Critical Thinking: A User ’ s Manual

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Critical Thinking:A User’s Manual

Chapter 4Diagramming Arguments

Argument Diagram

An argument diagram is a visual representation of the structure of an argument.

An argument diagram shows the relationship between the premises.

Relationships between Premises

Convergent premises provide support for the conclusion independently of one another.If one premise is removed, the conclusion may

still be supported by the other(s).Linked premises depend on each other to

provide support for the conclusion.If one premise is removed, the conclusion is no

longer supported.

How to Diagram Arguments

Step 1: Underline and number each claim.Step 2: Pay attention to indicator words.Step 3: Identify the main conclusion.Step 4: Identify the premises and determine

their relationship.Step 5: Diagram any subarguments.Step 6: Check your work.

Numbering Claims

Underline every claim.Give each claim its own number.If a claim is repeated, use the same number.If a conclusion is unstated, write the

conclusion after the passage and give it a number.

If a claim is implied, underline and number the non-claim serving as a placeholder and write the implied claim after the passage.

Using Inference Indicators

Rewrite the argument by substituting numbers for each claim.

Use the inference indicators to draw a preliminary diagram of the argument.

Remember that “and” cannot tell you whether the premises are linked or convergent.

Drawing Your Diagram

Place the conclusion at the bottom of your diagram.

Place the premises above the conclusionDraw an arrow from each convergent premise

to the conclusion.Connect each linked premise with a “+”,

underline all linked premises, and draw a single arrow to the conclusion.

Checking Your Work

Read the argument back to yourself to listen for errors.

“+” means “and”Substitute an inference indicator for “”

“____ because ____” when reading the argument from the bottom up

“____ therefore ____” when reading the argument from the top down

Grace is armed, so she’s dangerous.

, so .

Here are some reasons why you should stop smoking cigarettes: smoking is addictive, and it is bad for your health.

Here are some reasons why : , and .

Here are some reasons why you should stop smoking cigarettes: smoking is addictive, and it is bad for your health.

You are pregnant, and smoking while pregnant could hurt the fetus. Therefore, you should stop smoking cigarettes.

and . Therefore .

You are pregnant, and smoking while pregnant could hurt the fetus. Therefore, you should stop smoking cigarettes.

Felipe ought to try out for wrestling, since he is both strong and quick. That’s what I would do if I were him.

, since . .

Smoking is not allowed in this restaurant. I know this is true because I was told to put my cigarette out the last time I was here.

Anyone guilty of leaking classified government documents is guilty of treason, and that is just what Julian Assange has done.

Anyone guilty of leaking classified government documents is guilty of treason, and that is just what Julian Assange has done. Julian Assange is guilty of treason.

You should bring your lunch to work. Doesn’t it save you money?

You should bring your lunch to work. Doesn’t it save you money? Bringing your lunch to work will save you money.

Diagramming Multiple Arguments

Arguments with multiple conclusions and chain arguments can be represented in a single diagram.

Pay close attention to inference indicators.

The Saints are likely to retain all of their best starters from last year’s championship team. Thus, Reggie Bush will be their premier running back, and Drew Brees will be their quarterback this year.

. Thus, and .

The Saints are likely to retain all of their best starters from last year’s championship team. Thus, Reggie Bush will be their premier running back, and Drew Brees will be their quarterback this year.

Since Reggie Bush was injured last week, he won’t be able to play in the next game. This means that Chris Ivory will be the Saints’ starting running back.

Since , . This mean that, .

Since Reggie Bush was injured in the last week, he won’t be able to play in the next game. This means that Chris Ivory will be the Saints’ starting running back.

Your turn!

What is wrong with the following diagram?

Extended Arguments

Extended arguments contain several subarguments.

Break down the passage into small, manageable parts.

Pay close attention to inference indicators.

The Galaxy Corporation wants to build a casino in St. Louis, but we should not allow it to be built. First, gambling is immoral, since gambling is motivated by greed, and greed is an immoral desire. Second, communities with casinos have higher crime rates. This is because casinos attract people who take risks, and risk-takers are more likely to break the law. Finally, studies show that people living within 10 miles of a casino have a 90% increased risk of becoming pathological gamblers. Thus, casinos encourage psychological problems for the people that live near them. For all these reasons, the proposed casino should be opposed.

, but . First, , since , and . Second, . This is because , and . Finally, . Thus, . For all these reasons, .

First, , since , and .

Second, . This is because , and .

Finally, . Thus, .

For all these reasons, .

First, gambling is immoral, since gambling is motivated by greed, and greed is an immoral desire.

Second, communities with casinos have higher crime rates. This is because casinos attract people who take risks, and risk-takers are more likely to break the law.

Finally, studies show that people living within 10 miles of a casino have a 90% increased risk of becoming pathological gamblers. Thus, casinos encourage psychological problems for the people that live near them.

For all these reasons, the proposed casino should be opposed.

The Galaxy Corporation wants to build a casino in St. Louis.

Gambling is immoral. Communities with casinos have higher crime

rates. Casinos encourage psychological problems for

the people that live near them.

the proposed casino should be opposed.

The Galaxy Corporation wants to build a casino in St. Louis, but we should not allow it to be built. First, gambling is immoral, since gambling is motivated by greed, and greed is an immoral desire. Second, communities with casinos have higher crime rates. This is because casinos attract people who take risks, and risk-takers are more likely to break the law. Finally, studies show that people living within 10 miles of a casino have a 90% increased risk of becoming pathological gamblers. Thus, casinos encourage psychological problems for the people that live near them. For all these reasons, the proposed casino should be opposed.

Basic Analysis with Argument Diagram

Step 1: Write a Basic Analysis of the passage.Identify the passage.Analyze the passage.

Step 2: If it is an argument, diagram it.Verify that your diagram is consistent with your

Basic Analysis.

Since Reggie Bush was injured last week, he won’t be able to play in the next game. This means that Chris Ivory will be the Saints’s starting running back.

This passage contains an argument. The issue is whether Chris Ivory will be the Saints’ starting running back. The conclusion is that Chris Ivory will be the Saints’ starting running back. The premise is that Reggie Bush won’t be able to play in the next game.

This passage contains a subargument. The intermediate conclusion is that Reggie Bush won’t be able to play in the next game. The premise is that Reggie Bush was injured last week.

Critical Thinking: A User ’ s Manual

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