- Slides: 85
Critical Thinking 1) Understanding the nature of arguments 2) 2) Reliable and unreliable arguments
Critical Thinking We all argue but how well do we do it? Are the arguments ‘sound’ or merely opinions with little factual basis?
Critical Thinking Look at the following four arguments. Which of these are well structured?
Critical Thinking We had to go to war, because: If Saddam Hussein had gained chemical weapons he either would have used them or made them available to terrorist organisations. Saddam Hussein was developing such weapons. We could not allow him to gain such weapons. Therefore, we had to prevent him from doing so, either by peaceful means or by going to war. We could not do it by peaceful means.
Critical Thinking Those who would allow Saddam to develop horrendous weapons in light of his previous use of chemical weapons against the Kurds are naïve pacifists. War is a necessary evil – we cannot let madmen do what they want just because we do not want to get our hands dirty. Remember what happened in 1939!!
Critical Thinking Blair is just Bush’s poodle, and GWB was just out to finish his dad’s work. It’s all about American imperialism and the desire for control of oil. Anyone who thinks that war is ever a good idea is playing into the hands of the American military-industrial complex.
Critical Thinking By going to war, the coalition was able to oust Saddam Hussein. Ousting Saddam Hussein was a good thing. However, by going to war, it is likely that the entire Middle East will be further destabilised, fundamentalism will grow, and religious intolerance will increase. These consequences outweigh the benefits of ousting Saddam Hussein. Therefore, we should not have gone to war.
Critical Thinking There are three main reasons for developing our critical skills. They are…
Critical Thinking 1) Avoid being led into error by others. 2) 2) Develop skills that will increase our skills of persuasion. 3) 3) The pursuit of truth.
The Wason & Johnson-Laird Test Exercise 1 (p. 5) How do we solve this problem?
The Wason & Johnson-Laird Test Don’t worry if you got it wrong or didn’t know. In the original test, only 5 out of 128 USA college students got it right. By the end of the unit you will know the answer.
The ‘Conjunction Fallacy’. Jacob is a 35 year old exphilosophy student who is politically active and highly intelligent. While at university, he was very active in the animal rights movement. Which is more likely?
The ‘Conjunction Fallacy’. 1) Jacob is a computer programmer for a large multinational company. 2) Jacob is a computer programmer for a large multinational company and a vegetarian. 3) (85% will get it wrong).
1) The purpose of an argument Philosophy is about being able to evaluate the arguments for and against beliefs i. e. the existence of God or the killing of animals. If we cannot do this we will never be able to put across good arguments.
Purpose of argument We need to be able to 1) Provide others with good reasons to accept a claim you believe to be true. 2) Evaluate whethere are good reasons to accept/reject claims put forward by others.
Purpose of argument Philosophy is as much concerned with why we might believe something as it is with what it is we believe. Look at the following discussion
Purpose of argument John: it is wrong to kill animals, even to eat them. Kevin: no it isn’t. There’s nothing wrong with eating them, hunting them or using them for sport. John: That’s rubbish. Kevin: Watch it or I’ll give you a slap.
Purpose of argument This is an important area in philosophy: morality or what should be or could be. However, it is a bad argument. But why? Look at this argument
The purpose of argument Lucy: There is never any good reason to kill animals. Mira: Not true. Sometimes humans need to kill animals in order to survive. Animals sometimes attack people and sometimes we have to kill them for food.
Purpose of argument Lucy: Maybe: but you are assuming that human life is more valuable than the lives of animals. All life is equally important. Mira: Human life is more valuable because we are more developed than animals. We suffer more, think more and feel more.
Purpose of argument Did you notice the differences? Instead of just stating a view they start to offer reasons for their beliefs. They also start to engage with the claims made by the other and respond to it. This is philosophical thinking.
Purpose of argument Critical Thinking involves the study of ‘arguments’ and not shouting matches or fights. So what is a good argument?
Spotting arguments Exercise 2 (p. 8) Which of the following do you think contain arguments? For each passage, try to explain the answer you gave
2) The distinction between arguments and statements a) Statements b) Arguments are made up from statements (claims, propositions). When someone makes a statement they assert that something is the case.
