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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