Chapter Fourteen: Reasoning
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Chapter Goals
Chapter 14 addresses the importance of sound reasoning in speeches when entering the public dialogue.
Students should have an understanding of the following goals after the end of this chapter:
• To identify and apply Aristotle’s three modes of proof
Chapter Outline
a. Sound reasoning plays a central role in your preparations to enter the public dialogue.
(pg. 267-268)
b. Speakers accomplish sound reasoning when they use the three forms of proof defined by
the Greek philosopher Aristotle.
i. Logos refers to the logical arrangement of evidence in a speech.
ii. Ethos refers to the speaker’s credibility.
I. Patterns of reasoning. (pg. 268)
a. Induction, or Reasoning from Specific Instances.
i. Inductive reasoning is a process of reasoning that uses specific instances, or
examples, to make a claim about a general conclusion Figure 14.1, pg. 269.
1. Inductive reasoning is sometimes called argument by example.
2. Best used when you can identify patterns of evidence which indicate
3. You can use inductive reasoning in two ways.
a. State your claim (general observation) first and then offer
ii. Guidelines for using inductive reasoning. (pg. 270)
1. Make sure you have enough examples to make your claim.
2. Make sure your generalizations are accurate.
b. Deduction, or reasoning from a general principle. (pg. 270)
i. Deductive reasoning is a process of reasoning that uses a familiar and
commonly accepted claim to establish the truth of a very specific claim.
v. Guidelines for deductive reasoning.
2. When audiences do not accept your general principle easily, then
3. In order for your audience to accept your conclusion, they need to accept
your major premise.
c. Causal reasoning is a process of reasoning that supports a claim by establishing a
cause-effect relationship. (pg. 272)
i. Causal reasoning identifies an “if–then” relationship meaning “if” a certain factor
is present, “then” something else is sure to happen.
ii. Guidelines for causal reasoning.
1. Avoid false causes, or an error in reasoning in which a speaker assumes
d. Analogical reasoning is a process of reasoning by way of comparison and similarity that
implies that because two things resemble each other in one respect, they also share
similarities in another respect. (pg. 273)
i. Reasoning analogically also exists when we compare differences in two similar
1. Be sure that your analogies are valid.
Compare two things that share characteristics.
e. Reasoning by sign. Process of reasoning that assumes something exists or will happen
based on something else that exists or has happened.
i. Sign, Something that represents something else. (pg. 274)
2. Reasoning by sign helps speakers establish relationships and draw
conclusions for their audiences based on those relationships.
ii. Guidelines for reasoning by sign. (pg. 274)
1. Think about whether an alternative explanation is more credible.
II. Tips for reasoning ethically. (pg. 275)
a. Build your credibility.
i. Credibility is the audience’s perception of a speaker’s competence and
character.
ii. Competence is the audience’s view of a speaker’s intelligence, expertise, and
knowledge of a subject.
iii. Character is the audience’s view of a speaker’s sincerity, trustworthiness, and
concern for the well-being of the audience.
1. When you reason ethically, you convey to the audience that you have
b. Use accurate evidence. (pg. 276)
i. Although it often is easy to find supporting materials, those materials may be
incorrect.
c. Verify the structure of your reasoning.
The Toulmin map of reasoning is the final way to ensure the ethical nature of reasoning.
i. Using this model, you can check the claims, warrants, grounds, and backing for
any claim to ensure the ethical nature of those claims.
ii. When you identify weaknesses and potentially disturbing claims before
presenting them to your audience, you are acting ethically.
III. Fallacies in reasoning. (pg. 276) Table 14.1, Additional fallacies often heard in speeches, pg. 282
A fallacy is an argument that seems valid but is flawed because of unsound evidence or reasoning.
There are over 125 different fallacies, but this chapter focuses on the seven most common types.
a. Ad hominem fallacy is an argument where the speaker attacks the person rather
than the person’s argument. (pg. 277)
b. Bandwagon fallacy is an argument that suggests something has merit because
everyone else agrees with it or is doing it. (pgs. 277-278)
g. Slippery slope fallacy is an argument that claims a first step in a certain direction
will inevitably lead to undesirable further steps in that direction. (pg. 281)
h. Staying audience centered. With so many kinds of reasoning, you must work to
stay audience centered. (pg. 282-283)
i. Make sure the reasoning is audience centered.
End of Chapter Activities and Discussion Questions
The following questions can be found at the end of Chapter 14.
Review Questions and Activities
1. Bring a copy of the newspaper to class. In groups, identify as many different types of reasoning as you
can find in the text, photographs, or advertisements. Label each item you find inductive, deductive,
causal, analogical, or sign, and evaluate the strength of each item’s reasoning according to the
guidelines discussed in this chapter.
At the end of this chapter, you will find a handout with the guidelines for each type of reasoning. Provide
2. This chapter suggests that a speaker’s credibility is an important part of the ethical process of using
reasoning. Do you agree? Why or why not? Can you identify speakers you have heard or read about
who do not have much credibility and you would deem unethical? Compare those speakers lacking
credibility to a speaker you find credible. Whose arguments do you find more ethical?
This is a great question to address when lecturing about credibility because students will view speakers’
credibility quite differently. For instance, students may talk about credibility and appearance. Some
3. Bring a copy of the morning newspaper or your favorite magazine to class. In groups, identify as many
different types of fallacies as you can find. Now that you recognize these fallacies, evaluate the strength
of the argument being advanced.
