Skip to the content | Change text size

The Monash Critical Thinking Study

Sample teaching materials: Reason!able argument mapping.

Extract from Lab 3 Student Handout

The structure of arguments

A. Independent and co-dependent premises

Independent premises are justifications that support the conclusions without relying on each other. So you could technically split the argument into two and the conclusion would still follow logically in each separate argument.

Co-dependent premises on the other hand rely on each other jointly to support the conclusion. These are sometimes called linked premises. What this means is that if you try to split the argument into two; each one of the premises alone would not be sufficient to provide a justification for the conclusion. They would however be sufficient to support the conclusion if you combined them.

Exercise 1

For each of the following passages:

1. Identify the conclusion of the argument

2. Identify the premises

3. State whether the premises are independent or co-dependent

***

1. Single-sex high schools work better than coeducational high schools because adolescents do better when they aren't distracted by the presence of the opposite sex. Also, the developmental needs of adolescent boys and girls are divergent.

2. City bus drivers who are using the new computerized fare collection system have a much better on time record than do drivers using the old fare collection system. Millicent Smith has the best on time record of any bus driver in the city. Therefore, she must be using the computerized fare collection system.

3. The capture of a wild animal is justified only as a last resort to save that animal's life. But many wild animals are captured not because their lives are in any danger but so that they can be bred in captivity. Hence, many animals that have been captured should not have been captured.

...

10. Economist: Interest rates should be reduced for several reasons: the economy is slowing down fast, many companies are in great difficulties and consumer demand has fallen off dramatically.

B. Sub-arguments

A sub-argument is an argument used to establish a claim which is then used as the premise of a further argument. The conclusion of that argument may then serve as a premise in another argument and so on, leading to a chain of argument.

Sub-arguments occur whenever a justification or objection is provided for one of the premises of a given argument. Both reasons and objections can occur at any point in a chain of argument.

Supporting arguments, objections and rebuttals are all examples of sub-arguments.

Exercise 2

For each of the following passages:

1. Identify the main conclusion of the argument
2. Identify the premise or premises used to support that conclusion.

3. For each of the premises you identified in 2, is any supporting argument given either for or against that premise? That is, is there a sub-argument for that premise?
4. If so, identify the premises of the sub-argument.

5. Repeat this process until you arrive at the unsupported premises of the argument.

***

1. There is a reason why famous athletes deserve their million dollar salaries. Their careers are over in just a few short years, so they don't have very long to make their money.

2. Increasing the size of a police force is only a stopgap method of crime prevention because it does not get at the root causes of crime. Therefore, city officials should not respond to rising crime rates by increasing the size of their city's police force.

....

Exercise 3

The following excerpts are from Chapter 3 of Singer's book and contain an extended analysis of President Bush's moral reasoning concerning stem-cell research. Your tutor will give you one or two of these excerpts to analyse. The aim is for you to create a map of the argument using the Reason!able software. Here are some guidelines to help you:

1. Start by reading the excerpt once over to get a general idea of what it says.

2. Identify the main conclusion of the argument. Enter this on your map.

3. Identify each of the premises of the main argument and enter these on your map.

4. Most of the excerpts contain a sub-argument - either further reasoning in support of a premise or an argument which supplies an objection to a premise of the main argument. The next step is to identify these sub-arguments.

5. Read over the excerpt again and check it against the map you have constructed? Does the map give a good representation of the argument? Is there anything important that you have left out?

Extract from Lab 3 Tutor's Notes

Exercise 2 Solutions

1. An argument chain:

argument chain

2. An argument chain

argument chain

Exercise 3 Solutions

Excerpt 1 - President Bush on using frozen embryos for stem-cell research

Bush's argument looks something like this:

bush 1

Excerpt 2 - The 'natural causes' argument

This is an objection to the main moral argument given by Bush:
bush 2

Excerpt 3 - The argument from uniqueness

This excerpt contains two objections to the 'uniqueness' argument. First Singer points out that it does not in general, follow from the fact that something is unique that it should be preserved (the snowflake is offered as a counter-example to this general claim). The second objection is not to this general principle but to an alternative principle that might lead to the same conclusion - that it is ''good for there to be more unique human beings'. This is objected to on different grounds. Here is one map representing both arguments and objections:

bush 3


Extracts from Lab 5 Student Handout

ARGUMENT EVALUATION: WHAT MAKES AN ARGUMENT SUCCESSFUL?

