Definition
A Logical Fallacy is a flaw in the reasoning used to connect premises to a conclusion, rendering an argument unsound. Fallacies are the “pitfalls” of human reason, often employed subconsciously to support desired conclusions.
Why It Matters
Logical fallacies are ‘bugs’ in human reasoning; failing to identify them allows flawed premises to masquerade as truth, leading to poor decision-making and the adoption of dangerous or ineffective beliefs.
Core Concepts
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Formal Fallacy: An error in the form or structure of the argument that makes it strictly invalid regardless of the content (e.g., ). The conclusion is always wrong if the logic is formal.
- How to read: “The sequence A equals B and B equals C, which implies that A is not equal to C.”
- Meaning: Invalid syllogism—transitivity of equality is violated; form alone makes the inference unsound.
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Informal Fallacy: An error in the content or context of the argument. These are “squishy” and their validity often depends on the specific situation.
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The “False Conclusion” Requirement: Every argument supporting a false conclusion must contain either a false premise or a logical fallacy.
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Metacognitive Shielding: Knowledge of common fallacies acts as an “inoculation” against deception by others and self-deception.