Critical Thinking Skills - Developing Effective Analysis and Argument(2)

Answers to activities in Chapter 7 (continued)
opponent so the comparison is an effective one
in arguing that the new party has a chance of
success. The validity of the comparison would
be demonstrated at the elections if the smaller
party did better than the bigger parties.
Passage 7.72
This compares the premises of an argument to
the foundations of a building. This comparison
is valid as both provide an underlying structure
for what is added later. In both cases, if the
basis is not solid, later additions may be
unstable.
Passage 7.13
This compares emotions to a pressure cooker.
This comparison is made in order to argue that
emotions cannot be controlled. However, the
comparison isn't valid as it isn't comparing like
with like: human emotions are not like steam
under pressure, The underlying argument is
based on false premises: that emotions cannot
be controlled and that pressure cookers
inevitably explode at boiling point. However,
there are methods for managing emotions. An
explosion isn't inevitable, either, when the
contents of a pressure cooker reach boiling
point, as there are control mechanisms to let out
the steam. The comparison does not help us to
understand why the defendant couldn't control
his emotions.
Passage 7.74
This compares failures in the stock market to
health and safety matters for the human body.
The passage is based on the assumption that it is
reasonable to expect compensation for accidents
and ill-health, but, in reality, that varies
depending on circumstances such as the country
and insurance polices. The author is attempting
to make the argument for financial
compensation seem more plausible by
comparing financial loss to other major events
for which compensation seems reasonable. The
comparison is not valid because:
Ill-health and accidents do not automatically
bring compensation
Even if compensation for major health issues
was automatic, the comparison still would
not be valid. Health and finance are not
comparable in terms of the kinds of choices
people have, their control over the risks, and
the advance action they can take to avert the
consequences.
Answers: Necessary and sufficient conditions (p. 11 1)
Proposition Necessary Sufficient
Ex. Example: Birds have wings.
The item has wings.
Therefore it is a bird.
Yes. Wings are a
necessary condition
for the item being
a bird
1 The report makes reference No. It is not a
to branches. It must be about necessary condition:
a tree.
a report could be
about a tree without
referring to branches.
No. The reasons given to support the argument that
the item is a bird are not sufficient to satisfy the
definition of a bird. This would include 'usually flies', is
animate, lays eggs, has two legs, has feathers. The
information given is not sufficient to rule out an
aeroplane or a toy.
No. The reasons given to support the argument that
the report is about a tree are not sufficient to prove
the case. The report could be referring to branches
of an organisation such as a bank.
O Stella Cottrell (2005), Critical T/ziilkiilg Skills, Does it add up 123
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