Thinking Critically
Reasoning
Karen S. Wright
Induction is the process of reasoning from facts or
instances and arriving at a general claim.
Situation: You go to an Ari...
Deductive reasoning moves from the
general to the specific.
Several visits to the AZ Motor Vehicle Center were
unproducti...
Using Deductive Reasoning
Deductive reasoning might
go something like this:
• The AZ Motor Vehicle
Center wastes people’s
...
Syllogism
• Deductive arguments have
three
parts: two premises and a
conclusion.
• This three-part
structure is known as a...
Valid and Invalid Reasoning
The following argument is valid:
Premise 1 When it snows, the streets
get wet. (fact)
Premise ...
Valid and Invalid Arguments
Why is the following invalid?
Premise 1 When the battery is
dead, a car will not start.
Premis...
Why is the Following Valid?
Premise 1: When unemployment
rates rise, an economic recession
occurs.
Premise 2: The unemploy...
Inductive
Reasoning
Deductive
Reasoning
Argument begins With specific
evidence
With a general
claim
Argument
concludes
Wit...
Recognizing and Avoiding Logical
Fallacies
Logical fallacies are flaws
In reasoning
that lead to illogical statements
That...
Hasty Generalization
• Hasty generalization—when someone
generalizes from inadequate evidence.
• “My hometown is the best ...
Self-contradiction
• Self-contradiction
occurs when two
premises are used
that cannot
simultaneously be
true.
• “Only when...
Guilt by association
• Guilt by association implies
that an individual’s
argument, ideas, or opinions
lack merit because o...
Card-Stacking
• Ignores evidence on the other side of a question.
• Television commercials use this strategy.
When three s...
Taking Something Out of Context
• Taking something out of context
separates an idea or fact from the
material surrounding ...
Appeal to Ignorance
• Appeal to ignorance assumes that
the argument is valid simply
because it has not been shown to
be fa...
Ambiguity describes expressions that
are not clear because they have more
than one meaning.
An ambiguous expression may ...
A Complex or Loaded Question
• A complex question contains one or
more unproven assumptions.
• “Are you still spending tim...
Appeal to the People
• Appeal to the people draws
on whatever the people hold
dear—for example, country,
religion, family....
Name-calling
• Name calling attaches
an unpleasant label to
something or someone.
• Name-calling can stop
readers from thi...
Think and Write Logically
• Explain how your evidence is
clearly.
• Discuss the connection between
facts and the inference...
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Thinking critically3

