Thinking Skills: Critical Thinking and Problem Solving

2.10 Flaws and fallacies 71

Not studying may have worked for Beth, just

as ignoring advice worked for Amulk, but that

doesn’t mean it will work for anyone else – let

alone everyone.

Generalising from the particular

It is easy enough to see that [1] and [2] contain

a serious flaw in the reasoning, one that makes

the conclusion unreliable. It is also easy to see

that it is the same kind of flaw in each case,

even though the contexts are different. But

what exactly is the flaw? How do we identify it?

[1] and [2] are both examples of a very

common flaw. It is known as generalising from

the particular. We call something a particular if

it is just one instance, or one of a limited

number of instances. The particular in [1] is the

success of one company. In [2] it is a single

person’s exam results. Neither of these is a

strong enough reason to support a sweeping

generalisation. (See also Chapter 2.2.)

Arguing from anecdotal evidence

Another way in which you could describe the

flaw in both of these arguments is to say that

they rely on anecdotal evidence. An anecdote

is a story, usually just one among many, often

different, stories. So a piece of anecdotal

evidence is a kind of particular; and arguing

from anecdotal evidence can be a reasoning

error if the conclusion is an unwarranted

generalisation.

However, anecdotal evidence can support

some conclusions. Look, for example, at this

next argument:

[3] Three people fell through the ice last

winter when they were walking across the

lake. Seriously, you should think twice

before you try to cross it.

If the anecdote – the first sentence – is true,

then it is a sound argument, and its

conclusion is sound advice. There is nothing

wrong with the evidence in [3], even though

it is still purely anecdotal. The fact of three

The conclusion is the second sentence. The
first, longer sentence is the reasoning given
in support of it. On inspection we can see
that this long sentence really contains three
claims rolled into one. So a full analysis of it
would be:

R1 Amulk’s company is/was an outstanding

success.

R2 It was launched against the advice of

bankers . . . etc.

IC One person’s vision can prove all the

experts in the world wrong.

C Anyone thinking of setting up in business

should trust their own judgement, and not

be influenced by the advice of others.

We don’t know whether or not the two initial
reasons, R1 and R2, are true, but we’ll assume
that they are. There is no reason to believe
they are untrue. If they are true then it does
seem that IC is also true; for if Amulk’s
company really was such a success, and the
bankers and others all advised against it, then
it seems fair to say one man’s success
(Amulk’s) can prove the experts wrong. It
means assuming that the bankers and others
are ‘experts’, but we can let that pass. So we
can accept that the first stage of the argument
is sound.
The big question is whether the main
conclusion follows from the intermediate one
(IC). This time the answer is ‘No’. Even if
everything we are told is true, we cannot
conclude from this one single example of
success, or from this one misjudgement by the
‘experts’, that anyone setting up in business
should ignore expert advice. It would be a
crazy conclusion to draw, a reckless thing to
do. It would be like arguing as follows:

[2] Beth passed all her exams without doing

any work. So anyone taking an exam

should stop studying!