Practice with Analysis
The following examples are from Anne Thomson's Critical
Reasoning. Each of the passages contains weak reasoning.
After identifying the argument, consider what alternative explanations
or reasons might also be possible. Only click on answer after
struggling with the question for a good period of time.
1. Men are generally better than women at what psychologists
call 'target directed motor skills', but what the rest of us
call 'playing darts.' Many people would say that this is not
due to innate biological differences in the brain, but is due
to the fact that upbringing gives boys more opportunities to
practise these skills. But there must be some innate difference,
because even three-year-old boys are better than girls of the
same age at target skills.
2. Allowing parents to choose the sex
of their children could have serious social costs. There would
be a higher percentage of males who were unable to find a female
partner. Also, since it is true that 90 per cent of violent
crimes are committed by men, the number of violent crimes would
3. When people live in a house for a
long period of time, they develop a strong commitment to the
local neighbourhood. So the continued fall in house prices may
have a beneficial effect. The middle classes will become enthusiast
campaigners for better schools, and against vandalism, traffic
congestion and noisy neighbors.
4. If the money has been stolen, someone
must have disabled the alarm system, because the alarm easily
wakes me if it goes off. So the culprit must be a member of
the security firm which installed the alarm.
5. The campaign to eradicate measles
has been so successful that many doctors have never seen an
actual case. Ironically, this puts those few people who do contract
the disease in greater danger than they would have been before.
The disease can cause serious complications, and it is difficult
to diagnose without previous experience because the symptoms
are similar to those of several other diseases.
6. There is a much higher incidence of
heart attack and death from heart disease among heavy cigarette
smokers than among people who do not smoke. It has been thought
that nicotine was responsible for the development of atherosclerotic
disease in smokers. It now seems that the real culprit is carbon
monoxide. In experiments, animals exposed to carbon monoxide
for several months show changes in the arterial walls that are
indistinguishable from atherosclerosis.
7. Patients on the point of death, who
either died shortly afterwards or were revived, have often reported
visions of places of exquisite beauty, intense feelings of peace
and joy, and encounters with loved ones who had predeceased
them. These experiences clearly suggest that there is life after
death. Skeptics often claim that such phenomena resemble certain
altered states of consciousness that can be induced by drugs
or organic brain disease. This objection fails, however, because
most of the patients whose experiences of this nature have been
reported were neither drugged nor suffering from brain disease.
8. The growth in the urban population
of the USA has put increasing pressure on farmers to produce
more food. Farmers have responded by adopting labour-saving
technology that has resulted in a further displacement of population
to cities. As a result, the farm population, formerly a dominant
pressure group in national politics, has lost political power.
9. Human being shave the power either
to preserve or to destroy wild plant species. Most of the wonder
drugs of the past fifty years have come from wild plants. If
those plants had not existed, medicine could not have progressed
as it has, and many human lives would have been lost. It is
therefore important for the future of medicine that we should
preserve wild plant species.
10. Thirty years ago the numbers of British
people taking holidays in foreign countries were very small
compared with the large numbers of them traveling abroad for
the holidays now. Foreign travel is, and always has been, expensive.
So British people must on average have more money to spend now
than they did thirty years ago.