Week 13 — Lecture Outline · Argument, Reasoning & Logical Fallacies

Course: Public Speaking — Fundamentals of Oral Communication (COMM 1) · Silver Oak University (fictional sample) · Prof. Marchetti
Objective covered: Objective 7 — Evaluate and construct persuasive arguments using the principles of sound reasoning; identify and explain common logical fallacies in described arguments.
SLOs touched: B (critical listening & analysis — evaluating arguments, identifying fallacies) · A (compose & deliver — building a sound argument for a speech)
Meeting pattern: 2 sessions × 75 min = 150 min. Segment minutes below total ~150; scale to your own pattern.

---

Week at a Glance

The week's big question	"What makes an argument actually hold up — and what makes it look convincing while secretly collapsing?"
By the end of the week, students can…	(1) name and distinguish the four types of reasoning — inductive, deductive, causal, analogical; (2) diagram the Toulmin model — claim, evidence/grounds, warrant — and explain the warrant's role; (3) identify and name twelve common logical fallacies from described examples; (4) explain the classic mix-ups: sequence ≠ cause; valid authority vs. false authority; ad hominem vs. straw man vs. red herring.
Key vocabulary	reasoning · inductive reasoning · deductive reasoning · causal reasoning · analogical reasoning · syllogism · Toulmin model · claim · evidence / grounds · warrant · backing · qualifier · rebuttal (Toulmin's terms, factual) · logical fallacy · hasty generalization · false cause (post hoc ergo propter hoc) · ad hominem · straw man · false dilemma (either-or) · bandwagon (ad populum) · slippery slope · false authority · red herring · begging the question (circular reasoning) · appeal to ignorance · weak analogy
Materials	slides (Deck 13), readings + video links, one approved chatbot for the AI-critique moment; no phone-camera recording needed this week (concept workshop — students assess a written argument, not a recording)
Timing note	8 segments, ~150 min total. Session 1 = Segments 1–4 (~75). Session 2 = Segments 5–8 (~75).

---

Segment 1 — Hook & the Promise (10 min) · Session 1 opens

Hook. Open with a claim, not a syllabus: "Everyone who disagrees with me on this topic obviously hasn't thought it through." Pause. "What's wrong with that sentence as an argument?"

Take three or four responses. Guide toward the core issue: it attacks the person (or implies their reasoning is defective) rather than addressing the argument. That has a name — ad hominem — and today you're going to learn eleven more like it. By the end of this week, you'll recognize every one of these in the wild.

The turn: "Here's the thing — bad arguments don't announce themselves. They dress up in confidence, statistics (real or invented), and authority (real or fake). Today we give you the X-ray vision."

The promise (write it on the board): "By Friday you'll be able to diagram a sound argument from scratch using the Toulmin model, name the four types of reasoning, and identify twelve fallacies — precisely enough to explain exactly why each one is flawed."

Why it matters line (memory hook): "A fallacy isn't just a wrong answer. It's a reasoning error that masquerades as a right one."

---

Segment 2 — The Four Types of Reasoning (22 min)

Set it up: "Before we talk about what goes wrong in reasoning, let's name what good reasoning looks like."

Build each type with a plain example:

1. Inductive reasoning — drawing a general conclusion from specific observations or examples.
- Plain example: You try three of the dining hall's Tuesday specials; all three are disappointing. You conclude: "The Tuesday specials here aren't worth it." You've reasoned from specific cases to a general rule.
- Strength: builds generalizations from real-world evidence.
- Vulnerability: the generalization is only as strong as the number and diversity of the cases. Generalize too fast from too few → hasty generalization fallacy (that's coming in Segment 6).

2. Deductive reasoning — moving from a general principle to a specific conclusion (the classic form: a syllogism).
- Plain example: "First-year students who complete Study Skills workshops perform better in their first-term finals. Maya is a first-year student who completed the workshop. Therefore, Maya is likely to perform well in her first-term finals."
- Strength: if the premises are true and the logic is valid, the conclusion must follow.
- Vulnerability: if either premise is false or overstated, the conclusion fails even with valid form.

3. Causal reasoning — arguing that one event or condition causes, produces, or leads to another.
- Plain example: "Students who sleep fewer than six hours before an exam score significantly lower than those who sleep seven or more hours." (note: this is the pattern, and the proposed cause is sleep deprivation)
- Strength: identifies mechanisms — "this is why that happens" — which is more actionable than correlation alone.
- Vulnerability: sequence and correlation are not cause. Just because B follows A does not mean A caused B — that's the false-cause (post hoc) fallacy (Segment 6). Establishing real causation requires ruling out alternative explanations.

