RECOGNISING IMPLICATIONS OF ARGUMENTS

Sometimes a whole argument has implications which go beyond the particular subject
with which it is concerned. There are two important ways in which an argument can do
this – by exhibiting a particular structure or shape, which it can have in common with
arguments on other topics, or by relying on a general principle which can be applied to
other cases. The skills involved in dealing with implications of arguments can be described
as recognising parallel arguments and recognising and applying principles.
Recognising parallel arguments
The value of this skill is that being able to recognise parallel arguments may help us to see
what is wrong with an argument. Sometimes it is easier for us to recognise a flaw in an
argument if the argument is about a familiar subject. Suppose you are presented with an
argument on an unfamiliar topic, and although you doubt your ability to assess the subject
matter, you can nevertheless see that the argument has a particular shape or pattern. If you
can substitute some familiar subject matter into this pattern, you may be able to see
whether the argument is good. Not all arguments can be dealt with in this way; those
which can tend to be relatively short, and to succeed or fail in virtue of their structure,
rather than because there is additional evidence which counts against them.

Someone who objects to an argument by saying ‘You might as well argue that . . .’ is often
presenting a parallel argument to show that there is a problem with the original argument.
This is what is happening in the two following examples of conversations:
James: I mean what I say because I say what I mean.
John: You might as well argue that you eat what you see because you see what you eat.
Sam: We have all had the experience of being deceived by our senses – the stick
which looks bent when it is straight, and so on – and all the information we get
through our senses in this way is potentially illusory, therefore sense experience
is always unreliable.
Jo: You might as well argue that since we’ve all had the experience of being lied to
– that even lovers lie and that everyone is potentially untrustworthy, therefore
no one can ever be trusted.
The argument presented in Exercise 5 (p.22) offers an example in which, if we construct
a parallel argument, we can see that an unwarranted inference has been made. The
argument concerned the claim that there is no justification for public discussion and
condemnation of the sex life of the US President. In order to persuade us that a husband
who deceives his wife can nevertheless be a good President, it gave examples of Presidents
who had been good husbands (in the sense that they did not deceive their wives) but bad
Presidents. We could summarise this section of the argument as follows:
Someone who does not deceive his wife can nevertheless be a bad President. So
someone who does deceive his wife can be a good President.
Although the conclusion here may be true, and although – especially if we agree with the
conclusion – we may be tempted to think that a good reason has been offered for it, in fact
the first sentence is not a good reason for accepting the conclusion.
This is evident if we look at the following parallel argument:
Someone who is not cruel to children can nevertheless be a bad child minder. So
someone who is cruel to children can be a good childminder.
We can immediately see with this example that the conclusion cannot be true, because
someone who is cruel to children cannot possibly be a good childminder. If the conclusion
must be false, then this cannot be a good argument even if the reason offered is true. The
reason no doubt is true, because in order to be a good childminder you have to do more
than merely refrain from cruelty to children. The argument is bad because the reason is
not sufficient to establish the conclusion, and if this is so with the argument about
childminders, then it is also the case with the parallel argument about US Presidents.
Whether or not a President who deceives his wife can nevertheless be a good President
depends upon whether the tendency to deceive extends to all areas of the President’s life. It
does not depend upon whether a President who is an exemplary husband deceives the
public about some of his actions.
Exercise: Identifying parallel arguments
In these multiple choice questions, you should pick the answer which uses reasoning
parallel to the reasoning in the original passage.
1 Because heroin addicts usually have one or more needle marks on their arms, and
Robert has some needle marks on his arm, it follows that Robert is probably a heroin
addict.
Which of the following most closely parallels the reasoning used in the argument
above?
(a) Because patients with malaria usually have high fevers, and George is a patient
with malaria, George probably has a high fever.
(b) Because patients with malaria usually have high fevers, malaria probably causes
high fevers.
(c) Because doctors have high incomes, and people with high incomes pay high
taxes, doctors probably pay high taxes.
(d) Because students are usually under twenty-five years old, and Harold is under
twenty-five years old, Harold is probably a student.
(e) Because heroin addicts usually have needle marks on their arms, most heroin
addicts probably inject the drug directly into their veins.
(Law School Admission Test, February 1986)
2 It has usually been claimed that in eras of high infant mortality, parents adopted
indifference to children as an emotional defence. But some scholars deny that parents
were indifferent to children because so many died, arguing instead that the children
died because their parents were so unconcerned about their children as to spare no
time for them.
Which of the following is most similar in its structure to the argument described in
the last sentence above?
(a) It was not the school’s new reading programme, but parents’ increased concern
with their children’s schoolwork that produced better reading scores.
(b) It is not true that the lack of qualified workers depresses wages in the poor
sectors of an industrial economy; rather, the low wages attract unskilled labour.
(c) It is not changing demand that prompts the introduction of new fashions;
actually the clothing industry brings in new fashions whether the public wants
them or not.
(d) It is not true that those who take illegal drugs harm only themselves; by supporting
organised crime, they harm society as well.
(e) It was not considered worthy of a poet to write for the Elizabethan theatre;
nevertheless, many poets did so.
(Law School Admission Test, June 1983)
3 The achievement of zero population growth in Great Britain has not forestalled the
recent political and economic decline of Great Britain. We must conclude that rapid
population growth is not the economic disaster social scientists have led us to believe
it to be.
Which of the following is most like the argument above?
(a) Many people who do not smoke cigarettes develop chronic respiratory illnesses;
therefore, cigarette smoking cannot be the health risk it is supposed to be.
(b) Jerry bought expensive paint but she still had to apply two coats to the wall to
cover the old colour; therefore, you might as well buy the cheapest paint available.
(c) Even if the country uses less energy this year than it did last year, more oil will
be imported than was imported last year; therefore, energy conservation should
be encouraged.
(d) This drug causes certain side effects in a small percentage of the population; we
can conclude that it is safe for the majority of people.
(e) Some of his paintings are dull and uninspired; we can conclude that he is not in
the same class as the greatest artists.
ANSWERS:

