in the number of vulnerable road users, such as pedestrians and cyclists,
using the roads: ‘As there are fewer pedestrians on the road and more are getting
hurt, it suggests that roads are more dangerous and not safer.’
3 Health check
It is not often that the heads of our prestigious medical colleges bandy about words
such as ‘terrifying’ and ‘time bomb’, but last week three of them came together in an
unprecedented move to issue a warning about the soaring numbers of overweight
and obese people in Britain. Two thirds of men and women are now classed as
overweight or obese. One in 10 children under four is obese, rising to one in six in
the five–15 age group. Obesity has doubled among children, trebled among women,
and nearly quadrupled among men over the last 20 years. . . .
In the same way that many people claim that their weight ‘just crept up over the
years’, so, too, has the experts’ realisation of the full extent of the obesity problem.
Everyone – the doctors, the food industry, the Government and the obese – agrees
that the causes are complex and the solutions multi-factorial. It is not just about fat,
greedy people eating more than they need to and being too lazy to do something
about it. But a trip to the Bluewater [shopping centre] is a neat example of a lot of
the causes – and solutions.
The rise of these huge, out-of-town shopping centres has only added to the culture
of the car. Bluewater is not within walking distance of anywhere – everyone drives
to it. When they do get there, there are lifts from the car parks to the shops.
Escalators take you from one level to another. The distance that anyone has to move
under their own steam is minimal.
An interesting factor in the whole debate about obesity is that the average person
actually eats fewer calories and less fat per day than 30 years ago – but does far less
exercise. Parents drive their children 500 yards down the road to school, and then
carry on to their place of work. People drive to the park to walk their dog, or to the
newsagents to get a newspaper.
Children in particular suffer from this. They no longer cycle to the shops to get
sweets, or run down the road – they are driven there. The loss of playing fields,
combined with a (perhaps irrational) public perception that paedophiles and
murderers lurk at every corner, means that many youngsters don’t even know
how to ride a bike, let alone have the freedom to get on one and burn some
energy.
But back to Bluewater. A glance around the food court highlights another problem
– portion sizes. Order a McDonald’s burger, and the first thing you will be asked is
whether you want to ‘go large’. Bags of crisps come in maxi-sizes, chicken meals in
‘bargain buckets’.
(Extract from ‘Health Check’ by Maxine Frith, The Independent,
Monday, 16 February 2004)

Offering alternative explanations

For each of the following passages, identify which part of the passage is the explanation,
and which part is the fact which is being explained. Then suggest an alternative
explanation for this fact. Do not worry if you are uncertain whether your explanation is
true. Just try to think of something which, if it were true, would be another possible
explanation:
1 Public confidence in the police force is declining at the same time as fear of crime is
growing. People’s lack of confidence in the police is the reason why they are so much
more fearful of crime.
2 Why has the divorce rate increased so much over the last thirty years? It is because
there are so many more couples these days who are unhappily married.
3 The human race has never received a well-authenticated communication from beings
elsewhere in the universe. This is because the only intelligent life in the universe is on
our own planet.
4 The number of cars per head of population in Britain continues to rise. This is
why, whenever a new road such as the M25 is built, the density of traffic in that area
increases.
5 Because the weather was so bad in Britain last summer, the number of people taking
holidays in British resorts declined.
6 A report by a Select Committee of MPs says that parents’ failure to discipline
their children is to blame for some young people’s disrespect for others, their casual
attitude to violence, and their involvement in bullying at school.
7 Greece has a much lower incidence of smoking-related deaths than the UK, even
though Greece also has a much higher percentage of smokers. This is due to differences
in smokers’ habits. Where cigarettes are very expensive, as in the UK, people
smoke the cigarette right down to the tip, whereas where cigarettes are cheaper, half
of the cigarette is thrown away.
8 Many surveys have reported that the Danish are the happiest people on earth. Of
course they are, because they have very low expectations, and thus are pleasantly
surprised when something good happens.
Summary: Evaluating explanations
1 Identify any assumptions underlying the explanation.
2 Think of any possible alternative explanations.
3 Try to think of further evidence that could rule out some of the possible
explanations.
4 If you still think that there is more than one plausible explanation, reserve
judgement on the question until further evidence emerges.

