Critical Thinking:A User’s Manual

Chapter 9Evaluating Analogical Arguments

Analogical Arguments

An analogical argument is an inductive argument that uses an analogy to show that because one case has a particular feature, the other case should, too.

An analogy is a claim that compares two , or more, things.

Analogies

Learning is like rowing upstream.My love is like a red, red rose.Life is a rollercoaster.

Cats are like dogs. Since dogs make good pets, cats probably make good pets.

P1: P2:

Issue:

Cats are like dogs. Since dogs make good pets, cats probably make good pets.

Anatomy of Analogical Arguments

P1: (analogy) T is like SP2: (feature) S has F T has F

S = sampleT = targetF = feature

Cats are like dogs. Since dogs make good pets, cats probably make good pets.

P1: P2:

S: T: F:

Both Brenda and Susan live in Orange County, have three children in private schools, and drive BMWs. Since Brenda is wealthy, Susan probably is, too.

P1: P2:P3:

P1: P2:

Issue:

Both Brenda and Susan live in Orange County, have three children in private schools, and drive BMWs. Since Brenda is wealthy, Susan probably is, too.

S: T: F:

Both Brenda and Susan live in Orange County, have three children in private schools, and drive BMWs. Since Brenda is wealthy, Susan probably is, too.

Evaluating Analogical Arguments

Analogical arguments may be strong or weak.Consider evidence for the analogyConsider relevance of the analogy

Evaluating Evidence for the Analogy

Sample sizeThe more instances in the sample, the stronger

the argument.Quantity of similarities

The more relevant characteristics shared by the sample and target, the stronger the argument.

Which argument is stronger?

Brenda and Susan live in Orange County. Since Brenda is wealthy, Susan probably is, too.

Carla, Mary, Brenda, and Susan all live in Orange County. Since Carla, Mary, and Brenda are wealthy, Susan probably is, too.

Which argument is stronger?

Both Brenda and Susan live in Orange County, have three children in private schools, and drive BMWs. Since Brenda is wealthy, Susan probably is, too.

Both Brenda and Susan live in Orange County. Since Brenda is wealthy, Susan probably is, too.

Evaluating Relevance of the Analogy

An analogical argument uses a faulty analogy whenever the similarities between the sample and target are irrelevant to the feature.

Is the analogy relevant?

Brenda and Susan have three children. Since Brenda is wealthy, Susan probably is, too.

Complete Analysis plus Evaluation

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

Step 2: If it is an argument, determine whether it commits a fallacy. Identify the fallacy, and explain how it is committed.

Step 3: If it is a nonfallacious argument, diagram it.Verify that your diagram is consistent with your Basic

Analysis.

Complete Analysis plus Evaluation

Step 4: Identify the kind of argument. If the argument is deductive, identify it as a categorical

argument or a truth-functional argument. If the argument is inductive, identify it as an analogical

argument, an inductive generalization, or a causal argument.

Complete Analysis plus Evaluation

Step 5: Evaluate the argument. If the argument is categorical, state the syllogism in

standard form, and demonstrate whether the argument is valid or invalid using either a Venn diagram or the rules for valid syllogisms.

If the argument is truth-functional, translate the argument, and demonstrate whether the argument is valid or invalid by identifying the argument form, using the truth table method, or using the shortcut method.

If the argument is analogical, evaluate its strength by considering the evidence provided for the analogy and the relevance of the analogy to the feature.

An "online affair" is just like an affair in person because they both devalue their primary partners. Since divorce is the appropriate response to an affair in person, it is also an appropriate response to an online affair.

This passage contains an argument. The issue is whether divorce is an appropriate response to an online affair. The conclusion is that divorce is an appropriate response to an online affair. The first premise is that an online affair is like an affair in person. The second premise is that divorce is an appropriate response to an affair in person.

This passage contains a subargument. The intermediate conclusion is that an online affair is like an affair in person. The premise is that both online affairs and affairs in person devalue their partners.

An "online affair" is just like an affair in person because they both devalue their primary partners. Since divorce is the appropriate response to an affair in person, it is also an appropriate response to an online affair.

+

This passage contains an argument. The issue is whether divorce is an appropriate response to an online affair. The conclusion is that divorce is an appropriate response to an online affair. The first premise is that an online affair is like an affair in person. The second premise is that divorce is an appropriate response to an affair in person.

This passage contains a subargument. The intermediate conclusion is that an online affair is like an affair in person. The premise is that both online affairs and affairs in person devalue their partners.

This passage is an inductive analogical argument. The argument is somewhat strong because the analogy is relevant to the feature, but there is only one similarity to support the analogy and only one instance in the sample.