PHIL 101-02: Rhetoric, Fallacies, and Bad Arguments

Course Overview and Fundamental Rules of Argumentation

• Course Information: PHIL 101-02, Lecture Date: September 23, 2026.

• Topic: Rhetoric, Fallacies, and Bad Arguments.

• The Burden of Proof:

  • Fundamental Axiom: If you make a claim, you owe reasons for it.

  • Placement: The burden of proof rests squarely on the person who makes a claim or assertion.

Burden of Proof Fallacies

• Shifting or Reversing the Burden of Proof:

  • Definition: Trying to make an opponent responsible for disproving a claim instead of providing evidence yourself, or responding to criticism by insisting that the critic must prove the opposite of your claim.

  • Examples:

  • "I say ghosts exist. If you can't prove they don't, then they do."

  • "You say my claim is wrong? Then prove the opposite is right."

  • Logical Flaw: The claimant must provide reasons; a lack of disproof from an opponent does not constitute proof. Critics may point out a lack of evidence without needing to defend a contrary claim.

• Proof by Challenge ("Prove Me Wrong"):

  • Definition: Asserting a claim and demanding that others refute it, without offering any supporting reasons.

  • Example: "Climate change is a hoax—prove me wrong."

  • Logical Flaw: A challenge is not an argument. The burden remains on the person making the claim.

• Argument from Ignorance (Argumentum ad Ignorantiam) / Appeal to Ignorance:

  • Definition: Claiming something is true because it hasn't been proven false—or false because it hasn't been proven true.

  • Examples:

  • "No one has shown that this diet doesn't work, so it must work."

  • "We certainly know that there is no extraterrestrial life. If there were, we would have found it by now."

  • "No one has proven ghosts don't exist, therefore they must exist."

  • "You can't prove the government is not spying on us, so they are."

  • "Why can nobody explain who runs the chemtrail program? This goes to show how far the government conspiracy extends."

  • Logical Flaw: Absence of evidence is not evidence of truth, nor is absence of evidence evidence of absence. Ignorance is not evidence for anything; it is simply ignorance.

  • Visual Representation:     

    

• Evaluating and Responding to Burden of Proof Fallacies:

  • Diagnostic Questions for Identification:

  • Who made the claim?

  • Has that person provided reasons or evidence?

  • Is someone demanding refutation instead of offering support?

  • Is the argument relying on lack of evidence rather than presence of evidence?

  • Tactical Responses:

  • Name the fallacy: "That shifts the burden of proof."

  • Restate the rule: "You made the claim; you need to support it."

  • Decline the challenge: "A challenge isn't evidence."

  • Ask for reasons: "What reasons do you have for believing this?"

Strategies and Options for Refuting Arguments

• Option 1: Flaw in Logical Structure:

  • Show that the argument as a whole is flawed in some way.

  • For deductive arguments, this means showing that the argument is not valid.

• Option 2: Premise Disproof:

  • If the argument is deductively valid, show that one or more of the premises is false.

  • This amounts to showing that the argument is not sound.

• Option 3: Counterexamples and Reductio ad Absurdum:

  • Provide a counterexample to the conclusion (i.e., something that contradicts the conclusion).

  • Employ reductio ad absurdum to demonstrate that the conclusion leads to contradiction or absurdity.

  • Visual Representation:     

    

Classical Rhetoric and Persuasion

• Definition of Rhetoric:

  • The art of effective communication—especially the strategic use of language to persuade or influence an audience.

• Historical Context and Intellectual Status:

  • Modern Skepticism: Rhetoric often gets a bad name (e.g., dismissed as "mere rhetoric" or "empty rhetoric").

  • Philosophical Origins: This negative reputation traces to Plato's and Socrates's distrust of the sophists.

  • Classical Pedagogy: Aristotle wrote a foundational treatise titled Rhetoric, and rhetoric was an integral part of the medieval trivium in classical education.

