Lecture 5.2: Fallacies and Faulty Reasoning — Lecture Series 5: Communication in English

Section III

The Ten Major Fallacies — Full Analysis

The following ten fallacies are among the most commonly encountered in academic writing, political discourse, everyday conversation, and the media. Each is presented with a full definition, a clear Nigerian or academic example, a logical analysis of exactly why it fails, and guidance on how to avoid it in your own arguments (Engel, 2020, p. 20).

✖ Fallacy 1 — Ad Hominem (Attack on the Person)

Latin: "Against the Person"

Definition: The ad hominem fallacy occurs when someone attacks or dismisses an argument by criticising the person making it rather than addressing the argument itself. Instead of engaging with the evidence or reasoning provided, the attacker redirects attention to the character, motives, personal history, or circumstances of the speaker. The Latin name means "against the person" (Hurley & Watson, 2018, p. 128).

Example 1 — Political Context

"Senator Adamu has proposed a new policy to reduce poverty through agricultural subsidies. But why should we listen to him? He has been accused of financial misconduct and he himself comes from a wealthy family that has never experienced poverty."

Why it is a fallacy: The argument does not address a single aspect of the agricultural subsidy proposal. It attacks the senator's personal history and background instead. Even if the senator is wealthy or has faced accusations, those facts are irrelevant to whether the policy would actually reduce poverty. The policy must be evaluated on its own merits — its economic logic, its evidence base, its implementation feasibility — not on the character of the person proposing it. The senator's biography cannot make a good policy bad or a bad policy good.

Example 2 — Academic Context

"Dr. Eze argues that the university's new examination policy is unfair to students. But everyone knows she has a conflict with the Dean, so of course she would say that."

Why it is a fallacy: Even if Dr. Eze has a personal conflict with the Dean, that fact does not address the substance of her argument about the examination policy. Her motives for making the argument are entirely separate from whether her argument is correct. Even people with personal grievances can make valid arguments — and even people with no apparent motivation can make poor ones. The argument about the policy must stand or fall on its own logical and evidential merits.

Varieties of Ad Hominem

There are three common forms: (1) Abusive Ad Hominem — directly insulting the person (calling them stupid, corrupt, or dishonest). (2) Circumstantial Ad Hominem — claiming the person's argument is biased because of their circumstances or self-interest (as in the Dean example). (3) Tu Quoque (You Too) — dismissing a person's argument by pointing out that they themselves do not follow the principle they are advocating. Example: "You tell me to exercise regularly, but you never exercise yourself!" — even if true, this does not disprove the health benefits of exercise (Walton, 2020, p. 34).

How to Avoid It in Academic Writing

Rule: Always address the argument, not the person making it. In academic writing, you engage with the ideas, evidence, and reasoning in a text — never with the personality, reputation, or personal history of the author. If you disagree with a scholar, show specifically why their evidence is insufficient, their reasoning flawed, or their conclusions overstated. Personal characteristics are simply irrelevant to academic evaluation of arguments.

✖ Fallacy 2 — Straw Man

Misrepresentation Fallacy

Definition: The straw man fallacy occurs when someone misrepresents, distorts, or exaggerates an opponent's argument to make it easier to refute — and then attacks the distorted version rather than the actual argument. The name comes from the idea of constructing a "straw man" (a flimsy imitation) and then knocking it down instead of engaging with the real, stronger opponent (Engel, 2020, p. 54).

Example 1 — Education Policy Debate

Person A: "I think students should have some voice in how assessment methods are designed at our university." Person B: "So you're saying students should just grade themselves and do whatever they want? That would make a mockery of academic standards."

Why it is a fallacy: Person A said nothing about students grading themselves or abandoning academic standards. They only suggested that students should have some voice in how assessment methods are designed — a reasonable request that many universities accommodate through student representation. Person B has created a wild distortion of Person A's actual position, made it look extreme and absurd, and then attacked that distortion. Person A's actual argument has not been engaged with at all. This is the straw man: attack what was never said.

Example 2 — Political Discourse

Activist: "The government should reduce expenditure on arms and redirect some of those funds toward healthcare." Opponent: "These people want Nigeria to have no defence at all — they want our enemies to walk in and take over the country!"

