Writing Arguments: A Rhetoric With
Readings
Eleventh Edition
Chapter 3
The Logical Structure of
Arguments: Logos
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Learning Objectives
LO 3.1 Explain the logical structure of argument in terms of
claim, reason, and assumption granted by the
audience.
LO 3.2 Use the Toulmin system to describe an argument’s
logical structure.
LO 3.3 Use the Toulmin system to generate ideas for your
argument and test it for completeness.
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An Overview of Logos: What Do We Mean by
the “Logical Structure” of an Argument? (1 of 3)
Learning Objective 3.1 Explain the logical structure of argument in terms of
claim, reason, and assumption granted by the audience.
Formal Logic Versus Real-World Logic
• Real-world arguments seldom “prove” anything
The Role of Assumptions
• Basis for real-world arguments
• Unshared assumptions are a problem
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An Overview of Logos: What Do We Mean by
the “Logical Structure” of an Argument? (2 of 3)
The Core of an Argument: The Enthymeme
• Incomplete logical structure
• A claim linked to a reason, expressed as a because
clause
• Audience must supply a missing premise and accept
underlying assumption (belief, value, or principle)
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Example of an Enthymeme
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An Overview of Logos: What Do We Mean by
the “Logical Structure” of an Argument? (3 of 3)
The Power of Audience-Based Reasons
• Argument is more effective if anchored in audience’s
beliefs and values
• Writer-based reasons might not be persuasive to
your audience
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Adopting a Language for Describing
Arguments: The Toulmin System (1 of 4)
Learning Objective 3.2 Use the Toulmin system to describe an argument’s
logical structure.
Overview of Toulmin’s System
• Audience-based, courtroom model
• All assertions and assumptions are contestable
• Anticipate counterarguments
• Question personal assumptions
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Adopting a Language for Describing
Arguments: The Toulmin System (2 of 4)
Overview of Toulmin’s System continued
• All verdicts are rendered by neutral third party
• Answer opposing viewpoints fully
• Provide reasons for supporting claim
• Provide reasons for disbelieving opposition
• Builds on enthymeme concept to analyze an
argument
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Adopting a Language for Describing
Arguments: The Toulmin System (3 of 4)
Toulmin’s System Terminology
• Warrant
• Underlying assumption audience must hold to guarantee
soundness of argument
• Grounds
• Supporting evidence that causes audience to accept
reasons
• Backing
• Argument that persuades audience to accept warrant
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Adopting a Language for Describing
Arguments: The Toulmin System (4 of 4)
Toulmin’s System Terminology
continued
• Rebuttal
• Considers how audience might challenge reason, grounds,
warrant, or backing
• Qualifier
• Provides degree of probable truth behind argument
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Using Toulmin’s Schema to Plan and Test
Your Argument (1 of 2)
Learning Objective 3.3 Use the Toulmin system to generate ideas for your
argument and test it for completeness.
Hypothetical Example: Cheerleaders as Athletes
Extended Student Example: Girls and Violent
Video Games
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Using Toulmin’s Schema to Plan and Test
Your Argument (2 of 2)
The Thesis-Governed “Self-Announcing” Structure
of Classical Argument
• Self-announcing (closed-form) structure
• States claim before body of argument
• Forecasts structure of argument
• Can forecast some, most, or all of argument
• Unfolding (open-form) structure
• Gives writer’s position late in essay
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A Note on the Informal Fallacies
Use of Informal Fallacies
• Not helpful for planning and testing arguments
• Can help recognize impacts of others’ arguments
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Copyright
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