chapter 3: reality assumptions
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Chapter 3: Reality Assumptions. This chapter will cover. Reality assumptions Patterns of deductive reasoning Using deductive reasoning to test logic, discover truth, make decisions, avoid stereotyping, and understand argument. Reality Assumptions. - PowerPoint PPT PresentationTRANSCRIPT
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Chapter 3: Reality Assumptions
This chapter will cover
• Reality assumptions
• Patterns of deductive reasoning• Using deductive reasoning to test logic,
discover truth, make decisions, avoid stereotyping, and understand
argument.
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Reality Assumptions
• Based on unique experience of individual
Beliefs about what is true and factual about the world.
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Detecting Reality Assumptions
Toulmin’s Model
• Issue: Should we use the SAT or ACT scores to predict success in
college?
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Toulmin’s Model
Claim - Students should not apply to colleges at which SAT scores are 200 points higher than theirs.
Reason Students will not likely succeed
Warrant (Reality Assumption)
Scores are accurate predictions of how well a student is prepared
Based on
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Toulmin’s Model
ReasonTest only
predicts level of struggle for
first year.
Warrant (Reality Assumption)
Students success based on character qualities
that are not measured by the tests.
ClaimColleges should not use standardized test
scores as a measure of success.
Based on
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Toulmin’s Model
Issue: Should trials and executions be televised
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Toulmin’s Model
Claim: Trials and executions should be televised
Reason: Public has the right to
have more information about the courts and the judicial system.
Warrant (Reality Assumption)
Televising trials would inform the public about our judicial
system.
Warrant (Value Assumption)
Freedom of information is an important value
Based on
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Reasoning
Deductive Reasoning
General statement to a specific instance
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Reasoning
Deductive
• Aims for Certainty
General to Specific
Inductive
• Gives us Probabilities
Specific to General
Chapter 6
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Deductive Reasoning
Syllogism- a classic example
• All men are mortal. (major premise)• Socrates is a man. (minor premise)• Therefore, Socrates is mortal. (conclusion)
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Deductive Reasoning
Validity
• Correct form makes an argument valid (logical).
• Accurate content makes it true.
• When the form is valid and the content is true, the argument is sound.
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Deductive Reasoning
is content true?All students eat pizza. Claire is a student at CSU. Is form valid?• Therefore, Claire eats pizza.
Is it sound?No
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Deductive Reasoning
is content true?All women are terrible drivers. Jane is a woman. Is form valid?• Therefore, Jane is a terrible driver.
Is it sound?Yes
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Deductive Reasoning
Pattern of Deductive reasoning
All As are Bs. Categorical statement m is A. Therefore, m is B
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Deductive Reasoning
B
A A statement in which members of one class are said
to be included in Another class.
Categorical Statement
All As are Bs.
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Conditional/hypothetical syllogism
Modus ponens:
‘the way of affirmation’: the antecedent leads to the consequent.
If A, then B
A Therefore, B
AB
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Conditional/hypothetical syllogism
If I have strep throat, then the culture will be positive.But the culture is not positive.So, I don’t have strep throat.
Modus tollens: ‘denying the consequent.’
If A, then B Not A Therefore not B
A B
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Deductive Reasoning
Questionable Premises
All drivers who speed are subject to a fine.
You are speeding. Which premise can be contested?
• Therefore, you are subject to a fine.
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Deductive Reasoning
Enthymeme
• Key part is implied rather than directly stated.
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Deductive Reasoning
Sound Argument:Correct Form
True PremisesUnsound Argument:
Incorrect Form,True Premises
Unsound Argument:Correct Form
Untrue PremisesUnsound Argument:
Incorrect Form, Untrue Premises
True False
Valid
Invalid
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Deductive Reasoning
Deductive reasoning can:
• Uncover Reality Assumptions• Discover Truth and Make Decisions• Combat Prejudice and Stereotyping
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Skill A critical thinker uses reasoning to discover
truth and prevent stereotyping
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Chapter 3: Reality Assumptions
Checkup
• Reality versus value assumptions• Validity in an argument• What makes a deductive argument sound• What does deductive reasoning aim to
establish