2) The distinction between arguments and statements a) Statements b) Statements, are therefore, true or false. c) Here are some statements:
2) The distinction between arguments and statements a) b) c) d) e) f) g) Statements Snow is white The sky is blue Edinburgh is the capital of Wales Bolivia is larger than Argentina God exists Celtic are the best team in the world
2) The distinction between arguments and statements There are many statements which we cannot tell if they are true or not i. e. ‘there is life on at least three planets in distant galaxies’. This is either true or false but how can we tell? Let’s look at other language.
2) The distinction between arguments and statements Assertions or statements – the door is open. Commands or imperatives – open the door. Questions – who is the tallest in the room? Expressions of emotion – Mmm, lovely
2) The distinction between arguments and statements Commands, questions and expressions of emotion or feeling are not statements because they cannot be true or false. In order for a sentence to be a statement it must be true or false. We need to be able to recognise this. Exercise 3 (page 10)
2) The distinction between arguments and statements b) Arguments must have reasons to support them. Think back to the argument between Lucy and Mira (p. 7). Both give reasons for their beliefs.
2) The distinction between arguments and statements b) Arguments All of Mira’s claims are statements. We can think of an argument as a list of statements linked together. The point of this is to produce a conclusion that will be true. An argument is designed to prove the truth of a particular claim. Here are some examples of arguments.
2) The distinction between arguments and statements b) Arguments (p. 11)
2) The distinction between arguments and statements b) Arguments These arguments because they are attempting to prove that a statement is true or false. The statement after the word ‘therefore’ is the conclusion of the argument.
2) The distinction between arguments and statements b) Arguments To prove some claim, is to demonstrate why it must be true, given that other things are true. Let’s think about Alice again.
2) The distinction between arguments and statements b) Arguments All humans are mortal (true) Alice is human (true) Therefore, Alice is mortal (true) The conclusion is true because the statements are true.
2) The distinction between arguments and statements b) Arguments The major difference between statements and arguments are: Statements are asserted Arguments offer proof in their conclusions
2) The distinction between arguments and statements b) Arguments If we reject the truth of a statement we deny it If we offer an argument against it is an attempt to refute it. Look at the following example
2) The distinction between arguments and statements b) Arguments ‘Smoking is good for your health’. To say ‘No, it’s not’ would be to deny the statement. If someone said ‘No it’s not – smoking causes cancer, which can kill you’ they would be attempting to refute it.
2) The distinction between arguments and statements b) Arguments When we reach a conclusion based on other claims that feature in the proof, we are said to infer (deduce or draw) the conclusion. ‘I infer from the fact that Alice is human and the fact that all humans are mortal, that Alice is mortal’.
2) The distinction between arguments and statements b) Arguments ‘Infer’ does not mean ‘imply’. To imply something is to hint at or suggest it. This is a common mistake, but a serious mistake nevertheless. Exercise 4 (page 12)
3) Argument structure As we have seen, the conclusion of an argument is the claim an argument seeks to prove. Statements used in the argument in support of the conclusion are known as premises. Lets look again at an example. (page 12)
3) Argument structure The writer is trying to convince his audience that it is Saturday – this is the conclusion of the argument. The writer does this in 2 ways a) If Doctor Who is on the TV, it must be Saturday b) Doctor Who is on TV. c) These are the premises of the argument.
3) Argument structure Arguments can have any number of premises The premises need not be true. A false premise (Edinburgh is in Wales) doesn’t mean it’s not an argument because the conclusion can still be true (p. 12). It would be tempting to think that good arguments will be those with true premises and a true conclusion but this is not always the case. Look at the following:
3) Argument structure Grass is green (premise) Snow is white (premise) Therefore, all dogs are mammals (conclusion) This includes two premises and a conclusion, so by the above definition it should count as a good argument – but it clearly isn’t. Why?
