Practically Speaking by J. Dan Rothwell

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Chapter 13 Argument, Reasoning, and Evidence

• An Argument: Staking Your Claim

• Criteria for Reasoning and Evidence

• Credibility, Relevance, and Sufficiency

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Chapter 13 Learning Objectives

• 13.1 Practice constructing an argument that uses sound reasoning and logical evidence.

• 13.2 Distinguish the differences in fact and fallacy to maximize speaker credibility when constructing a given argument.

• 13.3 Determine components of using sufficient proof when constructing a given argument.

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An Argument: Staking Your Claim

An argument ”implicitly or explicitly presents a claim and provides support for that claim with

reasoning and evidence” (Verlinden, 2005, p. 5).

Reasoning is the thought process of drawing conclusions from evidence.

Evidence consists of statistics, testimony of experts and credible sources, and verifiable

facts.

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Why are Reasoning and Evidence Critical?

• Michele Bachmann Speech

• John Oliver takes on opioid addiction

• John Oliver takes on media reporting of bad “science”

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Syllogism: Formal Logic

• Syllogism is the basic structure of an argument

• A syllogism contains three parts:

1. A major premise

2. A minor premise

3. A conclusion

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Toulmin Structure of Argument: Six Elements of an Argument

1. Claim – A generalization that remains to be proven

2. Grounds – Reasons to accept a claim and evidence used to support those reasons

3. Warrant – The reasoning that links the grounds to the claim

4. Backing – The reasons and relevant evidence

5. Rebuttal – Exceptions or refutations that diminish the force of the claim

6. Qualifier – Degree of truth to the claim

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The Toulmin Structure of an Argument

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Identifying Elements of the Toulmin Structure of an Argument (1 of 2)

Choose grounds, claim, warrant, & backing for the following. Create rebuttal and qualifier.

____ Cost of higher education is skyrocketing.

____ Access to higher education is decreasing.

____ Gaining a college degree is important.

____ A college degree opens doors to careers.

____ Public higher education should be free.

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Identifying Elements of the Toulmin Structure of an Argument (2 of 2)

Choose data (grounds), claim, warrant, & backing for the following. Create rebuttal and qualifier.

_G__ Cost of higher education is skyrocketing.

_G__ Access to higher education is decreasing.

_W _ Gaining a college degree is important.

_B__ A college degree opens doors to careers.

_C__ Public higher education should be free.

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Criteria for Reasoning and Evidence: Is it Fact or Fallacy?

• A fallacy is any error in reasoning and evidence that may deceive your audience

• Three criteria for evaluating evidence and reasoning:

1. Credibility

2. Relevance

3. Sufficiency

• Fallacies commonly occur when these criteria are unmet

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Credibility: Should We Believe You?

• Credibility of evidence refers to its believability

as determined by consistency and accuracy

• Be mindful of:

– Manufactured or questionable statistics

– Biased sources

– Expert quoted out of the field

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Questionable Statistics

• The number of text messages in America

• Weird and wild statistics

• One questionable statistic

• “Researchers say they’ve figured out why people

reject science, and it’s not ignorance”

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Relevance: Does it Follow?

• A common type of fallacy is non sequitur,

meaning “it does not follow”

• Two common non sequiturs:

1. Ad hominem

2. Ad populum

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Ad Hominem Fallacy: Diversionary Tactic

• The ad hominem fallacy is a personal attack on

the messenger to avoid the message

• Examples of the ad hominem fallacy:

–Marco Rubio Attacks Trump

– Trump attacked Nancy Pelosi, who attacked him

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Ad Populum Fallacy: Arguing from Public Opinion

The ad populum

fallacy is when views

are based primarily on

popular opinion (even

if it contradicts

scientific evidence)

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Sufficiency: Got Enough?

Several fallacies exhibit insufficiency that involve:

• Self-selected samples

• Inadequate samples with large margins of error

• Hasty generalizations

• Correlation mistaken for causation

• False analogies

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Self-Selected Samples

• A random sample is a portion of the target population chosen so that every member has an equal chance of being selected

• Self-selected sample attracts the most committed or motivated individuals to fill out surveys on their own

• Example of self-selected sample results versus random sample results

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Inadequate Sample: Large Margin of Error

• A single study proves very little

• One study is insufficient to draw general conclusions

• The margin of error is a measure of the degree of sampling error accounted for by imperfections in a sample selection

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Hasty Generalizations: Arguing from Example

• Individuals make hasty generalizations when they jump to conclusions based on a single or handful of examples

• The vividness effect fallacy is when vivid images skew perceptions of what to believe is true

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Inductive vs. Deductive Reasoning (1 of 2)

Induction: Reasoning from specific observations or instances to a generalization/conclusion

Deduction: The process of reasoning from general premises to a certain conclusion

Do syllogisms use inductive or deductive reasoning?

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Example: Sherlock Holmes

This is Sherlock Holmes in action Analyzing Watson’s girlfriend

Showing off to a client

Does he use inductive or deductive reasoning?

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Inductive vs. Deductive Reasoning (2 of 2)

Sherlock Holmes was wrong!

He did not use primarily deductive reasoning.

He used primarily inductive reasoning.

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Deductive Reasoning as a Syllogism

Major Premise: All humorous teachers are great teachers.

Minor Premise: Professor Hilarious Parody is a humorous teacher.

Conclusion: Professor Hilarious Parody is a great teacher.

This is a “valid” argument (its conclusion follows logically from its premises). It is not a “sound”

argument, however–its premises are not all true. Why?

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Correlation Mistaken for Causation: X Does Not Necessarily Cause Y

• Causal reasoning occurs when we see events and infer what caused these events

• A correlation is a consistent relationship between two variables

• Correlations suggest possible causation

• Even a perfect correlation does not mean there is causation

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False Analogy: Mixing Apples and Oranges • Analogical reasoning alleges that because

two things closely resemble each other, both should logically be viewed in similar ways – John Oliver Employs Analogical Reasoning

• Comparing politicians to Hitler: – Obama as Hitler

– Bush as Hitler

– Hillary Clinton as Hitler

– Donald Trump as Hitler

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Review of Chapter 13 Learning Objectives

• 13.1 Practice constructing an argument that uses sound reasoning and logical evidence.

• 13.2 Distinguish the differences in fact and fallacy to maximize speaker credibility when constructing a given argument.

• 13.3 Determine components of using sufficient proof when constructing a given argument.