Transcript Chapter 3: Reality Assumptions

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
Beliefs about what is true and
factual about the world.
• Based on unique experience of individual
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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
Based on
Warrant
(Reality Assumption)
Scores are accurate
predictions of how
well a student is
prepared
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Toulmin’s Model
Claim
Colleges should not use standardized test
scores as a measure of success.
Reason
Test only
predicts level
of struggle for
first year.
Warrant
(Reality Assumption)
Based on
Students success based
on character qualities
that are not measured by
the tests.
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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
Warrant
Reason:
Public has the right to
have more
information about
the courts and the
judicial system.
(Reality Assumption)
Televising trials would inform
the public about our judicial
system.
Based on
Warrant
(Value Assumption)
Freedom of information is an
important value
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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.
m is A.
Therefore, m is B
Categorical statement
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Deductive Reasoning
Categorical Statement
All As are Bs.
A
B
A statement in which
members of one
class are said
to be included in
Another class.
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Conditional/hypothetical syllogism
Modus ponens:
‘the way of affirmation’: the antecedent leads to
the consequent.
If A, then B
A
A Therefore, B
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B
Conditional/hypothetical syllogism
Modus tollens:
‘denying the consequent.’
If A, then B
A
B
Not A
Therefore not B
If I have strep throat, then the culture will be positive.
But the culture is not positive.
So, I don’t have strep throat.
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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
True
False
Valid
Sound Argument:
Correct Form
True Premises
Unsound Argument:
Correct Form
Untrue Premises
Invalid
Unsound Argument:
Incorrect Form,
True Premises
Unsound Argument:
Incorrect Form,
Untrue Premises
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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
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