3) Argument structure 1) Hidden or Implicit premises Some premises remain unstated in everyday arguments – usually because everyone accepts them. ‘I think murderers should be hanged. That way they will not be able to commit murder again, and the existence of capital punishment will deter others from taking life from another human being’.
3) Argument structure 1) Hidden or Implicit premises What is the hidden or implicit premise? If you are dead, you cannot kill. Not if you live in Buffy the Vampire Slayers world, or Resident Evil The point is, that unless we state hidden or implicit premises, we will be unable to fully evaluate the argument in question.
3) Argument structure So, grass is green (true) Snow is white (true) Therefore, all dogs are mammals (true) These premises do not give us any reason or justification to believe the conclusion is true.
3) Argument structure The structure or form of the argument is very important as this provides the truth of the premises and the truth of the conclusion. Lets look at an example. (page 14)
3) Argument structure (p 1) If I work hard, then I will pass my exam (p 2) I did work hard Therefore (c) I will pass the exam Look at Para 4 & 5 on page 14
3) Argument structure It is very easy to identify the premises and the conclusions of the examples we have looked at so far. But in everyday life this is not always the case. Let’s look at 2 examples. (pages 14 & 15)
3) Argument structure See if you can spot: The premises The conclusion The implicit premises The structure/form of the argument
3) Argument structure ‘Freedom of speech is more important to society than the offence certain books might cause to individuals. People can be offended by anything, from nudity and bad language to trivial things, such as a person’s choice of clothes or haircut. This shows that we should not ban books solely because they cause offence’.
3) Argument structure ‘A baby is a lovely little gift from above. Who would ever want to refuse a gift, especially one from such a glorious benefactor? If something is a gift from above, then it should not be refused. That’s why contraception should be banned. It would be like refusing a lottery win or a free two-week holiday abroad’.
3) Argument structure Conclusions can appear at the end, in the middle or at the beginning. We must be able to identify it where ever it appears. In the first example, ‘this shows us that’ leads us to see that the statement following this ‘we should not ban books solely because they cause offence’ is the conclusion.
3) Argument structure Other phrases that can help might be: ‘therefore’, ‘thus’, ‘this demonstrates that’ or ‘we can conclude’. And although this does not work every time it will help us establish the claims within the argument through their connections.
3 a) ‘If…then. . . ’Conditional statements ‘If and then’. By asserting that ‘if’ (something-or-other) is true (or happens), ‘then’ (something else) will also be true (or will happen), the speaker is drawing a link between the two things. (p. 12 (B) & (D)) Some examples (page 16)
3) Argument structure • • If 2+2=4, then 4 -2=2. If the Conservative Party wins the election, then Tony Blair will not be PM. If Edinburgh is in Scotland, then it is in Britain. If I let go of this pen, it will fall to the floor. If I steal that book, then I will have committed a crime. If I go to visit my granny, I will not be going to the cinema. If I am dreaming, then this is not real.
3) Argument structure What is being claimed here? There is a direct connection between the two statements, namely that if the first statement is true, then so is the second. ‘If I let go of this pen, it will fall to the floor’.
3 a) Conditional statements • If…then… statements are known as conditional statements because the truth of the second claim is conditional on the truth of the first. • I didn’t pass the exam (p 2) • If I had worked hard, then I would have passed the exam (p 1)
3 a) Conditional statements • The statement on which the connection is conditional – the one introduced by ‘if’ is called • The antecedent
3 a) Conditional statements • The other – coming after ‘then’ is called • The consequent
3 a) Conditional statements • When the first statement is true, so is the second. So… • If 2+2=4 it is also true that 4– 2=2 • There is no suggestion that the first causes the second or makes it true: the claim is that if the antecedent is true, then, so is the consequent. • All conditional statements have this form.
3 a) Conditional statements Conditionals often feature in arguments such as (B) p. 12. (p 1) If Dr. Who is on TV, it must be Saturday (p 2) Dr. Who is on TV Therefore (c) It must be Saturday
3 a) Conditional statements There are two premises in this argument Given the first premise, we need the second premise, in order to have the right to infer the conclusion Sometimes the ‘then’ is left unstated and we need to look out for this
3 a) Conditional statements Do conditionals tell us anything else? Assume that (p 1) is true – ‘if Dr. Who is on TV, it must be Saturday’. But… What if you are told it is not Saturday? (Forget that it could be a repeat or on Sky). What can we infer from this?