4. Analogical reasoning — arguing that because two things are similar in known ways, they are likely similar in another way.
- Plain example: "Campus bike parking worked well at Greenfield College after they installed covered racks; it would likely work at Silver Oak for similar reasons."
- Strength: draws on real-world evidence from comparable situations.
- Vulnerability: the analogy must hold up. If the two situations differ in ways that matter, the argument weakens — that's the weak analogy fallacy (Segment 6).

Quick interaction (~4 min): name a scenario; have students classify which type of reasoning it uses (or whether it commits a fallacy). Suggested: "Every time we hired a new manager, sales went up — so hiring a new manager causes sales to increase." (Causal claim → but likely false cause; sequence ≠ cause.)

---

Segment 3 — The Toulmin Model (20 min)

Set it up: "Here's a precision tool for building and checking any argument. It comes from philosopher Stephen Toulmin — real person, real model, factual."

Build the core three parts (the ones students must know):

• Claim: the conclusion you are asserting — what you want the audience to believe or do. "Silver Oak should add covered bike-parking racks in the main quad."
• Evidence / Grounds: the data, facts, examples, testimony, or research that supports the claim. "A spring survey by the Student Senate found that 60% of cycling commuters reported a damaged or stolen bike in the past year due to inadequate covered parking." (This is an illustrative model figure — in a real speech, cite your actual verified source.)
• Warrant: the logical principle or assumption that connects the evidence to the claim — the because that makes the evidence prove the claim. "When a substantial majority of users report preventable damage or theft, addressing the root cause is a justified campus priority."

Why the warrant is the crucial piece: most everyday arguments have a claim and some evidence, but the warrant is left unstated. That's where fallacies sneak in. If the warrant doesn't hold (or the evidence doesn't actually support the claim), the argument breaks — even if it sounds confident.

Three additional Toulmin elements (introduce briefly; students don't need to memorize for this course, but they are part of the real model, named factually):
- Backing: additional support for the warrant itself.
- Qualifier: language that limits the force of the claim ("likely," "in most cases," "tends to").
- Rebuttal: anticipated counter-arguments — "unless the campus budget is already allocated to higher-priority repairs."

One fully worked "model speech moment" — a complete Toulmin argument:

Claim: Campus food service should extend weekday hours until 10 p.m.
Evidence / Grounds: A survey conducted by the Associated Students last semester found that 73% of students who finish evening classes after 8 p.m. have no access to a hot meal on campus, and that 44% report skipping dinner as a result on at least three days a week. (Note: this is an illustrative example — the specific numbers are not real survey figures; in a real speech, cite your actual source.)
Warrant: When a majority of evening students lack access to a basic nutritional resource during core academic hours, extending service to meet that documented need is a reasonable institutional accommodation.
Qualifier: "Depending on staffing costs" — noted explicitly.
Rebuttal: "Unless evening demand doesn't justify the cost after accounting for food waste" — the argument addresses this.

Misconception + cure:
- ❌ "The warrant is just saying the evidence proves the claim."
✅ Cure: the warrant explains why or on what principle the evidence proves the claim. "The campus survey found 73% lack dinner access" is evidence. "When 73% of a group lacks a basic resource during their working hours, addressing that gap is an institutional responsibility" is the warrant — the principle that links them.

---

Segment 4 — Interaction: Build the Toulmin Argument (10 min) · Session 1 closes (~75)

Think-Pair-Share (~8 min): put a claim on the board: "Silver Oak should require incoming students to complete a two-hour digital-literacy module before registering for their first term."

Students work in pairs:
1. What evidence would you need? (Must be real or explicitly illustrative — never invented)
2. What is the warrant — the principle that links evidence to claim?
3. What qualifier would honest reasoning add?

Take two or three pairs. Probe: "Is that evidence, or is that another claim? Is that the warrant, or is it more evidence?"

Memory hook: "Claim says what. Evidence shows why. Warrant says that's why the evidence proves the claim. If your warrant doesn't hold, neither does the argument."

Tease Session 2: "Now that we can build a sound argument, we spend Session 2 on how arguments go wrong — a field guide to twelve fallacies."

