Fallacies: D (Part 1)

Core idea

The letter D opens with a useful pause: it actually defines what a fallacy is. A fallacy is not a lie and not simply a wrong fact — it is a flaw in reasoning, a slip that anyone can make, including the honest and the clever. The surrounding entries — life in the Dead Sea, the meaning of "decimate," the many myths about deafness — show that flaw in action across nature, language and prejudice.

Why it matters

If you think a fallacy means deliberate deception, you only watch for it in opponents — never in yourself. That is the trap the logician L. Susan Stebbing warns against. A fallacy needs no disputant and no dishonesty; honesty of intention does not keep reasoning sound. The myths about deafness show the human cost: classifying deaf people as "defective" or "dumb" caused real harm, all from an unexamined chain of bad inference.

Key takeaways

Mental model

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Practical application

Audit your own reasoning, not just theirs

Because a fallacy is a reasoning slip rather than a trick, the dangerous place to look for it is your own argument. Where you feel most certain and least challenged is exactly where an unexamined inference can hide.

Separate the word from the thing

"Decimate" feels like it should mean near-total destruction because it sounds dramatic. Its Latin root means a tenth. When a word's force outruns its meaning, check the meaning. Etymology is a discipline, not a vibe — fanciful word origins are usually false.

Watch for guilt by grouping

The deaf were once filed under "insane" or "defective" in legal and census documents. The error was inference by category: lumping unlike conditions together and assuming shared traits. When a group is labelled, ask whether the label describes the people or just the filing cabinet.

Example

Someone argues that a colleague's quiet, careful manner means they lack confidence. Trace the inference: quiet, therefore unconfident. The premise does not support the conclusion — quietness can equally signal focus, or simply a different temperament. No dishonesty is involved; it is an honest leap across a missing step. That missing step is the fallacy. Naming it converts a confident judgement back into a question worth asking directly.

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