QUESTIONING EXPLANATIONS

Some pieces of reasoning, rather than trying to convince us that we should accept a
particular conclusion, aim instead to explain something which we already accept as being
true. This is a case of giving reasons why something is as it is, rather than giving reasons
for believing something. The difference is illustrated by the following report from The
Independent of 17 February 1994.
Latest figures for cancers in England and Wales show an increase of 4 per cent in
1988. Richard Doll, consultant to the Imperial Cancer Research Fund, said one
explanation was the rising number of elderly people.
Richard Doll’s comments are not trying to convince us of the fact that cancers increased in
1988. They are taking the truth of that for granted, and trying to explain why this increase
occurred.
This is a case of an explanation occurring as an independent piece of reasoning, but we may
also find explanations offered within an argument, as part of a longer passage of reasoning.
What we need to know about an explanation is whether it is the correct explanation. It
may not be easy to settle such a question, but there are strategies we can use to attempt to
make some assessment of an explanation. One is to examine any questionable assumptions
underlying the explanation. Another is to think of possible alternative explanations, and
try to find further evidence which may rule out some of these explanations. If we can
think of two or three equally plausible explanations of something, then we should be
cautious about accepting any of them as the correct explanation until we have further
information.
We can try these strategies on the above example, although it may seem presumptuous to
question the judgement of a leading authority in cancer research! What assumptions
underlie Richard Doll’s explanation? If the increase in cancers is attributable to ‘rising
numbers of elderly people’, this must be because people who, had they lived in earlier
times, would have died from other diseases (which are now more easily treatable or
preventable) are living to an age at which they are likely to get cancer. No doubt further
support for this assumption could be found by examining figures on the incidence of
cancer in different age groups.
What alternative explanations of the increase in cancer can we suggest? Well, there would
be an increase in cancer figures if the population in general were more susceptible to the
disease – perhaps because of pollutants in the environment. There would be an increase in
the figures if particular groups had a greater incidence of cancer, due to changes in habits
and practices. For example, it could be that new medications for circulatory diseases cause
more cancers, or that more cancers are caused by more women taking hormone replacement
therapy. Light could be shed on the plausibility of these alternative explanations
by examining figures on the incidence of cancer amongst different groups. We are not
suggesting that Richard Doll’s explanation is likely to be incorrect – in fact he is more
than likely to have taken all these factors into account before offering his explanation.
Possibly he meant that part of the increase in the incidence of cancer could be explained by
greater longevity. But the example serves to illustrate the way in which we can question
explanations, perhaps reserve judgement on them until we have more information, and
perhaps take steps to investigate which of various alternative explanations is the most
plausible.
The following passage describes a piece of research which aimed to find out the most
plausible explanation of a known fact. It is adapted from an article in The Independent on
Sunday, 25 June 1995.
Motorists in their teens and twenties have a low opinion of elderly drivers, whom
they regard as bumbling old fools who shouldn’t be allowed on the roads.
Some old drivers are indeed incompetent, and data from the US has shown that the
accident rate for drivers rises substantially after the age of 70. [A research team at
the University of California in Los Angeles has now carried out a detailed study of
the abilities of elderly drivers.]
The research team recruited volunteers in their early seventies who, according to
their doctors, had signs of early dementia due to Alzheimer’s disease, or to narrowing
of the arteries. Other drivers of the same age had diabetes as their only medical
condition, and a group of younger drivers was used for comparison.
All the drivers – the demented, the diabetics and the young controls – were taken
on a drive around a three-mile road network with intersections, speed bumps, traffic
signs, signals and parking lots. Each driver’s performance was graded by an
instructor in the car, which was fitted with an on-board computer which recorded
braking speed, steering, crossing the centre line, and so on. The drivers also worked
their way through a series of standard tests of mental ability, concentration and
short-term memory.
The results showed that the 70-year-olds with diabetes did just as well on the test
drives and mental tests as the younger drivers. The drivers with early dementia did
worse. They drove slowly, and the mistakes they made were serious – for example,
turning into a one-way street marked ‘no entry’.
The conclusion was that drivers in their 70s in normal health (with normal vision)
can perform at a level comparable with young, healthy adults – at least in a suburban,
non-stressing environment. Statistics showing that drivers in this age group
have high accident rates are, the report says, at least partly attributable to people
continuing to drive after they have become mildly demented.
(‘Second opinion’, Dr Tony Smith, The Independent on Sunday, 25 June 1995)
Before reading on, ask yourself the following questions:
• What was the known fact which the study sought to explain?
