Identifying Assumptions

1. Identifying Assumptions

2. Assumptions What is the meaning of the word assumption? In ordinary language the word assumptionmeans something which is taken for granted but is not stated. For example, I may assume when I get on an aeroplane that the pilot ahs been trained and is qualified to fly the machine safely with me and the other passengers in it. I do not feel the need to go and ask to see the pilot’s license or checkup on their history. I am making an assumption. It is probably a very safe assumption, but it is not based on conclusive evidence. .

3. However in Critical Thinking Paper 1 the word ‘assumption’ means that part of the argument that is not stated, but is neededin order for the argument to work i.e. it is another reason that is needed for the argument to make sense

4. Assumptions come in two forms: Underlying Assumptions or sometimes referred to as Implicit Assumptions (Paper 1) Or Unstated Assumptions or sometimes referred to asExplicit Assumptions (Paper 2)

5. In Critical Thinking an underlying assumption works in two important ways: • First in giving support to the basic reasons presented in the argument • Second as a missing step within the argument • perhaps as an additional reason which must be added to the stated reasons in order for the conclusion to be established or • perhaps as an intermediate conclusionwhich is supported by the reasons and in turn supports the main conclusion.

6. Therefore an argument rests heavily on the underlying assumption, as it does the stated reasons, to establish the conclusion. Without the underlying assumptionthe argument will fail.

7. R1 Example If cigarette advertising were banned, cigarette manufactures would save the money they would otherwise have spent on advertising. Thus, in order to compete with each other, they would reduce the price of cigarettes. So, banning cigarette advertising would be likely to lead to an increase in smoking. Think about the reasoning. What conclusion is the author trying to get us to accept? What basic reason does he offer? Is there an intermediate conclusion? Can you identify a stage in the argument whichhas not been stated i.e. an underlying assumption/missing reason? MC IC

8. The argument starts with a basic reason: If cigarette advertising is banned, cigarette manufacturers save the money they would otherwise have spent on advertising. and from this draws the intermediate conclusion: Thus in order to compete with each other, they reduce the price of cigarettes. It then draws the main conclusion: So banning cigarette advertising leads to an increase in smoking.

9. The MC would not follow from the IC if a reduction in the price of cigarettes made no difference to the numbers of cigarettes bought and smoked. So an assumption underlies this move – that if cigarettes were cheaper, smokers would smoke more, or non-smokers would become smokers. The conclusion does not say exactly what it means by ‘an increase in smoking’, so we cannot be sure whether the assumption is If cigarettes were cheaper, smokers would smoke more, or If cigarettes were cheaper, more people would smoke. But it will require one of these assumptions that is underlying the argument to support the MC. So the underlying assumption taken together with the IC gives support to the MC of the argument.

10. Let’s look at this example: Advances in fertility treatments will soon allow parents to choose the sex of their child. This will have serious consequences for society, as there will be more unemployed young men and, as most car accidents are caused by young men, the number of car accidents will rise. The argument links choice about the sex of a child to problems related to having more boys than girls. The argument therefore rests on the idea that parents will chose boys in preference to girls. We would say that the assumption is that parents would choose boys in preference to girls if they are allowed to choose the sex of their child. You may have realized this without even thinking about it, but the key point is that the argument falls to pieces without this assumption. C R1 R2

11. R1 R2 Example 3 One third of the population still smokes. Everyone must know that smoking causes lung cancer and heart disease. So knowing the dangers of smoking is not sufficient to stop people from smoking There are two basic reasons here. Is there a missing step, a missing reason here that is giving support to the argument? Yes. The claim that ‘everyone must know…’ suggests that there is an underlying reason for expecting people to be well informed on this topic so the assumption made is that there has been widespread publicity on the dangers to health of smoking – on television, in newspapers and by means of posters in the waiting rooms of doctors, hospitals etc. C

12. So when identifying underlying assumptions remember that: An underlying assumption is one that is needed to support a conclusion or validate an argument. An underlying assumption is necessaryfor accepting the conclusion.