---

Segment 5 — The Logical Fallacies: Introduction + Group One (22 min) · Session 2 opens

Set it up: "A logical fallacy is a flaw in reasoning — a mistake in how the argument is constructed — that makes it look valid when it isn't. These are not rare. You'll hear them in advertising, on social media, in conversations, and yes, sometimes in speeches that should know better."

The field guide — Group One: Problems with Evidence and Generalization

1. Hasty Generalization — drawing a broad conclusion from too few, or unrepresentative, cases.
- "I called campus security twice and they were slow both times — campus security never responds quickly."
- What's flawed: two cases are not a representative sample for a universal conclusion.

2. False Cause (Post Hoc Ergo Propter Hoc) — assuming that because B came after A, A caused B. Sequence ≠ cause.
- "Every time our college installed a new president, the following semester's enrollment increased. New presidents cause enrollment growth."
- What's flawed: correlation of timing is not causation; many other factors affect enrollment.

3. Weak Analogy — arguing by comparison when the two things are not sufficiently similar in the ways that matter.
- "If a new lock can stop burglars at home, a new lock system will stop bike theft on campus."
- What's flawed: home locks and bike locks operate in very different environments (volume, access, supervision) — the analogy doesn't hold.

4. Appeal to Ignorance — claiming something is true (or false) simply because it hasn't been proven otherwise.
- "No one has proven that this study-hall renovation won't help retention — so it must be a good investment."
- What's flawed: absence of disproof is not proof; the burden of evidence for the positive claim belongs to the one making it.

---

Segment 6 — The Fallacy Field Guide: Groups Two and Three (22 min)

Group Two: Problems with Source and Authority

5. False Authority — appealing to someone as an expert who lacks genuine authority on the relevant topic.
- "A famous athlete recommends this brand of nutritional supplement — it must be effective."
- What's flawed: athletic fame ≠ nutritional science expertise.
- Key contrast: a registered dietitian citing published clinical research is a valid appeal to authority. The difference is whether the source has genuine expertise in the relevant field.

6. Bandwagon (Ad Populum) — arguing that something is true or good because many people believe or do it.
- "Everyone on the soccer team uses this warm-up protocol, so it must be the best approach."
- What's flawed: popularity does not confer truth or quality; once everyone believed something false.

Group Three: Problems with Attacking Instead of Arguing

7. Ad Hominem — attacking the person making the argument rather than the argument itself.
- "Don't take his advice on the study-group format — he failed two courses last term."
- What's flawed: the person's academic record has no bearing on whether their advice is logically sound.

8. Straw Man — misrepresenting the opponent's position (making it easier to attack) and then attacking the misrepresentation.
- Original position: "We should add a 15-minute wellness break to three-hour evening labs." Straw man version: "So you want to cancel half the lab just for students to go on walks?"
- What's flawed: the misrepresentation is not what was proposed; disproving the exaggerated version leaves the actual argument untouched.

9. Red Herring — introducing an irrelevant topic to divert attention from the actual argument.
- "Why should we discuss bike-rack funding when there are far bigger problems on this campus, like rising tuition?"
- What's flawed: rising tuition is a separate issue; citing it neither addresses nor refutes the bike-rack argument.

Key distinction drill (put on one slide):
- Ad hominem attacks the person.
- Straw man attacks a distorted version of the position.
- Red herring changes the subject entirely.

---

Segment 7 — The Final Fallacies + AI-Critique Moment (20 min)

Group Four: Structural / Logical Problems

10. False Dilemma (Either-Or) — presenting only two options when more exist, typically forcing a choice between an extreme and its opposite.
- "Either you support requiring helmets for every cyclist on campus, or you don't care about student safety."
- What's flawed: there are other positions (e.g., strongly encouraged but not mandatory; subsidized helmet availability).

11. Slippery Slope — claiming that one event will inevitably lead to a chain of negative consequences, without adequate evidence for each step.
- "If we allow food and drinks in the library study rooms, soon students will hold parties there, then staff will spend all their time cleaning up, and then the library will have to close entire wings."
- What's flawed: each step requires evidence; the chain of inevitability is asserted, not demonstrated.

12. Begging the Question (Circular Reasoning) — using the conclusion as a premise — the claim assumes what it's trying to prove.
- "Campus housing should be mandatory for first-year students because first-year students should live on campus."
- What's flawed: "should live on campus" is exactly the claim being argued — it can't also be the evidence.

