Informal Fallacies – Study Notes (Video Transcript)

Informal Fallacies: Key Concepts

Fallacy = Latin for trick or deceit; an error of reasoning that leads to an invalid conclusion or a poorly supported conclusion.
Falls into two broad categories:
- Formal fallacies: errors in the form/structure of an argument. The conclusion doesn’t follow from the premises due to a flaw in the logical form.
- Informal fallacies: errors arising from language use, vagueness, speaker intent, irrelevance, or persuasive tricks rather than the argument’s form.
Distinction emphasized in the lecture:
- Formal fallacies are about bad structure (e.g., if/then forms that invalidate the conclusion).
- Informal fallacies are about problematic reasoning in natural language that misleads or sways without a structural flaw.
The lecturer provides a worked example to illustrate the formal fallacy of affirming the consequent (common point of confusion in the talk):
- Pattern: If $P$, then $Q$; $Q$; therefore $P$.
- This is invalid because multiple things could make $Q$ true besides $P$.
- Logical representation (with $P$: “computer is unplugged”; $Q$: “computer will not work.”):
  P
  ightarrow Q,\ Q \
  ightarrow P
- Note: The speaker mixed terminology (claims of “affirming the antecedent” and “affirming the consequent”). The correct technical label for this form is affirming the consequent.
The lecture frames how informal fallacies arise in ethics and everyday discourse, and why knowing their names helps you avoid them in arguments and in evaluating political or media claims.

How to use these notes

Recognize common patterns in arguments you encounter in ethics, media, and politics.
For each fallacy, know the name, the core idea, a typical form, and a representative example.
Use the examples as cues to evaluate real-world claims and to structure your own arguments more rigorously.
Remember: many fallacies are persuasive because they appeal to emotions, authority, or common beliefs rather than evidence.

Common informal fallacies covered in the lecture

1) Ad Hominem (Argumentum ad hominem)

Definition: Attacking the person making the argument rather than engaging with the argument itself.
What it looks like: Dismissing a view by insulting the speaker or pointing to who they are rather than addressing the claim.
Example (described in lecture): A claim about pedestrian/cyclist safety is met with insult about the speaker’s identity or character instead of addressing the safety issue.
Significance: Undermines rational debate by shifting focus from the argument to the presenter.

2) Slippery Slope (Thin Edge of the W edge)

Definition: Argues that a relatively small first step will lead to a chain of related (negative) events culminating in disaster.
Core idea: The first step may be harmless, but it will inevitably lead to extreme outcomes.
Examples from lecture:
- Legalizing marijuana will lead to rampant hard drug use; hence marijuana should not be legalized.
- Abortion legalization leading to widespread routine abortions.
- Same-sex marriage leading to catastrophes some claim (e.g., societal collapse) without providing solid causal evidence.
Significance: Can overstate consequences and demand prohibitive caution without proven causal links.

3) Appeal to Force (Ad Baculum / Argumentum ad baculum)

Definition: Persuasion through threat or force rather than reasoned argument.
How it shows up: A demand to accept a conclusion “or else” instead of arguing the merits.
Example from the lecture: A threat to a decision-maker in a labor contract dispute used to coerce agreement rather than presenting reasons.
Significance: Appeals to fear undermine rational deliberation and violate fair deliberation norms.

4) Straw Man (Straw Figure / straw man argument)

Definition: Distorts or oversimplifies an opponent’s position to attack a weaker version of it and claim victory.
How it works: Attack a caricature of the opponent’s view instead of the actual argument.
Example from lecture: Discussing Peter Singer’s views on animal rights; an opposing claim is reframed as “Nazis think animals are above humans” and then attacked, rather than engaging Singer’s actual arguments.
Significance: Misrepresents arguments, making it easier to refute without addressing the real issue.

5) Appeal to Pity (Argumentum ad Misericordiam)

Definition: Evoking pity or emotion to obtain support for a conclusion, rather than using relevant evidence.
Example: A driver pleading that they were tired after midterms to dodge a speeding ticket.
Significance: Appeals to emotion can obscure objective evaluation of the facts.

6) Two Wrongs Fallacy (Tu quoque / Ad hominem in a different guise)

Definition: Defending oneself against a charge by pointing to the opponent’s similar fault.
How it shows up: “Didn’t you do X in the past? So your accusation isn’t valid now.”
Example from lecture: “You cheated on the biology exam; you cheated before—so my cheating now is justified.”
Significance: Deflects from the issue and normalizes wrongdoing by pointing to others’ mistakes.