• What explanation would the author expect young motorists to give?
• What explanation does the report of the study give?
The passage tells us in the second paragraph that data from the US shows that the accident
rate for drivers rises substantially after the age of 70. This is the fact which is to be
explained, and it means, of course, that as a group the drivers aged over 70 have a higher
percentage of accidents than those aged under 70. It is clear from the first paragraph that
the author would expect young drivers to explain this fact by saying that all drivers aged
over 70 are incompetent, and therefore more likely to have accidents. The study did tests
to assess the competence of drivers, and found that those aged over 70 who had dementia
were less competent than young drivers, but those aged over 70 who did not have this
medical condition were no less competent than young drivers.
This suggests that the most plausible explanation of the higher accident rate amongst
drivers aged over 70 is that some drivers aged over 70 are incompetent due to dementia.
We should note that the article suggests that the driving test was conducted in a ‘suburban,
non-stressing environment’. If this is correct, then, in order to be certain that the
explanation offered by the study was the most plausible, we would want some evidence
about the competence of both young drivers and drivers aged over 70 in more stressful
traffic conditions.
The report does not make clear the age range of the ‘young control’ group. Dividing all
drivers into only two groups, over 70 and under 70, obscures any statistical differences in
the very large under-70 group. This is an example of how critical of statistics we must be,
even when we accept them. For example, drivers aged under 25 have a significantly higher
accident rate than those over 25. Elderly drivers might wish to argue that this showed a
high incidence of undiagnosed dementia among younger drivers!

EVALUATING FURTHER EVIDENCE Exercises' Answers

include engineering, then (a) adds nothing to the information in the passage
that enrolment in engineering courses has increased.
(b) does not weaken the argument. It simply emphasises the problem – the
need to attract more engineers into teaching – to which the argument offers a
solution.
(c) has no impact on the argument. The high salaries paid by businesses to
those with advanced engineering degrees are likely to tempt these people away
from teaching. This makes no difference to the recommendation to solve the
problem of the shortage of engineering teachers by reducing salaries for those
without advanced degrees.
(e) has no impact on the argument. The argument is about a way of increasing
the incentive for engineering graduates to pursue postgraduate studies. The
funding of research programmes would not increase this incentive, unless it
made generous awards to potential students. (e) makes no claim that businesses
fund generous awards to students.
3 The answer is (e).
(e) strengthens Joan’s claim by providing evidence that some heroin addicts are
likely to commit serious crimes in order to get supplies of the drug. This
supports the claim that the amount of serious crime may be reduced if heroin
addicts were given free supplies of the drug.
(a) does not strengthen Joan’s claim, it weakens it. If heroin addicts were more
likely to be violent when under the influence of heroin, they might commit
crimes at such times. Providing them with free heroin would not reduce the
amount of crime, if any, committed by heroin addicts.
(b) does not strengthen Joan’s claim, because she is not trying to show that
supplying heroin to addicts would make economic sense. She is claiming simply
that it would reduce crime.
(c) does not strengthen Joan’s claim, for the same reason that (b) does not
strengthen it.
(d) does not strengthen Joan’s claim because it concerns crime which is not
related to the use of heroin. This tells us nothing about the effectiveness of
Joan’s proposed method of reducing drug-related crime.
4 The answer is (a).
If (a) is true, then there is a good reason for the automobile association to
continue testing direction indicators, since if they do not, the numbers of
defective direction indicators may increase. Hence (a) weakens the case for
stopping inspection of direction indicators.
(b) on its own does not weaken the argument. It seems to offer a reason for
making sure that direction indicators are in good working order. But this
does not weaken the recommendation to stop inspecting them, unless (as (a)
suggests) stopping the inspections would result in more faulty indicators.
(c) does not weaken the recommendation, unless there is reason to believe that
the inspection procedures need to be as thorough as those in neighbouring
states. (c) does not provide such a reason.
(d) does not weaken the recommendation to stop testing direction indicators.
It appears to be offering a reason in support of the recommendation, but in
fact it makes no difference either way. Even if automobiles fail the inspection
on the grounds of other safety defects, there may still be automobiles with
defective indicators on the roads.
(e) does not weaken the argument, although it may look as if it is offering a
reason for retaining inspection of indicators. Inspecting them would not bring to
light other defects not covered by the safety inspection system. So (e) is irrelevant
to the question as to whether direction indicators should be inspected.