3 a) Conditional statements Exercise 5 – Conditional statements 1 (page 17)
3 a) Conditional statements There are two legitimate conclusions that we can draw based upon a conditional statement. If we know the conditional and know that the antecedent is true, then we can infer the consequent (p 1) If Dr. Who is on TV, it must be Saturday (p 2) Dr. Who is on TV Therefore (c) It must be Saturday - BUT
3 a) Conditional statements If we know the conditional and know that the consequence is false, then we can infer that the antecedent is also false (p 1) If Dr. Who is on the TV, it must be Saturday (p 2) It is not Saturday Therefore (c) It is not the case that Dr. Who is on TV
3 a) Conditional statements If we know the conditional and know that the consequent is true, does this tell us anything? (p 1) If Dr. Who is on TV, it must be Saturday (p 2) It is Saturday (c) Dr. Who is on TV N 0, NO, NO But Why?
3 b) ‘Or’ statements ‘Or’ is often used with ‘either’ • The baby will be male or it will be female. • Either John will win the election or David will. • You can have the chocolate or the cake. • I will go to the cinema or the concert. • To gain entry to the college, you need three Bs or two As. • I will become a teacher or a social worker.
3 b) ‘Or’ statements Such statements have an important place to play within critical thinking. Just as with conditionals, this is because they serve to connect the truth of two statements, although in a very different way from ‘if… then…’. Rather than saying that the second statement is true if the first is, ‘or’ statements claim that at least one of the statements is true. So the following are true:
3 b) ‘Or’ statements • • • Either the Allies won the war in Europe or Germany and Italy did. Either Tony Blair won the election or Michael Howard did. Killing is always wrong or it is not always wrong. Lee Harvey Oswald shot John Fitzgerald Kennedy or someone else did. You can get into university with three Bs or you can get into university with 2 As.
3 b) ‘Or’ statements In critical thinking or connects two statements: I will get Mr. Fyfe for philosophy or I will get Mr Cassie
3 b) ‘Or’ statements • These are not true • The moon is made of cheese or it is made of glass. Edinburgh is in Germany or it is in France. Killing is always acceptable or theft is always acceptable. • •
3 b) ‘Or’ statements • But we have to be careful of ‘or’ in arguments • (page 20)
3 b) ‘Or’ statements • Exercise ‘Or’ statements • (page 21)
3 c) ‘And’ statements • • • These statements are also known as conjunctions They are used to join two statements (try to explain why!) Statements joined by ‘and’ are called conjuncts
3 c) ‘And’ statements • Some examples (p 22) Grass is green and snow is white. Grass is green and snow is purple. 2+2=5 and 3 -1=3. Ask yourself: which of these are true?
3 c) ‘And’ statements It seems that only the first of these sentences is true – why? It is the only example that has two true statements joined by ‘and’. An ‘and’ statement can only be true when it contains two true statements
3 d) ‘all’ and ‘some’ • The fourth group of statements we will consider here are those using the words ‘all’ and ‘some’. These words are called quantifiers, as they are used to discuss quantities – more than one example – of a particular kind of thing: all dancers are fit; some animals lay eggs; some Scots can speak Spanish; all Spaniards can speak Spanish
3 d) ‘all’ and ‘some’ • Exercise p. 23 & 24
3 d) ‘all’ and ‘some’ • Exercise p. 27 & 28
4. Recognising everyday arguments • A baby is a lovely little gift from above. Who would ever want to refuse a gift, especially one from so glorious a benefactor? If something is a gift from above, then it should not be refused. That’s why contraception should be banned. It would be like refusing a lottery win or a free two-week holiday abroad!
4. Recognising everyday arguments • Exercise p. 29 & 30 • Conclusions for everyday arguments