Evaluating Persuasive Arguments Mary Barrett

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Evaluating Persuasive Arguments

©Mary Barrett


Mayo High School

1420 SE 11th Avenue

Rochester, MN 55904

Critical Reading Lessons

Understanding Logic and Errors in Logic

Many common errors in logic (fallacies) are misuses of induction or deduction.

INDUCTION: Inductive reasoning, or induction, draws general conclusions from particular examples or evidence.
Ex. Because the plums were in the refrigerator when I left, and because George was the only person left in the house, and because the plums have disappeared, and because there are plum pits in the sink, I conclude that George ate the plums.

DEDUCTION: Deductive reasoning, or deduction, applies to a general truth to a specific instance. We deduce by three-step thinking called the syllogism.

Premise 1 Premise 2 Conclusion

All birds have wings. My parakeet is a bird. My parakeet has wings.

All people are mortal. I am a person. I am mortal.

Critical Reading

Quick Analysis Chart

If the premises are:

And the argument is:

Then the proposition is:













PREMISE – assumption
ARGUMENT – statements that follow from and provide truth/evidence/support for the proposition

The conclusion of an argument is that statement which is proved by statements in the argument. These other statements which are offered as reasons for accepting the conclusion are the premises of the argument. The premises and the conclusion constitute the structure of an argument.

Below are two examples of deductive arguments. In each case (P) indicates that the statement which follows is a premise, and (C) indicates that the statement that follows is a conclusion.
1. (P) Any student who received an “A” on her position paper demonstrated that she constructed a superior paper. (P) Since Agnes earned an “A”, (C) Agnes demonstrated that she had written a superior paper.
2. (P) Anyone who is enrolled in Great Decisions is an intelligent person. (P) Laurence is enrolled in Great Decisions, therefore,(C) Laurence is intelligent.
In order to have an argument at all, some statement must be marked out as a conclusion and some other statements must be marked out as premises for that conclusion. Where premises are offered as supporting evidence or justification of the conclusion, two questions arise.
1. Are the premises related properly to the conclusion? (This point refers to the form of the argument.) If the premises are related to the conclusion the argument is valid. If not, the argument is invalid.
2. Are the premises true? (This part refers to the truth or falsity of the premises of the argument.) If the premises are false, the argument is unsound; if the premises are true and the argument is valid, the argument is sound.
To be acceptable, an argument must be valid, and the premises must be true. If the argument is valid and the premise are true, you have employed sound logic. (Note: Just because all the premises are true and the conclusion is true, it does not automatically follow that the argument is valid.)

Evaluating a Persuasive Argument
Writing that contains a persuasive argument has the following components:


Supporting Facts/Development of Argument

Opposing Viewpoint


Call to action (optional)


This is the author’s main point (similar to a main idea or thesis statement). During the argument, the author is going to try to convince you to believe his premise. The premise should be stated clearly and simply near the beginning of the author’s writing. While the premise will be similar to the conclusion, they are not usually exactly the same.


The author must give you the reasons (rationale) that he believes his premise, supported by documented facts that are both credible and either documented or verifiable.

Support Facts/Development of Argument

Generally, an author will divide his main argument into sub-points. For each sub-point, the author will write a topic sentence (or thesis statements in longer works). After the author has stated the main idea, he needs to give elaboration on that idea. In other words, the author must give EVIDENCE, and the reader needs to evaluate the evidence.

  • Is the evidence documented?

In other words, do you know where the information came from?

  • Is the source of the information reliable?

Is the source of the information known to be fair and unbiased?

Is the information from this source similar to information in other sources?

Does the author have a balance of sources such as newspapers, personal interviews, magazines, professional journals, the Internet, etc.?

Does the author rely overly much on one source?

  • Is the information current?

The fact that information is only 2-3 years old isn’t always enough. Has anyone had a breakthrough on this topic (especially in science, medicine, technology) that has changed the way experts evaluate the author’s position on this topic??

  • Does the information come from authorities on the topic?

Did the author quote experts in the field?

Do his/her peers respect the source of the information?

Are the authorities CREDIBLE?

  • Is the information biased?

Does the author use words that are neutral (denotative) rather than strongly emotional (connotative)?

Has the author included only the extreme ideas available on this topic?

Does the author have an affiliation that could cause bias?

Will the author or source gain anything from this argument? (For example, if the author works for Greenpeace, and he is arguing that commercial fishing should be banned, is it possible that the source’s association with Greenpeace could skew the argument?)

  • Can you easily identify the author’s audience? point of view? purpose?

  • Is the argument developed logically?

Is the writing clear and well organized?

Does the author rely on documented facts to make his point, or does he rely on anecdotes?

Is the argument straightforward, or is it ambiguous – could be taken in several ways?

Does one point clearly lead to another, or do you feel as though the author has skipped something?

  • Does the author include the RIGHT KIND of evidence?

Does the fact the author cites really match his argument? or is the evidence just close to the topic? or just a bit out of date? or just a big out of the mainstream?