5 The answer is (d).
The researchers concluded that if parents monitored (presumably meaning
‘controlled’) the amount of time which their children spent watching
television, the children’s performance in school would benefit. So the
researchers were assuming that the relationship they found between the hours
the children spent watching television and their level of performance in school
was evidence that watching for longer periods caused poorer performance. The
researchers had discovered a correlation, but a correlation between two things
does not necessarily mean that one thing causes the other. (See the discussion
on p.45.) (d) strengthens the idea that there is a causal connection. If differences
in performance are less when hours watching television are roughly
the same for all children, then it is likely that differences in time spent
watching television causes differences in performance.
(a) gives more detail about the figures upon which the claim in the first sentence
is based, so it strengthens the statement that if children watched between
two and three hours of television per day, they were likely to perform less well
in school. This is stronger evidence that there is a correlation, but gives no extra
evidence of a causal connection. So it does not strengthen the conclusion,
which relies on the assumption that there is a causal connection. Provided we
assume that there is a causal connection between amount of television viewing
and school performance, (b) could be regarded as giving an additional reason
why school performance might improve if parents monitored their children’s
television viewing. But since (b) does nothing to strengthen the idea that there
is a causal connection, it does not strengthen the conclusion of the researchers.
(c) does not strengthen the idea that watching television for two or more hours
per day causes poorer performance in school. Instead it introduces a new factor
– the amount of time spent reading – which may have an effect on school
performance.
(e) does not strengthen the idea of a causal connection, because although
it suggests that some children replaced their television watching with
reading, it does not comment upon how this affected their performance in
school.
6 The answer is (a).
(a) weakens the argument by showing that even if ex-prisoners do not pursue
the occupation for which they have prepared whilst in prison, the skills they
have learnt during training in prison may nevertheless be of use in whatever
occupation they take up.
(b) provides an objection to scrapping career training programmes in prison. But
this is not the same as weakening the argument, because it has no impact on
the claim that it is unwise to continue such programmes since they do not
achieve their aims.
(c) mentions an advantage of prison career training programmes, thereby to
some extent weakening the claim that it is unwise to continue them. But this
does not weaken the argument as much as (a), which shows that the claim
upon which the conclusion of the argument is based – that the programmes do
not achieve their aim (which we can assume is to provide skills which will be
useful in future employment) – is not true.
(d) does not weaken the argument, because it simply emphasises that training
programmes have the goal which the argument claims they do not achieve. (d)
tells us nothing about whether they achieve that goal, hence has no impact on
the conclusion that these programmes should be scrapped.
(e) does not weaken the argument, because the argument relies on the claim
that prisoners choose not to pursue the occupation for which they have trained
whilst in prison. This does not imply that they have no choice whilst in prison,
nor does (e) imply that they will not change their choice of occupation after
leaving prison.
7 The answer is (e).
(e) weakens the argument by providing evidence that the physiological changes
recorded by a lie detector may result from stress other than the stress caused
by lying. This suggests that, contrary to what the conclusion claims, reliable lie
detection is not possible.
(a) has no impact on the argument, because reliable lie detection may be
possible, even if the machines are expensive and require careful maintenance.
(b) suggests that for some people who are lying, lie detectors will indicate
symptoms of only moderate stress. But this does not weaken the claim that
reliable lie detection is possible.
(c) does not weaken the argument, because it does not suggest that it is impossible
to find and train the personnel who can use lie detection instruments
effectively.
(d) does not weaken the argument, because reliable lie detection may be possible
even if some people misuse or abuse lie detecting equipment.
8 The answer is (c).
The conclusion of the argument is that it is unrealistic to expect flu vaccines to
give total protection against the virus. The reasons given for this are that the
prediction as to which flu strains will be circulating is made a long time before
the vaccine is used, and that if a new strain of flu appears the vaccine will not
be protective against it. (c) strengthens the argument by providing another
reason why total protection cannot be guaranteed, since if the vaccine works
less well in those people who are most at risk, it can be expected that some
people will not be protected by the vaccinations.
(a) is irrelevant to the argument, because the conclusion refers specifically to
protection against the flu virus, and there is no information in the passage as to
connections between the flu virus and colds.
(b) suggests that it may be wise to vaccinate children against flu, in order to
reduce the spread of the virus, but is not relevant to the claim that we cannot
expect total protection from vaccinations.