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Thinking critically3

  1. 1. Thinking Critically Reasoning Karen S. Wright
  2. 2. Induction is the process of reasoning from facts or instances and arriving at a general claim. Situation: You go to an Arizona Vehicle Center to renew your driver’s license. You stand in line two hours to get your document.  Later you return for new license plates; clerk gives you wrong advice; you stand in line three hours. A third time you go there in response to a letter asking for information, and you discover that you need your car registration form, but the letter failed to tell you. You conclude that the AZ Motor Vehicle Center is inefficient. You have arrived at this conclusion by induction.
  3. 3. Deductive reasoning moves from the general to the specific. Several visits to the AZ Motor Vehicle Center were unproductive. They convince you that the AZ Motor Vehicle Center cares little about the convenience of its patrons. You will not be happy the next time you must return.
  4. 4. Using Deductive Reasoning Deductive reasoning might go something like this: • The AZ Motor Vehicle Center wastes people’s time. • I have to go to the AZ Motor Vehicle Center tomorrow. • Therefore, tomorrow my time will be wasted. You reached this conclusion by means of deduction.
  5. 5. Syllogism • Deductive arguments have three parts: two premises and a conclusion. • This three-part structure is known as a syllogism. • The argument is valid when the conclusion LOGICALLY follows the premises.
  6. 6. Valid and Invalid Reasoning The following argument is valid: Premise 1 When it snows, the streets get wet. (fact) Premise 2 It is snowing (fact) Conclusion Therefore, the streets are wet. The following argument is invalid: Premise 1 When is snows, the streets get wet. (fact) Premise 2 The streets are wet. Conclusion Therefore, it is snowing. The invalid argument has acceptable premises because the premises are facts. The argument’s conclusion is wrong. It ignores other reasons why the streets may be wet.
  7. 7. Valid and Invalid Arguments Why is the following invalid? Premise 1 When the battery is dead, a car will not start. Premise 2 My car will not start. Conclusion My battery is dead.
  8. 8. Why is the Following Valid? Premise 1: When unemployment rates rise, an economic recession occurs. Premise 2: The unemployment has risen. Conclusion: An economic recession will occur. The argument is valid. The writer of the argument must support the claim that the first premise is true.
  9. 9. Inductive Reasoning Deductive Reasoning Argument begins With specific evidence With a general claim Argument concludes With a general claim With a specific statement Conclusion is Reliable or unreliable True or false Reasoning is used To discover something new To apply what is known Comparison of Inductive and Deductive Reasoning
  10. 10. Recognizing and Avoiding Logical Fallacies Logical fallacies are flaws In reasoning that lead to illogical statements That SEEM logical.  They masquerade as reasonable statements.  They manipulate readers by appealing to their emotions.  Most logical fallacies are known by labels to indicate where reasoning has gone wrong in the thinking process.
  11. 11. Hasty Generalization • Hasty generalization—when someone generalizes from inadequate evidence. • “My hometown is the best place to live in the state” - - generalization is hasty with only two examples of why it is pleasant. • Stereotyping—a type of generalization that occurs if when someone makes prejudiced, sweeping claims about all members of a particular group. • Sexism—a type of generalization that occurs when someone discriminates based on sex.
  12. 12. Self-contradiction • Self-contradiction occurs when two premises are used that cannot simultaneously be true. • “Only when nuclear weapons have finally destroyed us will we be convinced of the need to control them”
  13. 13. Guilt by association • Guilt by association implies that an individual’s argument, ideas, or opinions lack merit because of that person’s activities, interest, or associates. • “Matilda, who is running for mayor, belongs to the International Hill Climbers Association, which declared bankruptcy
  14. 14. Card-Stacking • Ignores evidence on the other side of a question. • Television commercials use this strategy. When three slim, happy customers rave about a new diet plan, they do not mention that a) the plan does not work for everyone and b) other plans work better for some people. The makers of the commercial select evidence to promote their cause.
  15. 15. Taking Something Out of Context • Taking something out of context separates an idea or fact from the material surrounding it, thus distorting it for special purposes. • A movie critic writes: “The plot was predictable and boring but the music was sparkling.” • The advertisement for the movie says, “Critic calls this movie sparkling.”
  16. 16. Appeal to Ignorance • Appeal to ignorance assumes that the argument is valid simply because it has not been shown to be false. • Appeals to ignorance can be very persuasive because they prey on people’s lack of knowledge. • “Since no one has proven that depression does not cause cancer, we can assume it does.” • The absence of opposing evidence proves nothing.
  17. 17. Ambiguity describes expressions that are not clear because they have more than one meaning. An ambiguous expression may be taken either way by the reader. A statement such as “They were entertaining guests” is ambiguous. Were the guests humorous or were people giving hospitality to guests?
  18. 18. A Complex or Loaded Question • A complex question contains one or more unproven assumptions. • “Are you still spending time with known drug addicts?”
  19. 19. Appeal to the People • Appeal to the people draws on whatever the people hold dear—for example, country, religion, family. • This approach tries to sway people by using a favorable label instead of sound reasons. • “A vote for Richard Williams is a vote for the flag.”
  20. 20. Name-calling • Name calling attaches an unpleasant label to something or someone. • Name-calling can stop readers from thinking. • “Gertrude Jones was once an alcoholic, so she cannot possibly say anything of value about politics.” OH NO!!!!
  21. 21. Think and Write Logically • Explain how your evidence is clearly. • Discuss the connection between facts and the inferences they support. • You must guide your readers and not let them be fooled by confusing or false data.

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