Logical reasoning and argumentation are key skills for effective public speaking. They help you build strong, persuasive arguments that can sway your audience. By mastering these techniques, you'll be able to craft compelling speeches that stand up to scrutiny.

Understanding different types of reasoning, like deductive and inductive, is crucial. You'll also need to watch out for common logical fallacies that can weaken your arguments. By combining solid logic with rhetorical appeals, you'll create powerful, convincing presentations.

Principles of Logical Reasoning

Foundations of Logical Reasoning

• Logical reasoning employs formal or informal logic to draw conclusions, make inferences, and evaluate arguments based on available evidence and premises
• Structure of an argument consists of premises (supporting statements) and a conclusion
  • Premises provide justification for the conclusion
• Validity in argumentation refers to the logical connection between premises and conclusion
  • Soundness requires both validity and true premises
• Critical thinking skills essential for effective logical reasoning
  • Analysis
  • Evaluation
  • Inference

Evidence and Argumentation

• Argumentation constructs and presents arguments to support a claim or position
  • Goals often include persuading others or reaching a conclusion
• Principle of charity interprets an opponent's arguments in their strongest possible form before attempting to refute them
• Various forms of evidence support claims and conclusions
  • Empirical data (scientific studies)
  • Expert testimony (field specialists)
  • Logical proofs (mathematical theorems)
  • Analogies (comparisons to similar situations)

Inductive vs Deductive Reasoning

Deductive Reasoning

• Moves from general premises to specific conclusions
  • If premises are true, the conclusion must be true
• Syllogism common form of deductive argument
  • Major premise
  • Minor premise
  • Conclusion
• Example:
  • Major premise: All mammals are warm-blooded
  • Minor premise: Dogs are mammals
  • Conclusion: Therefore, dogs are warm-blooded

Inductive Reasoning

• Draws probable conclusions from specific observations or evidence
  • Moves from particular instances to general principles
• Relies on strength of evidence and probability rather than absolute certainty
• Statistical reasoning uses data and probability to draw conclusions about populations or trends
  • Example: Survey of 1000 voters shows 60% support for a policy, concluding majority of all voters likely support it
• Principle of sufficient reason states every fact or truth must have an adequate explanation

Constructing Sound Arguments

• Requires careful consideration of premise truth, relevance, and sufficiency in supporting the conclusion
• Balances deductive and inductive approaches based on available evidence and argument goals
• Evaluates strength of premises and logical connections to ensure valid conclusions

Logical Fallacies in Arguments

Personal Attack Fallacies

• Ad hominem attacks the person making an argument rather than addressing the argument itself
  • Example: "You can't trust her environmental policy because she drives a gas-guzzling SUV"
• Genetic fallacy dismisses an argument based on its origin rather than its merits
  • Example: "That economic theory can't be valid because it was developed by a capitalist"

Misrepresentation Fallacies

• Straw man misrepresents an opponent's argument to make it easier to attack
  • Example: "Vegetarians think we should let animals rule the world" (oversimplification of animal rights arguments)
• False dichotomy presents only two options when other alternatives exist
  • Example: "Either we cut all social programs or we'll go bankrupt" (ignores middle-ground solutions)

Causal Fallacies

• Post hoc ergo propter hoc assumes one event caused another because it occurred first
  • Example: "I wore my lucky socks and we won the game, so my socks must be lucky"
• Hasty generalization draws broad conclusions from insufficient or unrepresentative samples
  • Example: "My neighbor is rude, so all people from his country must be rude"

Authority and Popularity Fallacies

• Appeal to authority relies on opinion of an authority figure in an unrelated field
  • Example: "This famous actor says climate change isn't real, so it must not be"
• Bandwagon fallacy assumes something is true or good because it's popular
  • Example: "Everyone is buying this product, so it must be the best"

Persuasive Argumentation

Rhetorical Appeals

• Classical rhetorical triangle consists of ethos, pathos, and logos
  • Ethos appeals to credibility (speaker's expertise or character)
  • Pathos appeals to emotion (audience's feelings or values)
  • Logos appeals to logic (facts, statistics, reasoning)
• Emotional appeals engage audience and create connection
  • Balance with logical reasoning to maintain credibility
• Vivid language, storytelling, and concrete examples enhance both logical and emotional appeals
  • Example: Using a personal anecdote about healthcare costs to support argument for policy change

Audience-Centered Approaches

• Adapt arguments to audience's values, beliefs, and experiences
  • Increases relevance and relatability of message
• Anticipate and address potential counterarguments
  • Demonstrates comprehensive understanding of issue
  • Strengthens overall persuasive power
• Leverage principle of cognitive dissonance
  • Highlight inconsistencies between audience's beliefs and actions
  • Example: Pointing out disconnect between stated environmental concerns and wasteful habits

Combining Reasoning Strategies

• Employ combination of deductive and inductive reasoning
  • Tailor to specific context and audience expectations
• Use statistical data to support broader claims (inductive)
  • Follow with logical implications of those claims (deductive)
• Structure arguments with clear progression
  • Start with agreed-upon premises
  • Build towards more contentious conclusions
• Provide multiple lines of evidence to support main points
  • Strengthen overall argument resilience