Ways in which arguments can be flawed

We have now seen five different ways in which an argument can be flawed. In Example 1,
on the effects of television violence, one interpretation of the argument was flawed
because it drew a general conclusion about the effects of television from just one case (advertising)
of which the effects were claimed to be known. The flaw in the other interpretation
of the argument was that it relied on an inappropriate analogy or comparison. In Example 2,
the original argument about increased affluence and health, the argument was flawed
because it drew its conclusion on the basis of insufficient evidence (the evidence that some old
diseases are more prevalent), whilst at the same time failing to look for other relevant
evidence (for example, the reduced incidence of some diseases, the percentage of people’s
lives during which they are free of illness, and so on). In Example 3, claiming that
increased affluence had produced an improvement in the health of the population, the
argument was flawed because it assumed that because two things have occurred together, one
has caused the other, and because it failed to consider other possible causes of the improvements
in the health of the population. In Example 4 the argument concluded that
exhaustion of the mineral resources of the world was not imminent. It was flawed because
it disregarded relevant factors (the finite nature of mineral resources, and the rate of use of
mineral resources).
There are some flaws which appear quite often in reasoning, and which can deceive the
reader into thinking that good reasoning has been presented. This is true of the flaw
in Example 1 above – drawing a general conclusion from just one example – and of
the flaw in Example 3 – assuming a causal connection on the basis of an association
between two things. These are two instances of faults which are generally called ‘fallacies’,
and some texts begin their discussion of faults in reasoning with a list of fallacies. In this
text we have started with a different approach, which requires engaging with the particular
subject matter of each argument. The skill which needs to be developed is an ability to
say what is going wrong in the move from the reasons to the conclusion in a particular
argument.
There are two reasons why we should not rely simply on lists of fallacies when trying to
identify flaws. The first is that arguments can be flawed in ways which do not appear in
lists of fallacies – the flaw in Example 4 above is evidence of this. Second, relying simply on
lists of fallacies can encourage us to overlook the context of the argument, and to classify
arguments in a way which can cut off further reasoning instead of allowing us to engage
with the topic in its own context.
An example can clarify our last point. A category which usually appears in lists of fallacies
is the ‘slippery-slope’ argument. This refers to reasoning in which it is claimed that a certain
action, or the introduction of a certain policy, though possibly harmless in itself, will
be the first step along a road to inevitable and undesirable consequences. For example,
someone may argue that we should not legalise the sale and use of cannabis because to do
so would set us upon a slippery slope to legalisation of more harmful drugs. A satisfactory
criticism of this argument would require more than saying: ‘this is a slippery-slope
argument, therefore it is flawed’. It would require us to say why in this particular case, the
supposed undesirable consequence need not occur. This is a much more challenging task,
because the introduction of legislation can act as a precedent in some circumstances, and
can change the climate of opinion in such a way as to make some further consequence
more likely to happen.
However, being aware of some standard fallacies may help you to see in some cases what is
going wrong in an argument, so we mention a few more here.

The ad hominem fallacy occurs when someone attempts to discredit another’s argument by
mentioning disreputable aspects of the person’s character, instead of focusing on what is
wrong with the argument itself. Establishing, for example, that someone is a bully is not a
good reason to conclude that their reasoning must be at fault. However, some personal
characteristics (for example, a tendency to exaggerate, or a temporary or permanent mental
incapacity) may be relevant to judgements about the reliability of information which others
give us. But it is fallacious to claim that a particular conclusion does not follow from
acceptable evidence or true reasons, simply on the grounds that the person drawing the
conclusion has an unpleasant personality.
One fallacious type of argument involves confusing necessary and sufficient conditions. Here
are two examples in which this occurs. See if you can state exactly what is going wrong in
each case:
You can’t win a five set tennis match if you are unfit. But you are fitter than your
opponent, so you will win.
You will be rich if you win the lottery. But you never buy a lottery ticket, so you will
never be rich.
In the first example the flaw is that it assumes that because it is necessary to be fit in order
to win a five set tennis match, being the fitter player is sufficient to guarantee a win.
But this assumption is ill-founded, because winning a tennis match depends on skill as well
as fitness. The second argument is flawed because it wrongly assumes that something
which is sufficient to guarantee riches – winning the lottery – is necessary in order to
become rich.
Someone is said to commit the straw man fallacy if their argument relies on misrepresenting
the opponent’s point of view. In January 2001, an injunction was granted preventing
publication of information as to the whereabouts of the killers of a child, James Bulger.
The judge, Dame Elizabeth Butler-Sloss, gave her reasons for the judgment – that if, after
their release from custody, the whereabouts of these two young men became public
knowledge they would be seriously at risk of death or injury, and that the European
Convention on Human Rights – now part of UK law through the Human Rights Act of
1998 – obliges the state to protect an individual’s right to life. Suppose someone objected
to the judgment on the grounds that it is based on the view that the killers should be
rewarded for becoming reformed characters during their period of detention. This would
be setting up a straw man, that is, an argument which can easily be knocked down because
it is obviously weak, but which is not what the proponent of the original argument believes
or claims.
The fallacy of begging the question involves taking for granted that which one was claiming
to conclude, as illustrated in the following argument:
We know that Jesus was the son of God, because he said so, and the son of God
would not lie.
The conclusion that Jesus was the son of God does not follow from the two reasons offered
– that he said so, and that the son of God would not lie – without the assumption that the
person who said he was the son of God was indeed the son of God, that is without taking
for granted the truth of what it aimed to prove.
We have shown some of the ways in which arguments can be flawed. In order to become
skilled in identifying flaws in arguments, it is helpful to practise on numerous arguments
on a wide range of subject matter. Using lists of fallacies may help you to begin to say what
is wrong with an argument, but remember that arguments can go wrong in ways which do
not fit neatly into these categories. We have pointed out that this was true of Example 4
above, about the world reserves of mineral resources, in which the flaw could be stated
only by referring to the particular subject matter of the argument. For the next exercise,
remember that you are to focus simply on the skill of identifying flaws – you should not
worry in this exercise about whether the reasons are true.

Summary: Identifying flaws in arguments
1 Identify the main conclusion.
2 Identify the reasons and the way in which they are meant to support the
conclusion.
3 For each step of the argument, ask ‘Does this (main or intermediate)
conclusion follow from the reasons which are given for it?’
4 Explain why the conclusion does not follow; i.e. think of a reason why the
conclusion might not be true, even if the reason(s) are true, and try to do this by
referring to the subject matter of the argument, and not merely stating the name
of a fallacy.