The proverb warns against forming a judgement on outward appearance alone. A shabby exterior may hide something valuable, and a handsome one may hide nothing much at all, so the sensible course is to look past the surface before deciding what a person or a thing is worth. Though the image is drawn from books, the saying is almost always applied to people.
What’s the origin of the phrase ‘don’t judge a book by its cover’?
The sentiment is old, but the familiar wording is more traceable than many suppose, and it is American rather than modern. The idea of not judging a book by its outside runs through English-language newspapers from the early nineteenth century onward. A piece in the Boston Daily Advertiser of 29 August 1821 already speaks of “a man who judges of a book by its outside show,” and similar turns of phrase appear repeatedly over the following decades in variant forms: by a book’s title, its size, its covering, its weight.
The exact modern shape arrives by the middle of the century. On 12 June 1849 the Boston Daily Mail ran the headline “Don’t Judge a Book by its Cover,” which is the wording still in use today. Five years later, on 22 July 1854, The Citizen already treated it as established, calling it “an old proverb, that we must not be led away by appearance, and that we must never judge a book by its cover.” That a newspaper of 1854 could describe it as old tells us the expression was in common speech well before it was written down in this form.
A frequently cited literary source is George Eliot’s novel The Mill on the Floss, published in 1860. The book contains a closely related thought rather than the proverb itself. Mr Tulliver, having bought a job lot of uniformly bound volumes at a sale and finding one of them unsuitable, remarks that they were “all bound alike, it’s a good binding, you see, and I thought they’d be all good books.” He then concludes: “But it seems one mustn’t judge by th’ outside. This is a puzzlin’ world.” This is the same lesson, but it is not a statement of the fixed proverb, and it postdates the 1849 headline by more than a decade.
The saying kept its currency into the twentieth century. It surfaces, for instance, in the 1946 American mystery novel Murder in the Glass Room by Edwin Rolfe and Lester Fuller, in the form “You can never tell a book by its cover,” one of several wordings that have circulated alongside the standard one. The thought has older companions in English: ‘all that glitters is not gold’ warns against the attractive surface, and ‘a leopard cannot change its spots’ against expecting the inside to change.