Solutions for Exam: Deductive Arguments

Thank you for undertaking the Exam on Deductive Arguments. We hope you found it stimulating. Here are your solutions.

Which of these statements is true?

“A deductive argument leads to a conclusion which is absolute, or certain.”  This statement is true.
In fact, some of our clients map their ideas out deductively to check whether their logic stacks up before they decide how to communicate to their audience. Quite often they find that they communicate inductively but with more confidence knowing that their logic is robust having mapped the story out deductively as a test.

How many ideas should you have at the key line in a deductive argument?

Three ideas and only three. Longer deductive chains are useful in problem solving – they can be as long as you like when used for this purpose. However, long deductive chains are awfully hard for a reader to follow, as they require the reader to absorb a lot of information before they get to the big idea. They are also logically risky as there are more links that might break. Therefore, we recommend sticking to only three key-line ideas within a deductive storyline.

Deductive arguments are powerful when the logic is tight, but otherwise risky. Why?

All of these points are correct: 

The conclusion at the right side of your deductive chain must only be supported by …

Actions. By the time you are revealing your conclusion to your audience, you will have already persuaded them that it is right and they will be ready to hear how you plan to implement it. You should not need further reasons at this stage. If you still need to persuade at this point, you need to revisit your logic.

Which deductive chain works?

“Deductions are only given when receipts are provided, you have not provided receipts, therefore you are not entitled to a deduction.”
This chain works because it is logically tight. There are flaws – sometimes small ones – in the chains below, which I have highlighted.
Flawed chain 1:Deductions are only given when receipts are provided, you have receipts, therefore you are entitled to a deduction. (Just because you have receipts, does not mean you have provided them.)”
Flawed chain 2: Deductions are given to legal entities that provide genuine receipts, you have provided genuine receipts, therefore you are entitled to a deduction. (Just because you have provided genuine receipts does not mean that you are a legal entity.)

A deductive storyline must contain 3 parts

True. A deductive storyline has three components to the logic that supports the governing thought. These are:

  1. A major premise which is an irrefutable fact but still “news” to the audience
  2. A comment on the major premise, which logicians refer to as a “minor premise”. This is often the “however” point. The major premise and minor premise must be linked in such a way as to lead to one and only one implication
  3. An implication of the major premise and minor premise which is often described as the “therefore” point, or conclusion.
  4. There are many variations on deductive storylines but they must follow that basic order. Every deductive storyline is of course the logical support for a governing idea.

Groupings of ideas support each premise within a deductive argument

True. The support for each part of the deductive storyline will be arranged as a grouping. Usually it means a grouping of reasons that support the major premise (although sometimes they may be examples), a grouping of reasons to support the minor premise (or examples) and then a grouping of actions to support the recommendation (or conclusion).

The Governing Idea should be EXACTLY the same as the Conclusion, or “Therefore” point

False. The Governing Idea should be the synthesis of the whole story, which means that it must synthesise both the reasons why your conclusion is valid, and the conclusion itself. For example, not just “Take steps to fix X” but “ABC should take steps to fix X to turn around poor performance”

A deductive argument flows from …

The general to the particular.

You must never use a deductive storyline with a resistant audience

False. Sometimes a deductive storyline can be used very effectively with a resistant audience to demonstrate that there is no other course of action than the one you are suggesting. However, you do need to be very careful that you have the necessary evidence to support your deductive storyline. So, double-check your facts and ensure that the major premise and minor premise are linked in such a way that they lead unquestionably to the conclusion.

The “Therefore” section can contain “why” support

False. The conclusion must NEVER be supported by reasons – it should always be supported by actions. If you feel it needs to be supported by reasons then that means your argument is not sound.

In what situation would you use a four-point deductive argument?

  1. When you do have two comments, one that comments on the other
  2. When you have an extra high level point that is separate enough but dependent upon the other points to be included in the key line
  3. When you really do have two statements that are dependent up on each other

Any of the above

What happens when you stack a deductive argument directly on top of another deductive argument?

  1. The governing idea is only as strong as the lowest level points
  2. The governing idea is only as strong as the connections between the lowest level points
  3. It is horrid for your reader to work through

All of the above are true

What is the combined purpose of the statement and the comment?

