Fallacies: G (Part 2 of 2)

Core idea

The back half of letter G is a collection of confident-sounding "facts" that crumble on inspection. Glass does not flow; gold cannot be grown; gravity is not a simple pull; the Great Dane is not Danish; gum does not linger in your gut for seven years. Most of these survive because each carries a small piece of plausible reasoning — and a half-true premise is far more durable than a wholly false one.

Why it matters

Half-truths are the hardest myths to kill. "Old cathedral glass is thicker at the bottom" is true; the inference that it flowed downhill is false. "Alchemists discovered real chemistry" is true; the idea that they could transmute lead to gold is not. Learning to split a claim into its true and false halves is the most useful single move in this topic — it protects you from believing a falsehood just because it travels with a fact.

Why the myths persist

A true observation carries a false explanation

Antique window panes really are thicker at one edge — because they were made and hung that way, not because glass crept downward over centuries. The observation is sound; the story attached to it is invented.

The name points the wrong way

The Great Dane was bred in Germany and known for centuries as the Deutsche Dogge. The English name simply mislabels it, and the label then teaches everyone the wrong origin.

An old authority lends false weight

"Aurum vegetabile" — growable gold — was repeated for centuries because learned books said so. Repetition by authorities, not evidence, kept it alive.

Key takeaways

Mental model

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Practical application

When a claim sounds authoritative, split it before you accept or reject it:

1. Isolate the observation from the inference. "Old glass is thicker at the bottom" — keep that, it is verified. "Therefore glass flows" — test that separately; it fails.
2. Distrust names as evidence of origin. A "Great Dane" or a "hamburger" tells you what people called a thing, not where it came from.
3. Discount authority used in place of data. Centuries of scholars endorsed growable gold. Count it as one repeated rumour, not many proofs.
4. Ask whether a feature still has a function. Goosebumps once insulated fur; in a hairless human they do nothing. A trait that worked for an ancestor need not work for you.

Example

A home-renovation video claims your sash windows are "warping because glass slowly melts." Split the claim. Observation: the lower edge of each pane is measurably thicker — verified, you can feel it. Inference: the glass melted downward — test it. If glass flowed at room temperature, far older Roman glass vessels would have puddled long ago; they have not. The thickness comes from the eighteenth-century crown-glass process, which produced uneven sheets hung heavy-edge-down. You keep the true half (uneven panes), discard the false half (flowing glass), and save yourself an unnecessary repair.

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