(d) does not strengthen the argument because it gives a reason for accepting
that the flu vaccination is extremely effective, and gives no reason as to why it
is unrealistic to expect it to be effective in all cases.
(e) is not relevant to the argument as to the effectiveness of the flu vaccine,
since it concerns only those who have not been vaccinated.
9 The answer is (d).
The argument concludes that allowing drivers to use the hard shoulder on
motorways at peak times is preferable to other possible measures, on the
grounds that it solves the problem of congestion on motorways relatively easily
and cheaply, as evidenced by the success of a recent trial of the scheme. However,
if (d) is true, then the increase of traffic may mean that the scheme does
not solve the problem of congestion on motorways, despite the fact that the
trial run was successful, and this may mean that other schemes would provide
more effective solutions.
(a) is irrelevant to the claim that using hard shoulders would solve the problem
of congestion. It simply suggests that it is possible to have motorways without
hard shoulders, but has no implications as to how this would affect traffic flow.
(b) does not weaken the argument, since although it suggests that many people
are not discouraged from using motorways by the availability of public transport,
it gives no definite information as to future increases in the volume of
motorway traffic.
(c) gives a reason for thinking that the measures that the argument rejects
could be difficult to implement, hence it does not weaken the argument.
(e) mentions something that could be seen as a disadvantage of using the hard
shoulder (i.e. that the speed limit will be lower), but this does not weaken the
argument because it does not show that the proposed scheme would not
reduce congestion, nor that it would not be preferable to more expensive
measures.
10 The answer is (e).
The argument gives two reasons for disapproving of carbon offsetting schemes;
first, that the availability of the scheme makes people think there is nothing
wrong with flying, and second that customers cannot know that their financial
contribution does reduce carbon emissions. (e) strengthens the case against
carbon offsetting by showing that in some cases any reduction in carbon
emissions would have happened anyway, thus cannot be claimed to compensate
for the carbon emissions caused by someone taking a flight.
(a) gives a reason for thinking that the business of carbon offsetting may
eventually be better regulated, and thus that some of the objections in
the argument may eventually not apply. Hence it does not strengthen the
argument.
(b) does not strengthen the argument, since it suggests that the carbon emissions
produced by aircraft may be less problematic than the argument assumes.
(c) neither strengthens nor weakens the argument. It suggests that it is worthwhile
to make financial contributions to energy saving schemes, but has no
implications for the question as to whether this should be done by carbon
offsetting schemes.
(d) is irrelevant, since it merely suggests other ways of reducing carbon emissions,
and has no implications as to the desirability of carbon offsetting schemes.

Exercises:

EVALUATING FURTHER EVIDENCE Exercises

Often when we present a case to someone else for accepting a particular conclusion, they
will say, ‘Ah, but what about . . .?’, offering some piece of information which we have not
mentioned and which they think weakens our case. In relation to our earlier example
concerning the dangers of smoking, imagine someone saying to you, ‘Knowing that smoking
is dangerous cannot be sufficient to stop people from smoking, because there has been
so much publicity about the health risks, and yet people still smoke’. Let us suppose that a
survey of smokers’ beliefs has been carried out. You might then reply to the above statement,
‘Ah, but what about that survey which showed that, unlike non-smokers, smokers
generally believe that smoking is not bad for one’s health?’ The other person must then
consider what impact this has on their conclusion.
Being able to assess the impact of additional evidence is valuable because people frequently
challenge each other’s reasoning by offering some new piece of information. One response
to such challenges would be to question the truth of the new piece of evidence, and this
would involve one of the skills we have already mentioned – that of evaluating the truth of
evidence or reasons. Another response might be to say that even if the new piece of
evidence were true, it would not weaken the conclusion. This involves the other vital skill
which we have discussed – that of assessing the degree of support which a reason gives to a
conclusion.
Of course, the context may not be one in which we are trying to defend a conclusion – nor
should we be thinking in terms of the necessity to defend a conclusion at all costs. That
would be to indulge in uncritical thinking – being determined to believe something even
in the face of evidence to the contrary. So we must be prepared to acknowledge that
sometimes additional evidence will weaken our conclusions. Sometimes new evidence
comes to light not in the context of a discussion, not when someone else is trying to
undermine one’s own reasoning, but simply in relation to a subject upon which we already
hold an opinion, and believe that we hold that opinion for good reasons. Once we see that
the new evidence is relevant to the issue, we must then consider whether it counts for or
against our earlier opinion – that is to say we must consider whether it strengthens our
reasoning and not merely whether it weakens it.