Web Activities
1. Aristotle’s Forms of Proof
Purpose: To learn how to distinguish among ethos, pathos, and logos.
page through a magazine and find examples of each form. Which form most persuades you? Which
form was most common in the magazine you read? Why do you think that is?
2. Green Belt Movement
movement. As well, if you are interested in doing volunteer work in Kenya, the information provided
through this resource can be very helpful.
Interactive Student and Professional Speech Videos in MindTap
Video Clip 1: Colt “Implications of Social Networking and Text Messaging”
1. As you watch Colt use deductive reasoning, consider the tests of deduction discussed in this chapter.
How does Colt establish the validity of his major premise? Do you accept his premise? Why or why
not?
Show this video clip in class as an example of deductive reasoning. Have students respond to the
Additional Exercises and Resources
1. Assessing Inductive Reasoning
Purpose: To evaluate inductive arguments critically.
Directions: Go to the Arguments by Example web page at
then look through a current newspaper, paying particular attention to persuasive articles or
advertisements. Locate examples of inductive reasoning. Which of these examples is valid? Which
should you question?
2. Identifying Different Types of Reasoning
As a homework assignment, have students begin by listing and defining each type of reasoning. Then,
have students provide an example for each (other than what is found in Chapter 14 of Invitation to
Public Speaking). Examples can come from newspapers, magazines, conversations with friends, or
examples they create. On the due date of the assignment, place students into groups of 3-4. Assign each
3. Using the Different Types of Reasoning
This is a variation of activity #1 appearing in the general activities section of this chapter. Have students
bring in newspapers. Place student into groups of 3-4 and assign each group one or two types of
4. Identifying Fallacies
As a homework assignment, have students list and define each of the fallacies defined in this chapter
(hasty generalization, false cause, invalid analogy, etc.). Students should then provide an example of
each, other than what appears here in the textbook. You can ask each group to present the fallacious
Reasoning Effectively
A Checklist
As you work on in-class assignments, and your own speeches, be sure to use sound reasoning. This handout
has the definitions for each type of reasoning, along with an example to help you review. Use the checklists
as a guide to verify your own reasoning.
1. Inductive reasoning: A process of reasoning that uses specific instances, or examples, to make a
claim about a general conclusion.
Example: “Animals in six slaughterhouses I researched experience harsh conditions and
unnecessary cruelty. Animals in slaughterhouses throughout the United States are treated
inhumanely and I decided not to support this treatment by not eating them.”
_____ Have you stated your claim clearly?
2. Deductive reasoning: A process of reasoning that uses a familiar and commonly accepted claim
to establish the truth of a very specific claim.
Example: “Grade inflation negatively affects all college students. Jody is a college student. Jody
is affected negatively by grade inflation.”
_____ Have you clearly stated your general premise?
3. Causal reasoning: A process of reasoning that supports a claim by establishing a cause-effect
relationship.
Example: “Zebra mussels cause damage to every aspect of any aquatic ecosystem they encounter.
They destroy the natural balance of the ecosystem by filtering the food from water at an insane rate
of one liter of water each day. These mollusks can live in colonies of up to 70,000 mussels. That’s
70,000 liters of water cleared of all food each day. Zebra mussels consume all the food usually
eaten by animals lower in the food chain. The result is catastrophic repercussions on down the line.
. . .”
_____ Have you clearly identified an “if–then” relationship?
_____ Have you avoided the fallacy of false cause?
_____ Can the specified event have more than one cause?
_____ Have you cited enough supporting evidence to convince your audience?
4. Analogical reasoning: Reasoning suggesting that because two conditions or events resemble each
other in ways that are certain, they will resemble each other in other ways that are less certain.
Example: “It’s like paying for your groceries and then leaving them at the store! If students want
to pay tuition and then not show up for class or do the work, I guess that’s their right.”
_____ Are the cases you are comparing truly alike?
_____ Have you avoided invalid analogies?
_____ Is the analogy clear?
5. Reasoning by sign: Using the appearance of one thing to signal the likely appearance of another
thing.
Example: “The silence from upper management is a sign that it’s about to make changes.”
_____ Is there an alternative explanation that is more credible?
_____ Is the sign an isolated case?
_____ Can you find instances in which the sign DOES NOT indicate the event?
Avoiding Fallacies
As you work on in-class assignments and your own speeches, be sure to avoid fallacies. This handout has
the definitions for each type of fallacy identified in this chapter. Use the checklists as a guide to check your
own reasoning.
1. Hasty generalization: Reaching a conclusion without enough evidence to support it.
_____ Are your generalizations accurate?
_____ Do you have enough evidence to support your generalization?
2. False cause: An error in reasoning in which a speaker assumes that one event caused another
simply because the first event happened before the second.
_____ Does the event have more than one cause?
_____ Do you have enough evidence to support your claim?
3. Invalid analogy: Comparing two conditions or events that do not share characteristics.
_____ Are the cases being compared truly alike?
_____ Do the conditions being compared have common characteristics?
Supplemental Bibliography
Allen, James. Inference from Signs: Ancient Debates About the Nature of Evidence. New York: Oxford
University Press, 2001.
Offers a historical perspective on reasoning and argument forms.
Heit reviews the psychological process involved in inductive reasoning based on the last 25 years
of research and provides instructors with a deeper understanding of induction. A nice resource for
lecture material and examples.
Langford, Peter E., and Hunting, Robert. “A Representational Communication Approach to the
Development of Inductive and Deductive Logic.” Advances in Psychology 106 (1994): 191-212.