Why it is a fallacy: The activist proposed reducing some arms spending and redirecting it to healthcare — not abolishing Nigeria's entire defence capability. "Reducing expenditure" is dramatically different from "having no defence at all." The opponent has grossly distorted the position to make it sound treasonous, then attacked the distortion. Every debate, essay, and conversation requires engaging with what someone actually said — not a cartoon version of it (Walton, 2020, p. 40).

How to Avoid It in Academic Writing

Rule: When discussing an author's argument, always represent it as accurately and charitably as possible — present the strongest version of the opposing view before engaging with it. This is called the principle of charity. Read directly from the source. Quote precisely. If you disagree, engage with the actual argument, not a weakened version of it. Writing that misrepresents other scholars damages your academic credibility and is a form of intellectual dishonesty.

✖ Fallacy 3 — False Dichotomy (Either/Or Fallacy)

Also: False Dilemma, Black-and-White Thinking

Definition: The false dichotomy fallacy (also called the false dilemma) occurs when an argument presents only two options as if they were the only possibilities, when in reality there are additional options that have been ignored or suppressed. It forces an artificial binary choice between two extremes, eliminating the middle ground (Copi et al., 2019, p. 178).

Example 1 — Academic Debate

"You either fully support our university's new examination policy or you are against academic excellence. Which is it?"

Why it is a fallacy: This presents only two positions: full support for the policy, or opposition to academic excellence. But there are many other possibilities: a person could support academic excellence while believing this particular policy is a poor way to achieve it. A person could support excellence while also wanting the policy revised, modified, partially implemented, or replaced with a better alternative. The argument eliminates all middle ground and nuance to force agreement through a false choice.

Example 2 — Nigerian Political Discourse

"If you do not vote for our party in the next election, then you want Nigeria to collapse. There is no middle ground."

Why it is a fallacy: This ignores the full spectrum of political choices: voting for a different party, voting for an independent candidate, advocating for electoral reform, supporting civil society oversight, or believing that a different solution entirely is needed. The argument illegitimately collapses all of these options into one: vote for us, or the country collapses. Real-world situations almost always have more than two options (Bassham et al., 2020, p. 160).

How to Avoid It in Academic Writing

Rule: Before constructing any argument that says "either X or Y," ask yourself: are these genuinely the only two options? In almost every academic debate, there is a spectrum of positions. Acknowledge the full range of views. If you are presenting a binary, make sure it is genuinely exhaustive — that you have demonstrated there truly are no other alternatives before forcing a choice.

✖ Fallacy 4 — Hasty Generalisation

Also: Sweeping Generalisation, Overgeneralisation

Definition: A hasty generalisation occurs when a broad general conclusion is drawn from a sample that is too small, too limited, or unrepresentative of the population being described. The arguer sees a few examples and incorrectly concludes that those examples represent the whole (Hurley & Watson, 2018, p. 152).

Example 1 — Everyday Student Context

"I met three students from Department X and all three were arrogant and unfriendly. The students in that department are clearly arrogant and unfriendly people."

Why it is a fallacy: Three individuals cannot represent an entire department of potentially hundreds of students. The three students encountered may have been having bad days, may be atypical of their peers, or may have been selected by chance from a narrow social circle. The conclusion — that all students in the department share these qualities — goes dramatically beyond what three encounters can establish. This is the essential error of the hasty generalisation: the evidence is too small and potentially unrepresentative to support the broad conclusion drawn.

Example 2 — Research and Academic Writing

"A study of 15 students in one classroom found that those who studied with background music performed better on a quiz. Therefore, listening to music while studying improves academic performance."

Why it is a fallacy: Fifteen students in one classroom is far too small a sample to generalise to all students. The students may share unique characteristics (all music lovers, all habitual background-noise studiers, all studying the same easy material). The results may not replicate across different subjects, ages, music types, or study conditions. Academic research requires large, diverse, representative samples before such generalisations can be made. This is why peer-reviewed studies go through rigorous methodology review (Govier, 2020, p. 105).

How to Avoid It in Academic Writing

Rule: Never draw conclusions that outrun your evidence. If you have two or three examples, your conclusion should be hedged: "This suggests...", "It appears that...", "In some cases..." Do not write "This proves that all..." or "This shows that every..." unless your evidence is comprehensive and representative. Academic writing demands proportionate claims: strong evidence justifies strong conclusions; limited evidence justifies tentative conclusions only.

