The structure of arguments

The reasons in an argument can fit together in a number of ways. Sometimes there may be
only one reason supporting a conclusion, for example:
Falstaff is thinner. So he has probably been dieting.
In our original Falstaff argument, there are two reasons:
Reason 1: People who diet lose weight.
Reason 2: Falstaff hasn’t lost weight.
These two reasons, taken together, support the conclusion:
Falstaff cannot have dieted.
Neither reason on its own would be sufficient to support the conclusion. The number of
reasons used in this way in an argument need not be limited to two. An argument could
have three, four or a whole string of reasons which need to be taken together in order to
support the conclusion.
However, sometimes when there are two (or more) reasons, they are offered not as jointly
supporting the conclusion, but as independently supporting it, for example:
It is right to ban cigarette advertising because it encourages young people to start
smoking. But even if it had no such influence on young people, it would be right to
ban it because it could give existing smokers the mistaken impression that their
habit is socially acceptable.
In this case, the conclusion that it is right to ban cigarette advertising could be supported
either by the claim that it has the adverse effect of encouraging young people to start
smoking, or by the claim that it has the adverse effect of making smokers think that their
habit is socially acceptable. This differs from the Falstaff argument in that the author of
this argument does not regard it as necessary to offer both reasons, and would claim that
the argument had established its conclusion if either reason could be shown to be true. But
when an argument offers reasons as jointly supporting the conclusion, then evaluating the
argument requires an assessment of the truth of all the reasons.
In the two examples we have just presented, it is clear that in one case joint reasons, and
in the other case independent reasons, are being offered. But in some arguments it
will be debatable whether the reasons are intended to support the conclusion jointly or
independently. Consider the following example:
Our 40,000 GIs stationed in South Korea support a corrupt regime. The savings in
dollars which would result from their coming home could make a sizable dent in the
projected federal deficit. Furthermore, the Korean conflict ended 30 years ago.
Hence it is time we brought our troops home.
In this case each one of the first three sentences presents a reason for the conclusion, which
appears in the last sentence. Because they are all quite strong reasons for the claim that the
troops should be brought home, it may be that the author regards them as independently
supporting the conclusion. On the other hand, if they are taken jointly, they present a
much stronger case for the conclusion. We could interpret the argument either way here,
but it should be remembered in cases like this that, provided all the reasons are true, the
argument could be judged to be stronger if it is regarded as presenting joint rather than
independent reasons.
Arguments can become much more complicated than the above examples. Reasons may be
offered for a conclusion which is then used, either on its own or together with one or more
other reasons, in order to draw a further conclusion. It is useful to make a distinction in
such cases between an intermediate conclusion and a main conclusion. Here is an example of
an argument with an intermediate conclusion.

A majority of prospective parents would prefer to have sons rather than daughters.
So, if people can choose the sex of their child, it is likely that eventually there will
be many more males than females in the population. A preponderance of males in
the population is likely to produce serious social problems. Therefore, we should
discourage the use of techniques which enable people to choose the sex of their
child.
The main conclusion here, signalled by ‘Therefore’, is that
we should discourage the use of techniques which enable people to choose the sex of
their child.
The immediate reasons given (jointly) for this are:
if people can choose the sex of their child, it is likely that eventually there will be
many more males than females in the population,
and
a preponderance of males in the population is likely to produce serious social
problems.
The first of these two reasons is itself a conclusion, signalled by the word ‘So’, which
follows from the basic reason:
A majority of prospective parents would prefer to have sons rather than daughters.
Thus an analysis of this passage reveals that the first sentence is a basic reason, which
supports the intermediate conclusion expressed in the second sentence, which in turn, taken
jointly with the additional reason offered in the third sentence, supports the main con-
clusion in the last sentence. Unfortunately, not all arguments will set out their reasons and
conclusions in this obvious order of progression, so you cannot simply take it for granted
that basic reasons will always appear at the beginning, with intermediate conclusions in the
middle and main conclusion at the end.
We have mentioned two important approaches to identifying the reasons which are being
offered in an argument – first, asking what kind of reason could give support to a particular
conclusion, and second, attempting to sort out the way in which the reasons in a
passage hang together. It may seem that detailed knowledge of the subject matter will be
necessary before one can begin to analyse the argument, and no doubt it is true that the
more familiar you are with the subject matter, the more readily will you be able to work
out the structure of the argument. However, on many topics, most people will be able to
go a long way towards understanding arguments which they encounter in newspapers and
textbooks, and they will improve at this task with the kind of practice afforded by the
following sets of exercises.
Summary: Identifying reasons in an argument
1 Look for reason indicator words, i.e. words such as ‘because’, ‘for’, ‘since’ ‘if
. . . then’.
2 Identify the conclusion and ask ‘What kind of reason would I have to produce
in order to support this?’
3 Reasons may be items of common knowledge, general principles, reports of
results from experiments, statistics, etc.
4 Reasons can be offered as jointly or as independently supporting the
conclusion.
5 Some reasons also function as intermediate conclusions.