The statement and the comment together persuade your audience that your conclusion is the only possible correct conclusion.

What is the ultimate test for the veracity of a deductive argument?

That the conclusion must be true, or in other words, that it cannot be false.

When evaluating a deductive argument, we must consider…

Number three is correct: both form and fact stack up.

  1. That the content makes sense
  2. That the logical form stacks up
  3. That both the form (structure) and the content stack up

Why should you avoid recommending people use four-point deductive arguments?

  1. The more links between ideas, the more chance the chain will break
  2. The more links between ideas, the more confused the audience may become
  3. It is very rare to really need to use four points to get your point across

All of the above are correct

The answer (or governing idea) that overarches a deductive story must include

Your recommendation AND the reasons supporting it. A deductive argument includes both your recommendation and the reasons for it and the answer must synthesise the whole argument, which means that the must speak to both of these things.

How do you decide whether to choose to present your ideas deductively or not?

  • Your audience needs to know why something should be done
  • Your audience needs to know how something should be done
  • Your audience needs to know both how and why something should be done

The third point is more correct than the other two: numbers one and two are also correct, but the audience wants to know both why and how something should be done.

What is wrong with this deductive argument?

Statement: Mary is on the swim squad
Comment: The swim squad is exempt from regular school sport
Conclusion: Therefore, Mary is exempt from regular school sport *

  1. It is a deductive argument with only three parts
  2. The argument does not flow from the general to the particular
  3. The comment does not truly comment on the statement

Number two is correct. It would be better to order it this way: The swim squad is exempt from regular school sport and Mary is on the swim squad. Therefore, Mary is exempt from regular school sport.

What is wrong with this deductive argument?

Governing idea: Like all firefighters, Maude must renew her first aid certificate annually
Statement: Maude is a firefighter
Comment: Firefighters must renew their first aid certificates annually
Conclusion: Therefore, Maude must renew her first aid certificate

  1. The argument does not flow from the general to the particular
  2. The conclusion is not specific enough
  3. The comment does not truly comment on the statement
  4. All of the above

All of the above: the argument does not flow from the general to the particular, the conclusion is not specific enough and the comment does not truly comment on the statement.

What is wrong with this deductive argument?

Governing idea: Like all firefighters, Maude loves swimming

Statement: Maude loves swimming
Comment: Maude is a firefighter
Conclusion: Therefore, all firefighters swim

  1. The argument does not flow from the general to the particular
  2. The comment does not truly comment on the statement
  3. The two ideas above are correct
  4. The conclusion is not specific enough

Solution: The correct answer is 3: The two ideas above are correct. This is because the argument does not flow from the general to the particular and the comment does not truly comment on the statement.

The first two are correct, which means that the third option is the correct answer. The argument does not flow from the general to the particular: Maude loves swimming and Maude is a firefighter are two ideas that are the same kinds of things: they are descriptions of Maude. In light of that, it is also true that the comment does not comment on the statement: They are separate ideas and not connected to each other.
The conclusion is specific enough in the circumstances which means that point three is not true

What is wrong with this deductive argument?

Statement: OilyCo's profits are falling in line with the oil price
Comment: The legislative environment in the US is getting tougher for corporates
Conclusion: OilyCo should sell its PNG oil and gas interests

  1. The comment does not truly comment on the statement
  2. The argument does not flow from the general to the particular
  3. The conclusion does not flow from the comment or the statement
  4. All of the above

All of the above is the correct answer.

  • The comment does not comment on the statement: The idea that OilyCo's profits are falling in line with the oil price has nothing to do with a tough legislative environment in the US
  • The argument does not flow from the general to the particular: To start the argument with a point about OilyCo's profits and then lead to a comment about the legislative environment is working from the specific to the general, not the other way around
  • The conclusion is not related to either the statement or the comment

What is wrong with this deductive argument?

Statement: OilyCo has extensive interests in PNG oil and gas fields
Comment: The oil price is declining, and PNG is a risky operating environment politically
Conclusion: Oil and gas is a tough business to be in

  1. The comment does not truly comment on the statement
  2. The argument does not flow from the general to the particular
  3. The conclusion does not flow logically from the combination of the statement and the comment
  4. All of the above

All of the above is correct.