The classic mix-up table (put this on a slide for reference):
| Fallacy | Core error |
|---|---|
| False cause (post hoc) | Sequence ≠ cause |
| Hasty generalization | Too few cases → too big a claim |
| Ad hominem | Attack the person, not the argument |
| Straw man | Attack a distorted version of the argument |
| Red herring | Change the subject |
| False dilemma | Only two choices when there are more |
| False authority | Wrong kind of expert |
| Bandwagon | Popular ≠ true |
| Slippery slope | Chain of inevitability without evidence |
| Begging the question | Conclusion restates the premise |
| Appeal to ignorance | No disproof ≠ proof |
| Weak analogy | The comparison doesn't hold |

AI-critique moment:

Paste this described argument into an approved chatbot and ask it to identify the fallacy: "I've been exercising every morning this month, and my grades have been great — so morning exercise must improve academic performance."
Then ask the chatbot to identify any logical fallacy. Chatbots commonly: (a) label this correctly as a false-cause fallacy, but many also conflate it with hasty generalization (wrong — the problem here is specifically sequence/causation, not overgeneralizing from too few cases); (b) offer a long explanation that sounds confident but blurs the two. Your job: evaluate whether it named the correct fallacy and whether its explanation distinguishes false cause from hasty generalization precisely. Supply the judgment it can't.

---

Segment 8 — Callback, Scope Flag & Hand-off (14 min) · Session 2 closes (~75)

Callback + tease:
- Callback: "Everything this week connects: we built a Toulmin argument in the first session, and in the second we named the twelve ways arguments collapse. A sound argument has a real claim, real evidence, and a warrant that actually links them. Every fallacy is a warrant that's missing, broken, or fake."
- Tease next week: "Week 14 — Special-Occasion & Small-Group Communication — we shift gears to a different genre: the tribute, the toast, the introduction, the acceptance speech. The persuasion principles don't go away; they just get a new occasion."

Hand-off (the week's graded work):
- Lecture Tutorial 13 (AI tutor, share-link submission) — reasoning types, Toulmin model, the twelve fallacies.
- Quiz 13 (matching item: fallacy → definition; scenario items: reasoning-type classification and fallacy identification).
- Discussion 13 — "Spot the Fallacy" applied to a described real-world argument, or "Is an emotional appeal always a fallacy?"
- Assignment 13 — fallacy identification + build-a-sound-argument (adaptive and traditional).
- Speech Workshop 13 — the spot-the-fallacy drill, build-the-Toulmin-argument, and the AI-mislabeling catch.

---

Instructor FAQ — Common Stumbles

Student says / does	Quick cure
Confuses false cause with hasty generalization.	False cause: B follows A → A caused B (wrong about causation). Hasty generalization: 2 cases → universal rule (wrong about sample size). Different structural flaws — name them precisely.
"Ad hominem just means insulting someone."	Not exactly. Ad hominem is attacking the person making the argument instead of the argument itself. A personal insult outside an argument is just rude; ad hominem is a reasoning error where the attack is offered as a reason to reject the argument.
Confuses straw man and red herring.	Straw man distorts the position and attacks the distortion. Red herring abandons the position entirely and introduces something else. One attacks (the wrong thing); the other runs away.
"All emotional appeals are manipulation."	Pathos (emotional appeal) is legitimate when the emotion is relevant and proportionate to the situation (see Week 12). It becomes manipulation — or a fallacy — when it substitutes for evidence and reasoning rather than accompanying it.
Can't find the warrant in a simple argument.	Ask: "Why does that evidence prove the claim? What principle has to be true for the evidence to be relevant?" That principle is the warrant.
Thinks begging the question just means "raising a question."	Common misuse in everyday speech, but technically it means using the conclusion as a premise — circular reasoning.

---

Scope flag

This outline teaches within Objective 7 (reasoning types, the Toulmin model, and logical fallacies) with SLO B as the primary focus (critical analysis — evaluating arguments). Stephen Toulmin is named factually as the originator of the model. All twelve fallacies are standard entries in any logic textbook and are taught as their definitions indicate — no fallacy is attributed to any political position, and all worked examples are non-partisan campus/everyday scenarios. No quotation is attributed to anyone without a verified, linked source. Persuasion ethics (the line between persuasion and manipulation) was introduced in Week 12 and recurs here via the ad hominem and emotional-appeal points.