This exercise gives you practice in evaluating the impact of additional evidence on an
argument. For each of the following multiple choice questions, pick the correct response,
explain why it is the correct response, and explain why each of the other responses is
incorrect.
1 A recent study found that school-age children who participate in school-related
sports activities fight less during school and school-related activities than do those
children who do not participate. It was concluded that sports must satisfy an aggressive
impulse which would otherwise be released through fighting.
Which of the following, if true, weakens the conclusion referred to in the above
passage?
(a) School-related sports activities are always supervised by adults.
(b) Supervisors of school-related sports activities discourage participants from being
extremely aggressive.
(c) Children who participate in school-related sports activities tend to be more
aggressive physically than those who do not participate.
(d) Approximately 85 per cent of the fights children get into during school or
school-related activities take place during break times.
(e) Most schools suspend those who fight during school or school-related activities
from the schools’ sports teams.
(Law School Admission Test, 1982)
2 Although the number of undergraduates studying engineering has grown greatly
over the last five years, there may be a shortage of engineering teachers in the near
future because the number of people receiving PhDs in engineering, those most likely
to teach, has not been increasing. This results because the high salaries offered to
engineers without advanced degrees reduce the incentive to pursue post-graduate
studies. Therefore, businesses will have to recognise that their long-term interests
would best be served by reducing salaries for those without advanced degrees.
Which of the following, if true, would most weaken the above argument?
(a) Enrolment in the sciences has grown over the last five years.
(b) Fewer than half of the people who have received PhDs in engineering teach
full-time.
(c) Businesses pay high salaries to engineers with advanced degrees.
(d) The increases in engineering enrolment are due to the high salaries paid by
businesses.
(e) Many university programmes are funded by businesses interested in engineering
research.
(Law School Admission Test, December 1983)
3 Joan: One method of reducing serious crime in the United States is to adopt the
English system of providing free heroin to heroin addicts.
Anna: That’s absurd. It’s just like giving free cars to automobile thieves.
Which of the following, if true, would most strengthen Joan’s argument?
(a) Heroin addicts are more likely to be violent under the influence of drugs than
when they are anticipating using those drugs.
(b) The amount of money needed annually to supply heroin to heroin addicts is less
than the amount lost annually by the victims of drug-related crimes.
(c) It is cheaper to provide addicts with drugs than to jail them after they have
committed crimes.
(d) The amount of serious crime committed by non-addicts is roughly equal in
England and the US.
(e) A substantial amount of serious crime is committed by heroin addicts in order
to support their habits.
4 Since only 4 per cent of all automobiles fail the state’s annual safety inspection
solely because of defective direction indicators, the state’s automobile association
recommends that direction indicators no longer be inspected. Although they are an
important safety feature, too few are defective to make the expense of testing them
worthwhile.
Which of the following, if true, points out the most serious weakness in the
recommendations of the automobile association?
(a) Owners will no longer maintain their automobile direction indicators in
working order if the inspection requirement is dropped.
(b) Owners of automobiles with defective direction indicators may not have
learned to use manual direction signals.
(c) Eliminating the inspection of the direction indicators will make the state’s
inspection procedure less thorough than those of neighbouring states.
(d) Automobiles with defective direction indicators will fail inspection anyway if
they have other safety defects.
(e) Automobiles that have defective direction indicators may have other defects not
covered by the safety inspection system.
(Law School Admission Test, February 1983)
5 A recent study found that if children watched up to one hour of television a day,
their performance in school was unaffected, but if they watched between two and
three hours a day, they were likely to perform considerably less well than their peers
who watched less. The researchers concluded that if parents carefully monitored the
time their children watched television, the children’s school performance would be
maintained at adequate levels.
If true, which of the following statements about the children in the study would
most strengthen the conclusions of the researchers?
(a) Most of the children who performed at below-average levels in school watched
more than two hours of television a day.
(b) Children who watched television mostly at weekends performed better in
school than children who watched television mostly on school nights.
(c) Children who spent more time reading than watching television performed
better in school than those who did not.
(d) The disparities among the children in terms of school performance lessened
when the television viewing habits of the children became more uniform.
(e) The children who reduced the amount of television they watched daily spent
the extra time reading.