Thinking Skills: Critical Thinking and Problem Solving

74 Unit 2 Critical thinking: the basics

and not permitted to reopen until it has

been given a certificate of fitness from

hygiene inspectors. Today the Bayside is

closed.

Can any of the following claims safely or

reliably be inferred from the passage above?

A The source of the outbreak of food

poisoning was the Bayside fish

restaurant.

B Fish was the cause of the outbreak.

C The Bayside has been closed down by

the inspectors.

Activity

Commentary

According to the passage we have three facts:

•   Four people who reported sick had

recently eaten at the Bayside.

•   Any establishment responsible for food-

related sickness is closed by the authorities.

•   The Bayside is closed (today).

So, between them, do they justify any of the

three claims? We’ll take the claims in order,

starting with A. Although there is a suspected

link between the restaurant and the people

reporting symptoms, it cannot be inferred

that the restaurant was responsible for the

outbreak. If still in doubt, read [6] again.

Note, for example, that we are told nothing

about the four people other than that they

ate at the Bayside and then reported sick. It is

possible that there were other connections

between them: that they were all friends or

family and had shared other food and drink

besides the meal at the restaurant. Nor are we

told if there were others who were sick

besides the four who were mentioned in the

report. There may have been others who did

not report their illness. If there were others,

we do not know whether they had eaten at

same as showing up its internal flaws. Even if

we accept that B is true, you could still argue

that Amulk’s experience proved them wrong

on this occasion. The flaw is not that Amulk

knew less than the experts, because nowhere in

the argument is it claimed that he knew

anything at all – only that he was successful.

The mistake is in drawing a conclusion about

other people’s chances of success from Amulk’s

success alone. So B does not point to the flaw.

That leaves C. C effectively raises a doubt

about the conclusion by suggesting that the

real explanation for Amulk’s success may

simply have been that he was lucky on this

one occasion. That way it would still be better

as a general rule to heed expert advice,

contrary to the conclusion of the argument.

Alternatively, in Amulk’s case, the particular

individuals who advised him may not have

been the best. Again, that does not mean that

going against advice is more likely to succeed

than following it. By identifying other

equally likely explanations for Amulk’s

success, C exposes a serious flaw in the

reasoning.

Drawing inferences

To infer something means to draw it as a

conclusion, usually from some evidence or

information. A sound or ‘safe’ inference is

one that is adequately supported by the

information. Otherwise it is unsafe. (Other

words you could use are ‘unreliable’,

‘unjustified’ or ‘unwarranted’, all of which

can be applied to claims generally.)

Consider the following report in a local

newspaper:

[6] Doctors investigating an outbreak of

suspected food poisoning discovered

that four of the people who had reported

sick had eaten at the Bayside fish

restaurant the day before; and all had

eaten fish. Any establishment that is

found to be responsible for food-related

sickness will be closed by the authorities