✖ Fallacy 5 — Appeal to Inappropriate Authority

Latin: Ad Verecundiam

Definition: This fallacy occurs when an argument cites an authority figure as evidence for a claim, but that authority is not actually an expert in the relevant field, or when authority is invoked to settle a question that legitimate experts disagree about. Note that citing genuine experts is not a fallacy — the fallacy arises only when the authority cited is inappropriate, biased, or cited as if they settle a genuine debate (Engel, 2020, p. 68).

Example 1 — Celebrity Endorsement

"A popular Nollywood actor says this herbal supplement cures high blood pressure. It must work — he's a very successful person."

Why it is a fallacy: The actor's success in the film industry gives them no expertise whatsoever in pharmacology, medicine, or human physiology. A celebrity's popularity does not confer scientific knowledge. The claim about the herbal supplement must be evaluated through clinical trials, peer-reviewed medical research, and assessment by qualified physicians — not through the endorsement of a famous face. Advertising routinely exploits this fallacy because celebrity association is psychologically persuasive even when logically irrelevant.

Example 2 — Academic Context

"Professor Nwosu, a respected economist, has said that climate change is exaggerated. Therefore, we can disregard the scientific consensus on global warming."

Why it is a fallacy: Professor Nwosu's expertise is in economics, not climate science. Even if he is an excellent economist, his opinion on climate science carries no special authority beyond that of any educated layperson. Furthermore, the scientific consensus on climate change is established by tens of thousands of climate scientists worldwide — the opinion of one economist in a different field cannot outweigh that body of evidence. Genuine appeal to authority requires citing experts who are genuinely expert in the relevant field, where a clear consensus exists (Bassham et al., 2020, p. 168).

How to Avoid It in Academic Writing

Rule: When citing authorities, ensure they are genuine experts in the specific field being discussed. Check that the majority of experts in that field hold the same view. Never use a single expert opinion to dismiss a well-established consensus. Always distinguish between fields — a great engineer's opinion on economics is just an informed opinion, not expert testimony. In academic writing, rely on peer-reviewed sources in the relevant discipline.

✖ Fallacy 6 — Slippery Slope

Also: Camel's Nose, Domino Fallacy

Definition: The slippery slope fallacy occurs when an argument asserts that one event will inevitably lead to a chain of increasingly extreme and undesirable consequences, without providing adequate evidence for each step in that chain. It assumes, without justification, that a moderate first step will necessarily lead to catastrophic final outcomes (Walton, 2020, p. 58).

Example 1 — University Policy

"If we allow students to submit assignments one day late without penalty, next they will want a week's extension. Then they will want to write examinations at home. Eventually, students will stop attending lectures altogether, and academic standards will collapse completely."

Why it is a fallacy: The argument assumes that each step in this chain will inevitably follow from the previous one, but it provides no evidence for these causal links. A one-day grace period does not logically or necessarily lead to home examinations or abandoned lectures. Each step in the chain would require a separate decision, separate policy, and separate circumstances — none of which are established by the first step. The argument uses fear of an imagined worst case to oppose a reasonable and modest proposal.

Example 2 — Social Policy

"If Nigeria legalises same-sex civil partnerships, next people will want to marry animals, then children. Our entire moral and social structure will disintegrate within a generation."

Why it is a fallacy: The argument leaps from one specific legal change to a series of increasingly extreme and logically disconnected outcomes. The argument provides no evidence whatsoever for why civil partnership legislation would lead to marriages with animals or children — claims that involve entirely different legal, ethical, and biological categories. Countries that have changed partnership laws have not experienced these predicted consequences. The fallacy manufactures fear through an unjustified chain of "what if" scenarios (Copi et al., 2019, p. 182).

How to Avoid It in Academic Writing

Rule: If you argue that one thing will lead to another, you must provide specific evidence for each causal link in the chain. Do not assume that the first step makes later steps inevitable. Acknowledge that intervening decisions, safeguards, or circumstances exist that could stop the chain at any point. Legitimate slippery slope arguments do exist — but only when each causal step is individually evidenced and justified.

✖ Fallacy 7 — Circular Reasoning (Begging the Question)

Latin: Petitio Principii

Definition: Circular reasoning, or begging the question, occurs when the conclusion of an argument is used as one of its premises — either explicitly or in a disguised form. The argument goes in a circle: it assumes as true the very thing it is trying to prove, providing no real evidence or reasoning beyond restating the conclusion (Hurley & Watson, 2018, p. 160).

