Don't Judge a Book by Its Cover
Surface appearance is a bad guide to substance — the modern anti-prejudice proverb every middle-school assembly is built on.
Origin
Surprisingly recent: not recorded in English before the mid-19th century. The first clear printed use is in *American Speech* in 1929 ('You can't judge a book by its binding'); George Eliot's *The Mill on the Floss* paraphrased the thought, and 20th-century children's literature picked it up. By the 1960s it was the standard anti-prejudice proverb taught to American schoolchildren.
Modern usage
Reflexive comeback against snap judgments about looks, dress, accent, neighborhood, or résumé. Foundational in DEI training, kids' picture books, makeover-show voiceovers, and dating advice. A modern stand-in for the older [[all-that-glitters-is-not-gold]], which warns in the opposite direction.
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