Reasoning by Analogy

What is an analogy? http://www.youtube.com/watch?v=YiorwR

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Definition of Analogy 5. Logic. a form of reasoning in which one

thing is inferred to be similar to another thing in a certain respect, on the basis of the known similarity between the things in other respects.

Toulmin’s Model and Analogies Data is the support

of an argument, and the warrant is the reasoning that leads to the claim.

Analogies are used in the reasoning step, as warrants.

Correct Usage of Reasoning by Analogy Bob has a car (he also has aqua colored

hair).

(cont.) His twin brother Joe has a car that is the

same model and year. It is reasonable to assume, in this situation

that both cars are worth about the same amount of money.

Incorrect Usage of Reasoning by Analogy Since both brothers’ cars are the same

model and year, it is reasonable to assume they are also the same color.

Right?

Although both brothers do have aqua hair.

Positives Reasoning by analogy is effective when

used correctly, because it makes sense to most people that when two situations are similar, the outcomes should also be similar.

For Example… Product X uses a testimonial

advertisement. Julia says, “When I used Product X, it made my acne go away.” Therefore, because Product X worked for Julia, it should also work for Janie, her sister, who has similar skin problems.

Negatives Analogies often fall flat because in order

for them to work, the two cases involved must be similar in all major respects. Minor differences might not affect the final conclusion. However, there are too many variables to be accounted for that might possibly effect the outcome.

For Example… Janie buys Product X on her sister’s

suggestion. However, Product X only makes her acne worse because she has more sensitive skin.

Quiz…Over TWO Powerpoints Analogies are used in the _______ part of

the Toulmin model. What is the difference between figurative

and literal analogies? In order for analogies to work, the two

cases involved must be (similar/different) in all major respects.

Conclusion Analogies can be a persuasive technique in

argumentation and debate, but it is best to make sure that the analogies are valid and foolproof.