1 The answer is (d). They both have the following structure:
Because Xs usually have characteristic Y, and
because Z has characteristic Y, it follows that
Z is probably an X.
In the original argument,
X = heroin addict
Y = needle marks on their arms
Z = Robert
In (d),
X = students
Y = age of less than 25 years
Z = Harold
The structure of (a) is:
Because Xs usually have Y, and
because Z is an X,
Z probably has Y.
The structure of (b) is:
Because patients with X usually have Y,
X probably causes Y.
The structure of (c) is:
Because Xs have Y, and
because people with Y do Z,
Xs probably do Z.
The structure of (e) is:
Because Xs usually have characteristic Y,
most Xs probably do Z.
2 The answer is (b). The last sentence and (b) both reason as follows:
X did (does) not cause Y,
Y caused (causes) X
In the original passage,
X = high infant mortality
Y = the indifference of parents towards their children
In (b),
X = lack of qualified workers in the poor sectors of an economy
Y = low wages
The structure of (a) is:
It was not X which caused Y,
it was Z which caused Y.
The structure of (c) is:
X does not cause Y,
Y happens whether X happens or not.
The structure of (d) is:
Those who smoke cause harm to X and to Y.
The structure of (e) is:
It was not considered worthy for Xs to do Y,
but many Xs did Y.
3 The answer is (a). (a) and the passage both have the following underlying
structure:
In one case (or in some cases), the absence of X has not prevented the
occurrence of disastrous result Y.
Therefore, X does not have the disastrous results which it is supposed to have.
In the original passage,
X = rapid population growth
Y = political and economic decline
In (a),
X = smoking cigarettes
Y = chronic respiratory illnesses
(b) starts with a statement which could be seen as similar in structure to the first
statement of the original passage:
Using expensive paint (the absence of cheap paint) did not remove the need
to apply two coats (did not prevent disastrous result of having to apply two
coats).
But the conclusion of (b) makes no reference to cheap paint not having the disastrous
results it is supposed to have.
(c) could also be seen as starting off in a similar way to the passage:
Using less energy (the absence of high energy consumption) will not prevent an
increase in oil imports.
But there is no suggestion that using less energy has been claimed to have disastrous
results.
Neither (d) nor (e) even begins with a similar structure to the original passage.
(d) begins with: X causes Y for some Z
(e) begins with: Some X are Y and Z