In some arguments, such as [4] or [5], what is assumed is a matter of opinion. You could easily imagine someone who initially thought freedom of information was a good thing changing her mind after seeing websites that encourage violence, racism or gross indecency.
You could also imagine someone moving the other way and deciding that freedom of information is a good thing, and that it should be encouraged even if some minority groups abuse it.
But in other cases the assumptions we make are more deeply rooted or unshakable.
Many arguments make assumptions based on strong beliefs, strict laws, political leanings, or shared cultural attitudes and loyalties that we grow up with and keep for a lifetime. Realising when an argument rests on assumptions which we take more or less for granted, and rarely question, is an important part of critical thinking and intelligent debate.
opposite assumption that no one has the right to own a piece of land and keep others from using it, especially a large estate like the Steinbergs’. Many people seriously question the assumption that trespass is morally (and not just legally) wrong, or that trespass laws are just laws, or that anyone needs ‘permission’ to set up a home where they choose. One might argue that the Steinbergs showed a complete lack of compassion in prosecuting the family:
that they used their money and power to evict underprivileged people, of minority ethnic status, for no obviously good reason other than exercising their legal right. Some might say that the Steinbergs have everything to be ashamed of, and certainly much more to be ashamed of than the travellers.
How you evaluate and respond to an argument like this depends very much on your own political and cultural assumptions.
But whichever side you take on the issues, you will not have dealt critically with the argument unless you have recognised and given thought to these assumptions as well as the explicit premises.
The fact that the author assumes all this rather than stating it, or offering any argument for it, indicates that he or she simply takes it for granted, and no doubt expects that many if not all readers will do the same. In the culture to which the author belongs there are laws that protect property and punish trespass, and the majority accept such laws because it is in their interests to do so. Laws that prevent travellers from setting up home wherever they like also prevent them from moving into your house or setting up camp in your front garden.
Consequently, people who own or rent homes of their own tend to accept such laws, and assume they have some moral backing, even if at times they seem harsh. The author does not see any need to spell all this out or argue for it.
It ‘goes without saying’.
But that doesn’t mean the argument or its assumptions cannot be challenged. Not every social group adopts the same attitudes to private property as the author. There are people who choose to live, or would prefer to live, nomadic lifestyles without permanent homes, who might start from the entirely
Summary
• An assumption, under the ordinary meaning of the word, is a claim or belief that is presumed true, without necessarily being warranted or justified.
• The premises of many arguments are assumptions. In other words the conclusion of an argument often rests on one or more assumptions. If the assumption can be shown to be false or unwarranted, then the argument must be judged unsound.
• Some assumptions that are made in the course of an argument are implicit rather than openly stated.
• Calling a claim or belief an assumption means that it is questionable, open to challenge, or in need of justification. It does not mean that it is necessarily false or unacceptable.
• Some assumptions reveal deep-rooted beliefs or attitudes.
alcohol sweet and fruit-flavoured you are encouraging children to drink it.
Therefore its sale should be banned.
A Alcopops were manufactured specially to appeal to children.
B Children of an early age do not like the taste of alcohol.
C Children like the taste of sweet, fruit-flavoured drinks.
D Sweet drinks do not appeal as much to adults as to children.
OCR 2 Read the following argument and suggest
one or more hidden assumptions that it relies on:
The internet has brought many advantages. It is a wonderful source of knowledge and, used intelligently, it provides for a healthy exchange of views. But history will prove that the internet is a far greater force for harm than for good. Its great flaw is that the information on it is not, and indeed cannot be, regulated. Anyone can access it and anything can be published on it, freely and at little or no cost.
3 Do you agree or disagree with the following statement – and why?
Every argument must make at least one unstated assumption.
4 With reference to argument [6]:
Either have a class or group discussion and debate the motion:
The Steinbergs have nothing to be ashamed of in evicting the travellers from their land.
Or write a short argument for or against the above motion.
Answers and comments are on pages 314–15.
1 Study each of the following arguments and say which of the multiple-choice options below it are implicit assumptions on which the argument depends. To make it more interesting, there may be more than one right answer.
a Raisa will hate this book. For a start it’s non-fiction, not a novel. But worse still it’s all about mountain-climbing.
A Raisa hates non-fiction.
B Raisa hates mountain-climbing.
C Raisa likes novels.
b Nashida is claiming compensation from her former employers on the grounds that she was forced to leave her job.
The employers are saying that they did not actually dismiss Nashida. However, they do admit that they altered the terms and conditions of her job. The law allows that, if employees are forced to accept changes in their working conditions that mean they would suffer as a result, and for that reason only they choose to leave, then their entitlement to compensation is the same as if they had been dismissed. Therefore Nashida’s claim should be upheld.
A Nashida would have suffered as a result of the changes to her job.
B Nashida had done nothing to deserve dismissal.
C Nashida would not have left if the job changes had been favourable.
D Nashida had no choice about the changes that were made to her job.
OCR (adapted) c ‘Alcopop’ is the name given to a range of drinks that contain alcohol but taste like fruit drinks. Their sale in the shops has been blamed for a recorded rise in alcohol consumption by children and young people, and with good reason.
It is common sense that if you make
End-of-chapter assignments
‘fallacies’. A fallacy is a flawed line of
reasoning. Because it is very often not possible to know the truth or otherwise of the
premises, most of the critical evaluation of arguments focuses on the reasoning, and whether it is sound or fallacious. (If you know that either the reasons or the conclusion is false, there is no further critical thinking to do on the argument!)
Note: the word ‘fallacy’ is often used casually to mean a false or mistaken claim.
For example, after 1912 a person might have said, ‘It was a complete fallacy that the Titanic was unsinkable.’ In critical thinking, or any formal context, ‘fallacy’ is never used that way. A fallacy is always a defective argument.
Read the following argument and decide whether or not the reasoning is flawed. If it is flawed, explain what you think the flaw is.
[1] The outstanding success of Amulk’s company, which was launched against the advice and without the support of bankers, business consultants and financiers, just goes to show that one person’s vision can prove all the experts in the world wrong. Anyone thinking of setting up in business should therefore trust their own judgement, and not be influenced by the advice of others.
Activity
Commentary
First we need to analyse the argument so as to identify the conclusion and the reasons. Then we need to ask whether or not the conclusion follows from the reasons, according to Rule 2.
A good argument is one that satisfies two rules.
Rule 1 is that the reasons should be true.
We cannot trust an argument that is based on false premises. If we know that one or more of the premises are false, we must reject the argument.
Rule 2 is that the conclusion must follow recognisably from the reasons, meaning that if the reasons are all true, the conclusion cannot be false.
An argument that passes both these tests is said to be sound. An argument that fails one or both of them is unsound. Interestingly we use the same words to talk about structures like boats or buildings, and more abstract objects such as ideas, advice or plans. When you describe something as sound, what you are saying about it is that it is safe, reliable, free of faults. You would not call a boat sound if it had a hole in it and sank ten minutes after setting off from the shore. You would not call a plan sound if it led to a disaster. And you don’t call an argument sound if it leads to a false or dubious conclusion. (A bad argument is often said to have a hole in it – something missing from the reasoning.) Nor do you call an argument sound if you know, or have reason to believe, that one or more of its premises are false.
Another word for an unsound argument is
‘flawed’. A flaw is a fault. There are two main ways in which you can find fault with an argument. You can disagree with one or more of the reasons; and/or you can show that, whether the reasons are true or not, the conclusion doesn’t follow from them.
Arguments that are unsound for this second reason are said to contain ‘reasoning errors’, or
‘flaws in the reasoning’. They are also called