Really there are only two conditions an argument must satisfy in order for it to be successful:

1. The premises must be true

2. The premises must justify or support the conclusion

1. Truth

Examples

1. The earth is flat. So, if you sail too far in one direction you will eventually fall off.
2. All Englishmen are alcoholics. So, Prince Charles must have a drinking problem.

Can you think of any more examples?

Evaluating premises

How do you make a judgement about the truth of the premises? Sometimes you will know whether the premises are true, sometimes you might not be sure. What do you do in that case? Here are some questions you could ask:

It can help to establish the source or ground of the premise. When you judge that the premise 'the earth is flat' is false, how do you know this? Well, everyone knows that, it is common knowledge. 'Common knowledge' is one kind of ground. On the other hand, you might judge that a premise is true because you were told it was true by an expert in the relevant area. This is another type of ground,'expert opinion'. Knowing the ground of a premise can help you make a judgement about whether it is true or not. Here is a list of some grounds:

Can you think of any more?

Exercise 1

Where possible, identify the ground on which the premises in the following arguments are based:

1. That long term cigarette smoking can lead to health problems including cancer and lung disease is a scientifically well established fact. Contrary to what many people seem to believe, however, it is not necessary to deny this fact in order to reject the view that tobacco companies should be held either morally or legally responsible for the poor health of smokers. After all, excessive consumption of candy undeniably leads to such health problems as tooth decay, but no one seriously believes that candy eaters who get cavities should be able to sue candy manufacturers.

...

8 . Father Ted cannot be a real Christian. No one who can correctly be described as 'Christian' would lie, cheat, drink and steal as much as Father Ted.

***

2. Justification

REASONS

For a set of premises to count as a good REASON for a claim they must all be true and they must justify or support the claim:

A set of premises justifies or supports a conclusion when the following condition is satisfied:

If all the premises are true, then the conclusion is true.

How can you decide if this condition is satisfied? Here is a test you can use. Ask yourself:

Is it possible that the premises are true and that the conclusion false?

Here is another test (see Elements of Argument, pp. 45-7). Ask yourself:

If I believed the premises, would that increase my degree of belief in the conclusion?

OBJECTIONS

For premises to count as a good OBJECTION to a claim they must be true and they must oppose the claim.

Premises oppose a claim when the following condition is satisfied:

If all the premises are true, then the claim is false.

Equivalently, we can say that premises oppose a claim when the premises support the opposite (contradictory) of the claim.

How can you decide if this condition is satisfied? Ask yourself:

Is it possible that the premises are all true and that the claim is true?

Alternatively, ask yourself:

If I believed all the premises, would that lower my degree of belief in the claim?

Exercise 2

Go back over the arguments in exercise 1 and say whether the premises justify the conclusion. For each argument, is it the case that if the premises were true, then the conclusion would be true too? Would believing the premises increase your degree of belief in the conclusion or not?

...

5. Evaluating Arguments using Reason!able

Evaluating truth

1. Switch to evaluation mode
2.'Unfold' the reason or objection
3. Double click on each premise and make an evaluation - definitely false, probably false, no verdict, probably true, definitely true
4. Double click on the question-mark underneath each premise to specify the ground for the premise - common knowledge, expert opinion etc.

Evaluating justification

1. Switch to evaluation mode
2.'Unfold' the reason or objection
3. Double click on the box labelled 'reason' (or 'objection') and make an evaluation - no support/opposition, weak support/opposition, strong support/opposition, conclusive support/opposition.

Exercise 3

Construct an argument map for the following excerpts from Bush's Ethics.

1. First represent the structure of the argument.

Now evaluate the argument. It is a good idea to do this systematically, from the bottom up:

2. Start with the unsupported premises of the argument - the premises which are not based on any supporting reasoning.

3. Now evaluate each reason and objection above each of the unsupported premises.

You are now in a position to evaluate the conclusions of each of the arguments you evaluated at steps 2 and 3. For each such argument, at step 2 you evaluated the truth of all the premises and a step 3 you evaluated the strength of all the reasons and objections to the conclusion, so now you can make a decision about the truth of the conclusion.