Are the sources complete? In other words, has the author included all aspects of the argument or information that he is incorporating? (Fallacy: Quote out of Context)

  • Does the author give ENOUGH evidence?

How many documented facts should the author include, depending on the length of the written work?

Remember, you are playing the skeptic here: If you had totally opposed the author’s premise when you started reading, has the author given you enough evidence now to convince you?

Has the author included enough factual, documented evidence, or has he filled the text with anecdotes and reasons that only expand the single fact he has included?

Opposing Viewpoint

Good persuasive writing at least acknowledges the opposing view of the argument. For the most part, authors should present the opposing argument in a fair and unbiased way – and then cite evidence to explain why the premise for the opposing viewpoint is wrong. Generally, the way that writers structure persuasive arguments is like this: 1st argument, 2nd argument, 3rd argument sub-topic, opposing viewpoint, 4th argument that is the strongest and best of the arguments. If the author does not include at least a statement of the opposing view, that makes the author less credible.


Finally, the reader needs to check several things about the conclusion. The more complex an argument is, the more closely you have to read the author’s conclusion to make sure that it does not go too far.

  • First, does the conclusion match up with the author’s premise? (Fallacy: Non-sequitur)

  • Second, has the author given enough evidence to justify the conclusion?


Sometimes an author will want you to actively get involved in order to accomplish the conclusion in the paper. For example, the author could give you information on how to register to vote, a contact phone number or e-mail for someone who is organizing a march, a name of your local representative so you can make your voice heard. This Call to Action is not in every persuasive paper; when the author does include a call to action, it comes at the end of the paper.



If you already agree with the author’s premise before you start to read, you need to be careful of logical vulnerability. You may be easily swayed by the author’s point even though the author does a poor job of logical development, includes many errors in the logic of reasoning, or does not give sufficient or appropriate evidence to support the premise.

A reader needs to be as skeptical about a premise with which he already agrees as with a premise to which he is opposed. A lack of skepticism is your logical vulnerability.

What is BIAS?

BIAS – preference or inclination that makes being objective difficult; prejudice;


one-sided presentation of an issue based on opinion rather than fact

2 Kinds of Bias

  1. language/loaded words

The words the author chooses are emotional and may unfairly influence the reader’s opinion on the topic.
Look at each of the following sentences Underline any words that are LOADED. These words have CONNOTATION, an emotional meaning that makes the words subjective. The use of these words shows BIAS on the part of the author.
What’s proper response to recent reports on air bags? Safety device not worth risk, cost, trouble” by Joan Beck St. Paul Pioneer Press December 4, 1996, page 10A

  • “It was only a fender-bender, a minor rear-ending of a car in the parking lot of a Boise, Idaho, shopping mall. But it set off a passenger side air bag that decapitated a 1-year-old girl sitting in a forward-facing child seat.”

  • “But instead of questioning the whole concept, the Big Brother federal government is reacting by blaming parents and pushing new rules about who should ride where in a car.”

  • “Smaller drivers, safety honchos are recommending, should push their seat back as far as possible and use extenders to reach foot pedals.”

  • “Every human life is infinitely precious and beyond price.”

2. Situational Bias

This means that the person expressing the opinion has an AFFILIATION with an organization that will make being fair and impartial difficult. Look at the credentials of the next two authors after you read the excerpts from their essays.

Animal rights forces missing at shelters” by Susan Paris

St. Paul Pioneer Press May 4, 1997, page 21A

  • “For the amount of money raised and spent by US animal rights groups, every cat and dog in America ought to have its own condominium.”

  • “At least one shelter, due to a lack of funds, had been forced to destroy unwanted animals using an old carbon monoxide chamber.

  • “So what has PETA done to help these homeless, hungry and sick animals and others that suffer and die in shelters each year?”

  • “Why do animal rights groups refuse to help shelter animals who need it most?”

  • “Its mission is to market its philosophy and lifestyle to the American public – a lifestyle predicated on the belief that the life of a rodent deserves the same moral consideration as the life of a child.”

Humane Society fights all animal abuse” by Wayne Pacelle

St. Paul Pioneer Press May 13, 1997 Page 6A

  • “Susan Paris’ opinion piece ... was a transparent attack on the humane movement by an industry hack.”

  • “... more than 90 percent of charitable dollars contributed by Americans to humane organizations are devoted to animal care and sheltering.”

  • “Ms. Paris is a foe of animal welfare.”

Now analyze the authors for SITUATIONAL BIAS:
Paris is president of Americans for Medical Progress, 401 King Street, Suite 401, Alexandria, Va. 22314. This is an organization that promotes use of animals for medical research.
How does Paris’ affiliation create situational bias?

Wayne Pacelle of Washington, D.C. is the vice president of the Humane Society of the United states. The Humane Society is the organization that is being attacked by Paris in her article.
How does Pacelle’s affiliation create situational bias?


DENOTATION = dictionary definition, literal meaning
CONNOTATION = the general sense of a word in addition to its literal meaning (a word's culture)


Denotation – (adj.) relatively low in cost; inexpensive
Connotation – (adj.) stingy; miserly


Denotation – (adj.) careful use of money and other resources
Connotation – (adj.) wisely economical

CHEAP has a negative connotation; THRIFTY has a positive connotation. Both have similar meanings when you look at their denotation.


