What Is a Logical Fallacy?
A logical fallacy is a flaw in reasoning that renders an argument invalid or unsound — even when the conclusion sounds persuasive. Fallacies appear everywhere: political speeches, advertising, social media debates, and everyday conversation. Learning to recognize them is one of the most practical skills philosophy offers.
Fallacies are typically divided into formal fallacies (errors in the logical structure of an argument) and informal fallacies (errors in the content or context of reasoning). The twelve below are predominantly informal — the kind you encounter most in everyday argumentation.
The 12 Fallacies
1. Ad Hominem
Attacking the person making an argument rather than addressing the argument itself. "You can't trust his views on climate policy — he failed chemistry." The speaker's personal qualities are irrelevant to whether the argument is logically valid.
2. Straw Man
Misrepresenting someone's position in a weaker or more extreme form in order to refute it more easily. "She wants stricter gun laws, so she wants to ban all guns." Refuting the exaggerated version leaves the actual argument untouched.
3. False Dilemma (Either/Or)
Presenting only two options when more exist. "You're either with us or against us." Real situations almost always contain more possibilities than a binary framing allows.
4. Slippery Slope
Arguing that one small step will inevitably lead to extreme consequences, without evidence for each causal link. "If we allow assisted dying, soon we'll be euthanizing anyone inconvenient."
5. Appeal to Authority (Argumentum ad Verecundiam)
Claiming something is true because an authority figure said so — particularly when that authority lacks relevant expertise. Legitimate appeals to expertise are valid; appeals to celebrity or irrelevant authority are not.
6. Circular Reasoning (Begging the Question)
Using the conclusion as a premise in the argument. "The Bible is true because it is the word of God, and we know it is the word of God because the Bible says so." The argument provides no independent support for its conclusion.
7. Hasty Generalization
Drawing a broad conclusion from a small or unrepresentative sample. "I met two rude people from that city — everyone there must be unfriendly."
8. Post Hoc Ergo Propter Hoc
Assuming that because B followed A, A caused B. "I wore my lucky socks and we won the game — the socks are lucky." Correlation is not causation.
9. Appeal to Popularity (Ad Populum)
Arguing that something is true or good because many people believe it. History is full of widely held beliefs that turned out to be wrong.
10. Red Herring
Introducing an irrelevant point to divert attention from the actual issue. A skilled debater can disguise a red herring as a substantive response.
11. False Equivalence
Treating two things as equivalent when they differ in morally or logically significant ways. "Both sides have done bad things" — used to dismiss genuinely asymmetric situations.
12. Appeal to Nature
Assuming that what is "natural" is inherently good or correct. Many natural things are harmful; many artificial things are beneficial. The natural/unnatural distinction carries no automatic moral weight.
A Quick Reference Table
| Fallacy | Core Error |
|---|---|
| Ad Hominem | Attacking the person, not the argument |
| Straw Man | Misrepresenting the opposing view |
| False Dilemma | Ignoring middle-ground options |
| Slippery Slope | Unsupported chain of consequences |
| Appeal to Authority | Irrelevant or misplaced expertise |
| Circular Reasoning | Conclusion assumed in premise |
| Hasty Generalization | Too small a sample |
| Post Hoc | Correlation mistaken for causation |
| Appeal to Popularity | Majority belief ≠ truth |
| Red Herring | Irrelevant distraction |
| False Equivalence | Ignoring meaningful differences |
| Appeal to Nature | "Natural" doesn't mean good |
How to Use This Knowledge
Recognizing fallacies is not merely a debating trick. It is an exercise in intellectual honesty — including toward your own reasoning. The next time you feel strongly persuaded by an argument, ask: is the logic actually sound, or is something else doing the persuasive work? That pause is the beginning of genuine critical thinking.