13. An underlying assumption is a missing premise/reason. An underlying assumption is part of the structure of the argument. An underlying assumption can be challengedjust like any other premise.

14. Look at the argument given: Ben: Asha’s gone home early. Cal: What makes you say that? Ben: Her car’s not in the car park. What is Ben’s argument? Ben’s argument is that Asha has gone home early. The reason he gives is that her car is not in the car park.

15. Is there anything extra that Ben is assuming when he draws his conclusion? He is assuming a lot. He is assuming that Asha has not gone somewhere other than home. He is assuming that no one else drove the car out of the car park. Yet another assumption he is making is that she came in her car that day. All of these assumptions Ben makes are unstated assumptions or explicit assumptions. They are not needed to come to the conclusion that Asha has gone home early.

16. What is needed to come to the conclusion and to accept the argument that Ben makes, is to make the assumption that Asha herself took the car home. Accepting that Asha drove the car herself is therefore necessary to the argument which fails completely without it. That is why it is called an underlying assumption.

17. Young people are not very interested in politics and tend not to vote. Most people who do vote are the older, well-off people. Governments tend to represent the interests of those who have voted for them. Elected governments, therefore, do not represent all sections of society. Politicians should change their approach to ensure that more young people vote. This argument rests on the idea that governments should represent all sections of society. In other words, the argument relies on an assumption that governments should represent all sections of society. R1 R2 R3 R4(IC) MC

18. This example again shows clearly that an assumption is part of the structure of an argument. To be more precise: assumptions are a missing stepin the argument, a missing reasonthat the argument needs in order to support the conclusion. It is the missing reason between the other reasons and the conclusion. You can see this more clearly if we write the assumption into the argument as follows:

19. R1 Young people are not very interested in politics and tend not to vote. R2 Most people who do vote are older, well-off people. R3 Governments tend to represent the interests of those who have voted for them. R4(IC) Elected governments, therefore, do not represent all sections of society. R5(UAssumption) Governments should represent all sections of society. MC: Politicians should change their approach to ensure that more young people vote. The underlying assumption now acts as the fifth reason in the argument.

20. Recent research has shown that a foetus can hear at 30 weeks old. Computer-generated white noise was played to foetuses between 23 and 34 weeks old. Ultrasound scanning did not pick up any response under 30 weeks old but it did detect heart and movement responses in the 30- 34-week-olds. This fits with the fact that a baby’s hearing develops in the 30-34 week period. Given this new knowledge, we should encourage pregnant women to play music to their babies. R1 R2 R3(IC) MC

21. Which of the following is an underlying assumption of the above argument? • Heart and movement responses cannot be detected in foetuses under 30 weeks old. • Foetuses over 30 weeks old can distinguish between different types of sound. • Foetuses are particularly responsive to computer-generated white noise. • Hearing sounds such as music is beneficial to a foetus of at least 30 weeks old.

22. Heart and movement responses cannot be detected in foetuses under 30 weeks old. It is not A. This statement is not in the passage, in that we know that we can detect movement in the 30-34-week-old foetuses but not what the results were below this age. However, even if this statement were true, it would tell us nothing about whether or not we should encourage women to play music to their babies. It is a statement that is not in the passage, but it is not a missing step in the argument.

23. B. Foetuses over 30 weeks old can distinguish between different types of sound. It is not B. The argument is about sound in general; whether particular types of sound can be detected does not really mater. All we need to know is that babies can hear. And we are told this in the passage – their hearing develops at 30-34 weeks. This statement therefore, is not an assumption either.

24. C. Foetuses are particularly responsive to computer-generated white noise It is not C. This is a bit like A, in that it may be true or not and is certainly not in the original passage. However, the conclusion is about playing music to babies in the womb, so again we have a statement that is not in the original passage, but is not needed for the argument to work, which means it is not an assumption.