7) Argument from Ignorance (Ad Ignorantiam)

Definition: Asserting a claim is true because it has not been proven false (or vice versa); using lack of evidence as support for a conclusion.
Example from lecture: Claim that aliens exist because no one has conclusively explained a glowing sky saucer observed by the speaker.
Significance: Shifts burden of proof and relies on absence of evidence rather than positive evidence.

8) Hasty Generalization

Definition: Drawing a broad conclusion from a small or unrepresentative sample.
Example from lecture: Criminal acts by a couple of Canadians lead to the blanket claim that all Canadians are criminals.
Significance: Ignores sample size, variability, and base rates; often tied to stereotypes (racism, xenophobia).

9) Appeal to Authority (Argumentum ad Verecundiam)

Definition: Accepting a claim as true because a famous person or perceived authority endorses it, regardless of expertise on the topic.
Example from lecture: A celebrity endorsing cryptocurrency; the claim is accepted because the celebrity is famous, not because of expertise in finance.
Alternative label used in lecture: “Appeal to a famous person” fallacy.
Significance: Misleads when expertise is absent or irrelevant; highlights the need to evaluate sources by domain-specific expertise.

10) Fallacy of Composition

Definition: Assuming that what is true of the parts is true of the whole.
Examples from lecture:
- “Every sentence in this essay is excellent; therefore, the essay is excellent.”
- A sports team with star players might still perform poorly as a team due to poor collaboration.
Significance: Parts having a property does not guarantee the whole has that property; depends on how parts interact.

11) Fallacy of Division (Division)

Definition: Opposite of composition; assuming that what is true of the whole is true of its parts.
Examples from lecture:
- A jigsaw puzzle assembled into a circular shape implies every individual piece is circular.
- If a group is average or above average, then every individual member must share that trait.
Significance: Incorrectly transfers characteristics from collective to individual units.

12) False Dilemma (False Choice)

Definition: Presenting two options as if they are the only possibilities, when in fact more options exist.
Lecture’s framing: Ayn Rand’s dichotomy of altruism vs egoism; the claim that one must be either wholly altruistic (selfless) or wholly selfish.
Why it’s false: Reality often supports mixtures (you can be partly altruistic and partly egoistic); there are more than two options.
Significance: Forces a binary choice and discourages nuanced positions or middle grounds.

Additional notes and cross-cutting themes from the lecture

The point of studying these fallacies: They occur frequently in ethics discussions and contemporary discourse; knowing them helps you avoid errors and critique arguments more effectively.
Real-world relevance: Fallacies show up in news, political speeches, social media debates, and everyday conversations.
The speaker emphasizes the non-exhaustiveness of a catalog of fallacies: there are infinitely many ways reasoning can go wrong; textbooks typically cover around 12–30 common ones, with 12 highlighted here as especially frequent.
Ethical and practical implications: In ethical reasoning, recognizing fallacies helps you resist manipulative arguments and supports clearer, more justifiable conclusions.
Examples often mix humor and real-world tangents to illustrate how fallacies appear in ordinary discussion (e.g., cycling hostility, policy debates, celebrity endorsements, etc.).
Connections to broader principles:
- Avoid relying on language tricks; rely on the strength of reasons and evidence.
- Be wary of red flags like unfounded generalizations, misrepresented positions, or emotion-driven appeals.
- When evaluating arguments, consider alternative possibilities (avoid false dilemmas) and assess whether conclusions generalize from parts to wholes or vice versa.

Quick-reference cheat sheet (names and essence)

Ad Hominem: Attack person, not argument.
Slippery Slope: One step leads to extreme consequences without sufficient evidence.
Appeal to Force (Ad Baculum): Coerce acceptance with threats, not reasons.
Straw Man: Misrepresent opponent’s position to attack a weaker version.
Appeal to Pity (Ad Misericordiam): Use emotion instead of evidence.
Two Wrongs (Tu Quoque): Defend self by pointing to others’ faults.
Argument from Ignorance (Ad Ignorantiam): Lack of evidence used as evidence for a claim.
Hasty Generalization: Broad conclusion from small or biased sample.
Appeal to Authority (Ad Verecundiam): Rely on celeb/authority rather than expertise.
Composition: What’s true of parts is true of the whole.
Division: What’s true of the whole is true of the parts.
False Dilemma: Present only two options when others exist.

End of notes

Practical takeaway: Next time you hear a claim, ask yourself: (1) Is the form valid? (2) Is there a fallacy in language or persuasion (e.g., appeal to emotion, ad hominem, straw man)? (3) Are there alternative explanations or more nuanced positions beyond a simple either/or choice?