Example 1 — Simple and Clear

"The Bible is the word of God because the Bible says it is the word of God."

Why it is a fallacy: The argument is perfectly circular. The premise (the Bible says it is God's word) and the conclusion (the Bible is God's word) are logically identical. To use a document to prove its own divine authority is to assume what you are trying to establish. For someone who already accepts the Bible's authority, no argument is needed. For someone who doesn't, this argument provides nothing they would accept as evidence. A genuine argument for biblical authority would need to draw on external historical, archaeological, or philosophical evidence.

Example 2 — Academic and Institutional Context

"This textbook must be reliable because it says in the preface that it is a reliable and authoritative source on the subject."

Why it is a fallacy: A book's claim about its own reliability is not evidence of its reliability. The same reasoning could be applied to any book, reliable or not. Reliability must be established by external criteria: the credentials of the author, the rigour of the research methodology, the accuracy of claims when checked against independent sources, peer review, and citation in other credible scholarship. A book does not become reliable merely by claiming to be so (Govier, 2020, p. 116).

Disguised Circular Reasoning

Circular reasoning is often harder to detect when the premise and conclusion are worded differently. Example: "Wealthy people deserve their success because successful people have always worked hard and earned what they have." This uses "deserve success" and "earned what they have" as if they are different, but they are the same claim rephrased. The argument is: wealthy people deserve success because wealthy people deserve success.

How to Avoid It in Academic Writing

Rule: Never use a claim as evidence for itself, even when the two are phrased differently. Your premises must be logically distinct from and genuinely supportive of your conclusion. If you find yourself writing a paragraph that seems to simply restate the thesis in different words without providing new evidence or reasoning, you are likely engaging in circular reasoning. Each body paragraph must add something genuinely new to the argument.

✖ Fallacy 8 — Red Herring

Also: Ignoratio Elenchi, Missing the Point

Definition: The red herring fallacy occurs when an argument introduces an irrelevant topic or piece of information to distract the audience from the actual issue being discussed. Rather than engaging with the real argument, the speaker or writer redirects attention to something tangentially related but logically irrelevant — deliberately or accidentally steering the discussion off course (Engel, 2020, p. 86).

Example 1 — Political Accountability

Journalist: "Your government has not built any new schools despite promises to improve education. How do you respond?" Politician: "I am glad you raised the topic of education. Education is close to my heart. In fact, I was the first person in my family to attend university, and that experience shaped everything I care about in public service. Let me tell you about my humble beginnings..."

Why it is a fallacy: The journalist asked a direct, specific question about unfulfilled school construction promises. The politician responded with an emotional personal story about their own education — which is entirely irrelevant to whether schools were built as promised. The personal story may be true and touching, but it does not address the accountability question at all. The politician has introduced a red herring: a sympathetic distraction designed to change the emotional atmosphere and avoid the uncomfortable question entirely.

Example 2 — University Life

Student: "The grading for this assignment seems inconsistent. I answered the same questions as my classmate and received a much lower mark." Lecturer: "You know, what concerns me more is your attendance record this semester. You missed three lectures in October."

Why it is a fallacy: The student raised a specific, legitimate concern about the consistency of grading. The lecturer responded by raising a completely separate issue — attendance — which is irrelevant to whether the grading of this particular assignment was fair. Even if the student's attendance was poor, that does not address or resolve the question of grading consistency. The attendance issue is a red herring: it may be a valid concern in its own right, but it belongs in a separate conversation (Walton, 2020, p. 64).

How to Avoid It in Academic Writing

Rule: Every paragraph and every sentence in an academic essay must be relevant to the thesis. Before including any piece of information, ask: does this directly support my argument, or does it merely surround it? Red herrings often appear when a writer is unsure how to support a claim and instead writes around it. Discipline yourself to eliminate anything that does not directly advance the argument you are making.

✖ Fallacy 9 — Post Hoc Ergo Propter Hoc

Latin: "After this, therefore because of this"

Definition: The post hoc fallacy occurs when someone concludes that because Event B followed Event A in time, Event A must have caused Event B. It confuses correlation (two things happening together or in sequence) with causation (one thing actually causing the other). The full Latin phrase is Post hoc ergo propter hoc — "after this, therefore because of this" (Copi et al., 2019, p. 186).