• Aristotelian Modes of Persuasion:

  • Ethos: "Character" or credibility.

  • Pathos: "Emotion" or psychological appeal.

  • Logos: "Argument" or logical reasoning.

• Ethical Dual Use:

  • Aristotle recognized that rhetoric could be used for good or evil.

  • Character (ethos) can be faked, emotions (pathos) can be manipulated, and arguments (logos) can be deceptively bad.

  • Visual Representation:     

    

Formal Versus Informal Fallacies

• Formal Fallacies:

  • Definition: Errors in deductive reasoning that make an argument invalid purely based on its structure.

  • Modus Ponens (Valid Structure):

  • Formula: $P \rightarrow Q$, $P$, therefore $Q$

  • Affirming the Consequent (Invalid Formal Fallacy):

  • Formula: $P \rightarrow Q$, $Q$, therefore $P$

  • Modus Tollens (Valid Structure):

  • Formula: $P \rightarrow Q$, $\sim Q$, therefore $\sim P$

  • Denying the Antecedent (Invalid Formal Fallacy):

  • Formula: $P \rightarrow Q$, $\sim P$, therefore $\sim Q$

• Informal Fallacies:

  • Definition: Errors in reasoning not solely dependent on the structure of the argument.

  • Mechanisms: May rely on the content, context, or language used to persuade or mislead the audience.

Key Informal Fallacies of Relevance and Presumption

• Appeal to the Majority (Argumentum ad Populum):

  • Definition: Inferring that a claim is true simply because many or most people believe it.

  • Example: "This post saying the new study is fake has thousands of likes, so the study must be wrong."

  • Core Epistemological Truths:

  • The fact that you believe something does not make it true.

  • The fact that someone (anyone!) else believes something does not make it true.

  • The fact that any number of people believe something does not make it true.

  • Visual Representation:     

    

• The Straw Man Fallacy:

  • Definition: Misrepresenting or distorting an opponent's argument to make it easier to attack or refute. Instead of addressing the actual claims or positions put forth by the opposing side, a weakened or exaggerated version is presented and countered.

  • Example:

  • Teacher 1: "We should spend more time teaching math."

  • Teacher 2: "Oh, so literacy doesn't matter at all? You think we should eliminate literature and arts from the curriculum entirely!"

  • Visual Representation:     

    

• Begging the Question (Petitio Principii / Circular Reasoning):

  • Definition: Assuming the truth of what the argument is trying to prove; assuming the truth of the conclusion in the premises; using the conclusion as a premise in the argument.

  • Classical Deductive Example:

  • Premise 1: The Bible says that God exists.

  • Premise 2: We know that what the Bible says is true because it is the word of God.

  • Conclusion: Therefore, it is true that God exists.

  • Monk Cartoon Example:

  • Statement: "The soul is immortal. Since it lives forever. Since it does not die. Thus, it is immortal."

  • Visual Representation:     

    

• Argument Ad Hominem:

  • Definition: Argument "against the person"—an argument that attacks the opponent as a person, rather than addressing his or her arguments.

  • Standard Workplace Example:

  • Person 1: "Based on the data, I think we should reduce our department's travel budget this year."

  • Person 2: "Why should anyone listen to you? You've never managed money well in your own life."

  • Tu Quoque Variant ("You Too" / "You Did It Too"):

  • Definition: Attempting to discredit an argument by pointing out that the person making it has acted inconsistently with their own stance.

  • Example:

    • Person 1: "You shouldn't smoke; it's bad for your health."

    • Person 2: "Like I'm going to listen to you. You smoked a pack a day for decades!"

  • Analytical Question: Is it fallacious to call out hypocrisy? Yes; calling out hypocrisy does not falsify the argument, because personal conduct does not change the factual truth of the statement.

  • Visual Representation:     

    

Fallacies of Causation and Ambiguity

• Post Hoc Ergo Propter Hoc:

  • Definition: Latin for "after this, therefore because of this." Concluding that because one event follows another, the first event caused the second.