25. D. Hearing sounds such as music is beneficial to a foetus of at least 30 weeks old. D is the correct answer. By stating that there is a benefit to foetuses we suddenly are given a reason why pregnant women should play music to their unborn babies. This is the missing step in the argument – in other words the underlying assumption that is needed to make the argument.

26. R1 R2 C Many people today think that museums should be like private companies, concentrating only on activities which are profitable. In this way, it is seen as acceptable for museums to ignore the unfashionable or less popular parts of our history. The proper function of museums, however, is to provide a balanced picture of our history. Therefore we must ensure that they are subsidized by the state rather than having to worry about being profitable. .

27. Which one of the following is an underlying assumption of the above argument? • Museums cannot be run like private companies. • The government is prepared to subsidies museums. • Only museums can provide a balanced picture of our history. • Museums cannot provide a balanced history without state subsidy. • Museums which give a balanced picture of our history are more likely to be profitable.

28. Museums cannot be run like private companies. A is not assumed. The passage does not suggest that museums cannot be run like private companies but that they should not be run in that way for the reasons given. If they could not be run like private companies there would not be no need to ensure that they were not. A would be a very odd assumption to make and therefore can be safely ruled out.

29. B. The government is prepared to subsidies museums. B is not assumed either. The argument is trying to show that the government should subsidize museums. It does not take for granted that the government is prepared to subsidize them. You can argue that the government ought to do something even if you know they have no wish or intention to doe so.

30. C. Only museums can provide a balancedpicture of our history Cis nor assumed. There could be many other institutions – publishers, libraries, universities and so on – that could provide balanced histories. Museums are not the only possible providers.

31. E. Museums which give a balanced picture of our history are more likely to be profitable. E is not assumed. The author contrasts museums that simply concentrate on being profitable with museums carrying out their main function of providing a balanced picture of our history. If anything, the author sees museums that provide a balanced picture of our history as less likely to be profitable. E therefore contradicts the other premises rather than underlying them. No claim that contradicts a main premise could also be an underlying assumption.

32. In the days before the arrival of the Internet, publishers and booksellers effectively controlled what people read, since very few would-be authors could afford the high financial risks of publishing themselves. The Internet has changed all that. Now anyone can express views publicly, or distribute information, at little or no cost. Those who are fearful of the Internet should therefore stop dwelling on its faults, and acknowledge that its continued growth is, on balance, in the public interest, not against it. For, almost at a stroke, it has given us freedom of information on a scale that could never previously have been imagined. MC R1 IC (R2

33. Which of the following is the underlying assumption? • There is no reason for anyone to be fearful of the internet • Freedom of information is in the public interest. • In the past publishers and booksellers told authors what to write. • The internet will continue to grow • Everyone has the right to express any opinion.

34. The step from the intermediate conclusion to the main conclusion works only if we assume that freedom of information is itself in the public interest, since that is the sole reason given for saying that the Internet benefits the public. If it could be shown that on balance freedom of information was not in the public interest – i.e. that it did more harm than good – then the argument would be fatally damaged. B is the one that expresses this assumption. It states plainly ‘Freedom of information is in the public interest.’ none of the other claims is required for the argument to succeed.

35. A does not have to be assumed; there could be reasons to be wary of the Internet whilst still concluding that on balance it was a good thing. C Is not necessary for the argument. We are told that publishers, booksellers etc. may have controlled what was read by deciding to print this or sell that; but that is not the same as telling authors what to write.

36. D does not have to be assumed either. The argument is about whether the Internet is good for people, not how long it will last. It does not really even imply that it will last, though it is plainly the author’s hope that it will. Ecannot be assumed. It is beyond the scope of the argument, which claims only that the Internet gives people the ability to express their own opinions this does not imply that they have a right to express any opinion, as E claims.

37. C R1 R2 What is the key assumption underlying this argument? It has to be assumed that unregulated exchange of information is bad 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.

38. Homework Assignment Read Critical Thinking – John Butterworth. Chapter 9 - Assumptions