Example 1 — Superstition and Daily Life

"I wore my blue shirt on the day of my examination and I scored 90%. I will always wear my blue shirt for examinations because it brings me good results."

Why it is a fallacy: The score of 90% followed the wearing of the blue shirt in time, but there is no causal mechanism by which a shirt's colour could affect examination performance. The actual causes of the good result are almost certainly the student's preparation, the difficulty level of the paper, their mental state on that day, and their understanding of the subject matter. The blue shirt happened to be present when these conditions were satisfied — but "present at the same time as" is radically different from "the cause of." This is also the basis of most superstitious beliefs worldwide.

Example 2 — Economic and Political Reasoning

"The economy improved significantly in the two years after Governor Adebayo took office. Therefore, Governor Adebayo's policies are responsible for the economic improvement."

Why it is a fallacy: Economic improvements that follow a governor's assumption of office may be caused by many factors unrelated to their policies: global oil price increases, rainfall patterns that improved agriculture, policies inherited from the previous administration finally taking effect, international investment decisions made years earlier, or simple economic cycles. To attribute the improvement to the current governor's policies without isolating their specific contribution and excluding other explanations is to commit the post hoc fallacy. In social research, establishing causation requires controlled analysis — not mere temporal sequence (Bassham et al., 2020, p. 172).

How to Avoid It in Academic Writing

Rule: Never write "because A happened before B, A caused B." To claim causation in academic writing, you must: (1) establish that A preceded B, (2) show that A and B are correlated, (3) provide a plausible causal mechanism, and (4) eliminate alternative explanations. The words "correlation," "associated with," and "may have contributed to" are appropriate when you can show a relationship but cannot establish full causation. The words "caused" and "led to" require much stronger evidence.

✖ Fallacy 10 — Bandwagon / Ad Populum

Latin: "Appeal to the People"

Definition: The bandwagon fallacy (formally called ad populum, meaning "appeal to the people") occurs when an argument claims that something must be true, good, or right simply because many people believe it or do it. The popularity of a belief is offered as if it were evidence for its truth or value (Hurley & Watson, 2018, p. 168).

Example 1 — Consumer Behaviour

"Over 10 million Nigerians use Miracle Herb Supplement every day. It must be effective. Join the millions who have already discovered the secret!"

Why it is a fallacy: The number of people using a product tells us absolutely nothing about whether it works. Ten million people could be buying a supplement that has no pharmacological effect whatsoever, perhaps because its advertising is compelling, because it was endorsed by a celebrity, or because social pressure makes it fashionable. Historically, millions of people have simultaneously believed in things that turned out to be false or harmful. Truth and effectiveness are not determined by headcount. The supplement's effectiveness must be established by clinical trials, not by sales figures.

Example 2 — Academic and Social Pressure

"Everyone in this department knows that Professor X's grading is unfair. Since everyone thinks so, it must be true."

Why it is a fallacy: Even if every student in the department holds this belief, the truth of the claim must be established by examining actual grading evidence — comparing marked scripts against the marking scheme, analysing grade distributions, reviewing moderation procedures. Widespread belief among those who may have an interest in perceiving unfairness (students who received low grades) is not objective evidence. Throughout history, entire populations have simultaneously held beliefs that were demonstrably false (Engel, 2020, p. 98).

Why Bandwagon Is So Common

Humans are social animals with a deep evolutionary tendency to conform to group behaviour. The bandwagon fallacy exploits this psychological tendency. Phrases like "everyone knows that...", "it is widely accepted that...", "most people believe...", "the majority agrees..." are often signals that a bandwagon argument is being made. In academic contexts, you may cite a consensus among experts in a field — but this is different from citing popular opinion or majority belief among the general public.

How to Avoid It in Academic Writing

Rule: Never use "everyone believes" or "most people think" as evidence for a factual claim. Evidence must be evaluated on its own merits, not on the number of believers. When citing consensus, ensure it is a consensus among relevant experts in the relevant field, not general public opinion. And always remember: once, the entire world believed the earth was flat. Popularity has never been a reliable guide to truth.

Lecture Series 5: Communication in English

Fallacies and Faulty Reasoning

What Is a Logical Fallacy?

Formal vs. Informal Fallacies

The Ten Major Fallacies — Full Analysis

Practical Activity — Fallacy Identification

Key Takeaway

Examination Questions

References

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