4. Evaluate the conclusion of each of the arguments you have covered so far.

5. Repeat steps 3 and 4 for each sub-argument, working your way systematically up to the main conclusion of the argument. The final step will be to make an evaluation of the main conclusion of the argument.

Extract from Lab 5 Tutor's Notes

Exercise 3 Solutions

Excerpt 1

I think this is an argument to the conclusion that religious fervour in the US explains why the separation between church and state is more strictly policed there. Below is my representation and evaluation of the argument. I have put 'testimony' as the ground for any premise that is supposed to be based on evidence from opinion polls (the idea is that, for example, we believe that Americans would not vote for an atheists because they tell us they would not).

map 1

Excerpt 2

1. I have put the ground for the premise 'people who have committed a crime … are not innocent' as 'necessary truth' - taking it to be true by definition of 'innocent' that if you have actually committed a crime, then you are not innocent.
2. I have evaluated the reasoning for the main conclusion as conclusive, but since one of the premises is evaluated 'probably false' and one as 'not evaluated', I have marked the conclusion as 'no verdict'. (And not, as 'probably false' - the fact that the argument fails shows that we can reach no verdict on the conclusion, not that we can infer that it is false).
3. Premises that state the results of studies, I take to be grounded by expert opinion.
4. The premise that fetuses are innocent human beings I have evaluated as 'plausible' - perhaps 'general knowledge' would be equally acceptable here.

map 2

Extracts from Homework Assignment 2

Part I (30 marks)

30 LSAT Logical Reasoning questions on identifying the conclusion of arguments and making correct inferences from given information.

Part II (25 marks)
Paraphrase the excerpts below.

Passage 1
One possible ground for drawing the line between the human and the chimpanzee is that we are human and so we should protect all members of our own species, but we have no duty to protect members of other species. That's a bad answer because it rests on a simple, unargued preference for 'our own'. If we rely on the bare claim that we are human and so should protect our own kind, we have no comeback against racists who maintain that they ought to protect their own kind-by which they mean members of their own race, but not members of other races. (Singer, p. 49)

....

(5 passages from Singer)

Part III (45 total)
Provide a map for each of the following arguments.

Passage 1
Bush, as we have seen, argued that if the embryos are human life, they are precious and to be protected. We can now see what is wrong with this argument. If human life is more precious than non-human life, it is because humans posses higher mental capacities that non-human animals lack. Embryos, however, are utterly lacking in such higher mental capacities. Hence if it is the possession of higher mental capacities that marks the line between beings whose lives need to be protected and beings whose lives do not need to be protected, then human embryos-and fetuses, for that matter-fall on the wrong side of the line. None of them plans ahead, deliberates over choices, or can be held morally responsible. Bush's position requires a morally relevant line of demarcation that human embryos pass. But all Non-human animals fail. The plausible line of demarcation we have been discussing won't do that job. (Singer, p. 51)

Passage 2
Bush's support for the death penalty, in the face of evidence that it is not an effective deterrent, plus the evidence that the American system of justice allows some innocent people to be executed, is not consistent with his professed ethic of respect for innocent human life. Even more glaringly at odds with this ethic are the American military activities he authorised in Afghanistan and Iraq. Bush's concern for the lives of innocent people on death row, and for innocent men women and children in Afghanistan and Iraq falls far short of his concern with protecting embryos that might be used for stem cell research. On any sensible scale, this is a bizarre set of priorities. The frozen embryos that scientists wish to use will be destroyed anyway, if they are not used. They have no future. But even if that were not the case, none of them have, or have had, any conscious awareness, any hopes or desires of their own. No embryos are mothers or fathers., no embryos will leave sorrowing children behind when they are killed. No one keeps photos of dead embryos and grieves over their loss, as Abed Hamoodi grieved, and will continue to grieve as long as he lives, over the deaths of his children and grandchildren.(Singer, p. 70)

Passage 3
But morality does not have to be religious in order to be real and important. We are each of us concerned about our own well-being, or the satisfaction of our wants and desires. When we think ethically, we should do so from an impartial perspective, from which we recognise that our own wants and desires are no more significant than the wants and desires of anyone else. To base judgments about the rights and wrongs of an action on the impact it will have on the welfare of those affected by it is to base ethics on something that is real and tangible. (Singer, p. 130)

  • Undergraduate Studies
  • Postgraduate Studies
  • Research
  • What's Happening