Comment Example

emasculate denigrate scold compliment endorse extol

humiliate chastise comment approve praise


Denotation and Connation

skinny underweight lean slim svelte

anorexic thin trim slender



ugly homely cute handsome

hideous odd plain nice looking gorgeous

Recognizing Bias
Name: Date: Hour:

Critical reading has many aspects, one of which is bias. All words have CONNOTATION. A word’s connotation goes beyond the dictionary meaning of the word. Words can be neutral or have positive or negative connotations. Bias occurs when a person chooses a word that has an excessively positive or negative connotation. Look at these sentences:

Farmers who held their soybeans UNLOADED them later at higher prices.

Farmers who held their soybeans MARKETED them later at higher prices.
In the first sentence, UNLOADED is a word that carries a negative connotation. The reader would assume that the soybeans were somehow inferior since to unload something often means to sell something that is flawed to an unsuspecting buyer. In the second sentence, MARKETED is a word that carries a moderately positive connotation. The reader would assume that the farmer was astute and used sophisticated means to sell for the best price.
Now it’s your turn. In each of the following sentences, identify the word that carries the author’s bias. Underline that word or phrase . In the blank at the left of the sentence, put a + to show positive bias or a – to show negative bias.
1. Bob Hazelton railed against the evils of steroid use as he testified at the House subcommittee hearings on making steroids illegal.
2. Tom Gorowsky’s grit might have been more impressive than his goal-scoring.
3. The teacher’s nitpicking critique of the essay left the student depressed.
4. The Thought Police should worry about bigger issues than what the student wrote in his editorial for the Advocate.
5. The coach scrambled to get all the rosters organized for the game.
6. That politician is just pandering to potential voters with those recent campaign ads.
7. You can pay a lot for the gimmicks that impractical inventors dream up!
8. My mom reneged on her promise to let my get my driver’s license on my birthday.
9. Have you seen her prom dress? She looks positively angelic in it.
10. The telemarketer keep pestering my family with calls during the dinner hour.
11. That sleaze ball? You are related to that sleaze ball loser?
12. The manager’s attitude could really be harmful to those impressionable youths.
13. Because of the student’s diligent work ethic, making the honor roll was easy.
14. After all I have sacrificed for you, how can you be so ungrateful?
15. They reach in to their magic bag of tricks, and they’re off.

Evaluating a Source


National Enquirer




American Teacher


Rochester Post Bulletin



Pioneer Press


Star Tribune



NY Times




How do you measure print media's credibility? Look for these things:

  • Newspaper has a good reputation for factual reporting on local, national, and international stories

  • Articles give authors' names (by-lines)

  • Newspaper uses credible sources, such as AP, UPI, Newhouse News, Knight-Ridder, etc.

  • Appearance of the newspaper is professional

  • Information is similar to that which is reported in other local or national reputable paper

  • Investigative reporting is well-documented

RSS Fallacies




Faulty Analogy

compare two things that are not really alike

Teaching teens about sex and birth control is like taking an alcoholic into a bar.
(NOT a simile "like a rock")

Ad Hominem

"to the man"

(Name Calling)

attack your opponent, not your opponent's argument

"I am pleased USA Today recognized some Republican leaders in Congress for what they really are -- hatchet men."

Misuse of Humor

  1. funny at first

  1. then deeply critical

"At first I thought your cover was just a picture of a bovine transvestite. Then it struck me: a bull in a wedding gown -- why, it must be Dennis Rodman." Herbert B. Fox

Ad Populum

"to the people"

appeal to emotions of the reader


use of words such as "God", “liberty” "America," “fundamental rights”

In ads: babies, baby pets, families, flags
Negative: "communism" "radical"

False Authority

use quotes or information from a person who is not an expert

Brittney Spears says, “Only 9% of teenage girls get enough calcium. And studies show that people who drink milk lose more weight on diets.”




Appeal to Pity

(flies in their eyes)

tug on the heart strings but gives no facts

"I honestly never thought that it could happen to me, or to one of my friends, and never, ever, did I picture myself, along with hundreds of others, attending the funeral of a 17-year-old victim." Post-Bulletin 4/24/99 p. 13A

Snob Appeal

use/believe this and you'll be like the rich, famous, beautiful

Brittney Spears w/milk mustache.
Tiger Woods driving a Buick van.


everyone is doing it; everyone believes it

Everyone else gets a car when they turn 16!”

26,000,000 people use Word Perfect with a new user each 4.4 sec.



saying or implying there are only two choices, but the issue is very complex

You can either turn in your book report, or you can fail this class,” said Miss Barrett.
The poster read, “Respect Life or I’ll Kill You.”

Slippery Slope

we should not continue with or do A because if we do, horrible X, Y, and Z things will happen

If we allow the government to register handguns, next it will register hunting rifles; then it will forbid any citizen to own guns. We’ll end up with a police state or world where only criminals own guns.
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