In 1480, Dutch milkmaids pulled a mermaid from the mud of a flooded meadow. They dressed her in woman’s apparel and taught her to spin wool, yet she never spoke or laughed. This 1880 survey of mermaid accounts across five centuries is not quite folklore and not quite debunking. It is something harder to name: a record of what people needed to believe, and how stubbornly that need survived the evidence against it.