Logical Fallacies - Logic

🎭 What Is a Logical Fallacy?

A logical fallacy is an error in reasoning that makes an argument invalid or misleading — even when it sounds convincing at first.

Fallacies come in two broad types:

Formal fallacies — errors in the logical structure of the argument (e.g., invalid syllogisms).
Informal fallacies — errors in the content or context — what the argument is about, not just its form.

Recognizing fallacies helps you think more clearly, argue better, and avoid being deceived.

🎯 Fallacies of Relevance

These fallacies distract from the real argument by introducing something irrelevant.

👤 Ad Hominem

Attacking the person making the argument rather than the argument itself.

"You can't trust her opinion on climate change — she failed science class in 8th grade!"

🎓 Appeal to Authority

Claiming something must be true because an authority figure said so — even if they're not an expert on this topic.

"This famous actor says this vitamin cures cancer, so it must work!"

👥 Appeal to the Crowd (Ad Populum)

Arguing something must be true or good because many people believe it or do it.

"Everyone is buying this supplement — it must be effective!"

🪄 Appeal to Ignorance

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

"No one has proven ghosts don't exist, so they must be real!"

💰 Appeal to Emotion

Using strong emotional language to manipulate instead of providing evidence.

"Think of the children! We must ban all video games immediately!"

🧱 Red Herring

Introducing an irrelevant topic to distract from the actual issue.

"Why worry about school budget cuts when there are children starving in other countries?"

🔮 Fallacies of Presumption

These fallacies make hidden assumptions that haven't been established.

🌊 Slippery Slope

Claiming that one event will inevitably lead to extreme consequences through a chain of unsupported steps.

"If we allow students to redo one test, soon everyone will be demanding infinite retakes and nothing will mean anything!"

🪞 Circular Reasoning (Begging the Question)

Using the conclusion as a premise — the argument goes in a circle with no actual evidence.

"The Bible is true because it says so in the Bible." / "I'm right because I always tell the truth."

🔪 False Dichotomy (False Dilemma)

Presenting only two options when more actually exist.

"You're either with us or against us!" — ignores the possibility of neutrality or a third perspective.

⁉️ Loaded Question

Asking a question that sneaks in an unproven assumption.

"Have you stopped cheating on tests?" — assumes the person was already cheating.

🏃 Hasty Generalization

Drawing a broad conclusion from too few or unrepresentative examples.

"I met two rude people from that city — everyone there must be rude!"

🧑‍🌾 False Cause (Post Hoc)

Assuming that because A came before B, A must have caused B. (Latin: post hoc ergo propter hoc — "after this, therefore because of this")

"I wore my lucky socks and we won the game. My socks must be lucky!"

🎭 Fallacies of Weak Induction & Ambiguity

🧱 Straw Man

Misrepresenting someone's argument to make it easier to attack — arguing against a weaker or distorted version instead.

"She said we should reduce sugar in school lunches." → "So you want to ban all food and starve the kids?!"

🧓 Appeal to Tradition

Claiming something is right or good because it's always been done that way.

"We've always graded this way. Why change it now?"

🆕 Appeal to Novelty

Claiming something must be better simply because it is new.

"This is the newest version — it must be the best one!"

🎩 No True Scotsman

Protecting a generalization by dismissing any counter-example as "not a real" member of the group.

"No real scientist believes that." "But Dr. Smith does." "Then she's not a real scientist."

✏️ Practice — Identify the Fallacy (Click to Reveal)

1. "You shouldn't listen to his argument about healthy eating — he's overweight!"

Ad Hominem. The argument attacks the person's appearance rather than engaging with the actual argument about nutrition.

2. "If we allow one student to turn in homework late, soon nobody will meet any deadline ever again."

Slippery Slope. The argument assumes that allowing one exception will inevitably snowball into extreme consequences, with no evidence for each step in the chain.

3. "Nine out of ten people prefer Brand X — so it must be the best product on the market!"

Appeal to the Crowd (Ad Populum). Popularity doesn't equal quality. The majority can be wrong. (Also a potential hasty generalization if the sample was small or biased.)

4. "You're either hardworking or you're lazy — there's no in between."

False Dichotomy. Most people fall somewhere on a spectrum, or can be hardworking in some areas and less so in others. This ignores many possibilities.

5. "I started taking vitamin C tablets and three days later my cold was gone. The vitamin C cured my cold!"

False Cause (Post Hoc). The cold might have ended on its own in three days regardless — colds typically resolve in 7–10 days from onset. Correlation in timing doesn't prove causation.

6. She argued for stricter speed limits on highways. He responded: "So you want to shut down all roads and make everyone walk everywhere?"

Straw Man. He exaggerated and distorted her position (stricter limits ≠ closing all roads) to make it easier to ridicule. He never addressed her actual argument.

📋 Quick Reference Table

Fallacy	Core Error
Ad Hominem	Attack the person, not the argument
Straw Man	Distort the argument, then attack it
False Dichotomy	Only two options, when more exist
Slippery Slope	Assume extreme chain of consequences
Circular Reasoning	Conclusion is used as a premise
Appeal to Authority	Expert said it → must be true
Appeal to Crowd	Everyone believes it → must be true
Appeal to Ignorance	Not disproven → must be true
Hasty Generalization	Too few examples → broad conclusion
False Cause (Post Hoc)	A before B → A caused B
Red Herring	Irrelevant distraction
Loaded Question	Question hides an assumption

🎯 Key Takeaways

A logical fallacy is an error in reasoning that makes an argument invalid or misleading.
Ad hominem — attacks the person; straw man — attacks a distorted version of the argument.
False dichotomy — ignores options; slippery slope — assumes runaway consequences.
Post hoc — A before B doesn't mean A caused B.
Fallacies often feel convincing — learning to spot them takes practice and careful thinking.
When you find a fallacy in an argument, point out the error in logic, not in the person making it.