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ReasoningReasoning
Chapter 8Chapter 8
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Forms of ProofForms of Proof
Logos = Logical evidenceLogos = Logical evidence
Ethos = Ethics/CredibilityEthos = Ethics/Credibility
Pathos = Emotional Pathos = Emotional appealsappeals
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InferencesInferences
Mental leaps made Mental leaps made when listener agrees when listener agrees that evidence supports that evidence supports claimsclaims
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Argument Argument
Set of statements that Set of statements that develops evidence to develops evidence to establish validity of claimsestablish validity of claims
Patterns of reasoning help Patterns of reasoning help organize argumentorganize argument
Not a fight or angry Not a fight or angry disputedispute
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Patterns of ReasoningPatterns of Reasoning
Induction:Induction:
reasoning from specific reasoning from specific instancesinstances
Deduction:Deduction:
reasoning from a reasoning from a general principlegeneral principle
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Guidelines forGuidelines forInductive ReasoningInductive Reasoning
Enough examples for Enough examples for claimclaim
Accurate Accurate generalizationsgeneralizations
Support argumentsSupport arguments
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Reasoning inductivelyReasoning inductively
Inductive thinking; specific to Inductive thinking; specific to generalgeneral– Fermi II has operated since 1985 w/o Fermi II has operated since 1985 w/o
incidentincident– Davis Besse has been in operation since Davis Besse has been in operation since
1977 w/o a serious problem1977 w/o a serious problem– Perry plant in Cleveland, OH has been in Perry plant in Cleveland, OH has been in
operation since 1986 w/o a problemoperation since 1986 w/o a problem– Nuclear power can be managed safelyNuclear power can be managed safely
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Hasty GeneralizationsHasty Generalizations
Reaching a conclusion Reaching a conclusion without enough without enough evidence to support itevidence to support it
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Deductive ReasoningDeductive Reasoning
Major premiseMajor premise Minor premiseMinor premise ConclusionConclusion
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Major PremiseMajor Premise
The general principle, The general principle, states a familiar, states a familiar, commonly accepted commonly accepted beliefbelief
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Minor PremiseMinor Premise
The specific instance, The specific instance, establishes the truth of establishes the truth of the conclusionthe conclusion
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Deductive ExampleDeductive Example
Major premise:Major premise: The goal of The goal of social welfare programs is to social welfare programs is to move users to self-sufficiencymove users to self-sufficiency
Minor premise:Minor premise: Some programs Some programs create dependencycreate dependency
Claim:Claim: Therefore, some social Therefore, some social welfare programs should be welfare programs should be changedchanged
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Guidelines forGuidelines forDeductive ReasoningDeductive Reasoning
Establish the validity of Establish the validity of the major premisethe major premise
Strengthen it with Strengthen it with additional evidence or additional evidence or reasoningreasoning
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Causal Reasoning Causal Reasoning
Process of reasoning Process of reasoning that supports a claimthat supports a claim
by by establishing aestablishing a cause-and-effect cause-and-effect relationshiprelationship
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Guidelines forGuidelines forCausal ReasoningCausal Reasoning
Avoid false causesAvoid false causes Avoid assuming an event Avoid assuming an event
has only one causehas only one cause Cite supporting evidence Cite supporting evidence
to strengthen cause-and-to strengthen cause-and-effect relationshipseffect relationships
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Analogical ReasoningAnalogical Reasoning
Suggesting because Suggesting because two conditions or two conditions or events resemble each events resemble each other in certain ways, other in certain ways, they will resemble each they will resemble each other in other waysother in other ways
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Analogical ExampleAnalogical Example
Handguns are banned in Canada Handguns are banned in Canada and they have low crime ratesand they have low crime rates
If the U.S. banned handguns there If the U.S. banned handguns there would be a drop in violent crimeswould be a drop in violent crimes
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Reasoning by SignReasoning by Sign
Something exists or will Something exists or will happen based on happen based on something else that something else that exists or has happenedexists or has happened
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Reasoning by Sign Reasoning by Sign ExampleExample
A doctor reasons that a high A doctor reasons that a high temperature signals infection in temperature signals infection in the bodythe body
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Guidelines forGuidelines forReasoning by SignReasoning by Sign
Is alternative explanation Is alternative explanation more credible?more credible?
Assure sign is not an Assure sign is not an isolated instanceisolated instance
If instance in which a sign If instance in which a sign does not indicate a does not indicate a particular event, particular event, argument not solidargument not solid
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A Map of ReasoningA Map of Reasoning
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Grounds Grounds
Why do you think this Why do you think this or want to propose it?or want to propose it?
Check out Web Link 8.2: Toulmin Model at the Invitation to Public Speaking website.
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Warrant Warrant
How do you know your How do you know your grounds support your grounds support your claim?claim?
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Backing Backing
How do you know the How do you know the warrant supports the warrant supports the grounds?grounds?
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Claim Claim
What do you think or What do you think or want to propose?want to propose?
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Reasoning EthicallyReasoning Ethically
Build credibilityBuild credibility Use accurate evidenceUse accurate evidence Verify the structure of Verify the structure of
reasoningreasoning
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