  • Core Principle: Correlation does not imply causation. An appropriate temporal relationship is necessary to establish causation, but it is not sufficient.

  • Examples:

  • "Every morning, the sun rises just after the rooster crows, so the rooster 'brings on the day.'"

  • In the 1990s and 2000s, the fact that children were often diagnosed with autism in the months after receiving the MMR vaccine was taken as evidence that the vaccine caused autism.

  • Visual Representation:     

    

• Equivocation:

  • Definition: Occurs when a key term or phrase is used with different meanings at different places in an argument, exploiting ambiguity to make the argument appear stronger than it actually is.

  • Example:

  • Premise 1: All citizens have a right to live in a free society.

  • Premise 2: Anyone who is not currently in prison is free.

  • Conclusion: Therefore, anyone who is not currently in prison fully enjoys the rights of a free society.

  • Visual Representation:     

    

Practical Case Studies and Fallacy Analysis

• Case Study 1: A Public Health Discussion:

  • Argument Text: "People who oppose mandatory flu shots clearly think viruses are harmless, which is ridiculous. And mandatory flu shots are justified because they're necessary for public safety—if they weren't necessary, we wouldn't need them. Besides, you're lecturing me about health policy when you don't even exercise regularly."

  • Identified Fallacies:

  • Straw Man: Misrepresenting opponents as believing "viruses are harmless."

  • Begging the Question: Claiming "Mandatory shots are necessary because they're needed."

  • Ad Hominem (Tu Quoque): Dismissing the person's argument because they don't exercise regularly.

• Case Study 2: A Workplace Policy Debate:

  • Argument Text: "Ever since the company let people work from home on Fridays, productivity has tanked—just look at how chaotic last week felt. And honestly, your whole defense of remote work is meaningless because you've never been a serious employee anyway. Plus, if remote work really improved efficiency like you claim, someone would have proven it by now, but no one has."

  • Identified Fallacies:

  • Post Hoc Ergo Propter Hoc: Assuming last week's chaos was caused by Friday remote work.

  • Ad Hominem: Attacking the colleague's seriousness as an employee.

  • Appeal to Ignorance: Claiming that "No one has proven remote work improves efficiency, therefore it doesn't."

• Case Study 3: A Workplace Wellness Proposal:

  • Argument Text: "Look, the company says this wellness program will make us healthier, but that's ridiculous—just because it gives us access to a health app doesn't mean it can force us to stop getting sick. And remember last year when they introduced that new scheduling software? Productivity dropped right afterward, so clearly any new program they roll out is going to hurt us. Plus, your whole defense of the wellness plan boils down to claiming it will 'transform our lives,' which is just naïve cheerleading—nobody believes an app can magically fix everything."

  • Identified Fallacies:

  • Equivocation: Equivocates on "healthier." The company uses it to mean improved general well-being, whereas the critic uses it to mean completely free from all illness.

  • Post Hoc Ergo Propter Hoc: "The scheduling software was introduced, and productivity dropped afterward—so any new program will hurt us." Infers causation from mere temporal sequence and generalizes it to all new programs.

  • Straw Man: "Your defense of the wellness plan is just naïve cheerleading—you think an app will magically fix everything." Misrepresents the other person's actual position by exaggerating it into an implausible claim.

• Case Study 4: A Neighborhood Zoning Meeting:

  • Argument Text: "We shouldn't allow the new community center because the last time a big building went up, traffic got worse—so obviously this center will ruin the neighborhood too. And if you can't prove that the center won't attract crime, then we have to assume it will. Also, your support for the project is meaningless since you've always been in the pocket of developers."

  • Identified Fallacies:

  • Post Hoc Ergo Propter Hoc: Assuming the previous building caused traffic and that this one will too.

  • Appeal to Ignorance: Claiming "You can't prove it won't cause crime, so it will."

  • Ad Hominem: Accusing the person of being "in the pocket of developers."