We've all heard Albert Einstein's famous line: "Insanity is doing the same thing over and over again and expecting different results."

As it turns out, insanity might be crediting that quote to Einstein over and over again. He never said it.

Misattributions like this happen pretty often. One person quotes someone else without a shoutout, and all of a sudden, they become the original speaker. Or we just decide a quote sounds like something Mark Twain would say.

These 12 surprising examples are credited to people who never really said them.

1. "Let them eat cake." — not Marie Antoinette



Not only did Marie Antoinette not utter these words, if she had, everyone probably misunderstood her.

In Jean-Jacques Rousseau's "Book 6" of his 12-volume autobiographical work, "Confessions," he writes, "At length I recollected the thoughtless saying of a great princess, who, on being informed that the countrypeople had no bread, replied, "Then let them eat pastry!" according to Phrase Finder.

Most people assume "great princess" refers to Marie Antoinette. But Rousseau wrote those words in 1767 — when Marie Antoinette was 12 years old. She also didn't marry Louis XVI until 1770.

Even if Marie Antoinette did utter the phrase, the original version in French, "Qu'ils mangent de la brioche," means "Let them eat brioche" — a type of crumbly French pastry (not unlike cake but not totally the same) eaten by the upperclass. The misinterpreted quote portrays Marie Antoinette as a callous patrician, unconcerned with the plight of the poor. But she could have meant the wealthy should stop monopolizing food and share with the lower classes — if she said it.

Other sources credit Marie-Therese, Marie Antoinette's eldest child (and the wife of Louis XIV).

2. "I disapprove of what you say, but I will defend to the death your right to say it." — not Voltaire

Voltaire didn't actually speak these words, but the idea does fall in line with his ideology.

In her well-known biography of the French philosopher, "Friends of Voltaire," Evelyn Beatrice Hall writes, "'I disapprove of what you say, but I will defend to the death your right to say it,' was his attitude now."

The author was paraphrasing how she thought Voltaire felt about a certain topic. Everyone just decided the quote was real.

3. "Standing on the shoulders of giants" — not Sir Isaac Newton

Perhaps the most well-known phrase attributed to Sir Isaac Newton, these words appeared in a letter Newton wrote to Robert Hooke, another English philosopher and mathematician. But Newton didn't coin the phrase himself. He was alluding to a simile said much earlier by Bernard of Chartres, a 12th-century man.

John of Salisbury wrote that Bernard of Chartres used to say that "we [the Moderns] are like dwarves perched on the shoulders of giants [the Ancients], and thus we are able to see more and farther than the latter."

4. "Our deepest fear is not that we are inadequate. Our deepest fear is that we are powerful beyond measure." — not Nelson Mandela



This fanciful excerpt from the former South African president's 1994 inaugural address has floated around the Internet for years. The passage goes on:

It is our light, not our darkness that most frightens us. We ask ourselves, who am I to be brilliant, gorgeous, talented, fabulous? Actually, who are you not to be? You are a child of God. Your playing small does not serve the world ... As we are liberated from our own fear, our presence automatically liberates others.

But crediting Mandela for these words right after getting out of prison seems downright ridiculous. Brian Morton puts it best in The New York Times:

"Picture it: Mr. Mandela, newly free after 27 years in prison, using his inaugural platform to inform us that we all have the right to be gorgeous, talented and fabulous, and that thinking so will liberate others," Morton writes.

In reality, self-help guru Marianne Williamson wrote these words in her 1989 spiritual best-seller, "A Return To Love." The front page of her website even boasts about the excerpt.

5. "Age is an issue of mind over matter. If you don’t mind, it doesn’t matter." — not Mark Twain/Jack Benny/Muhammad Ali

People throw this quote around all the time, accompanied by arbitrary attributions. With a little help from Quote Investigator, the problem becomes clear: No one knows who said it. The first reference found comes from an anonymous government researcher in 1968. "Aging is a matter of mind. If you don’t mind, it doesn’t matter."

Since then, the quote morphed to include "mind over matter." Comedian Jack Benny said it on his 80th birthday. A South Carolina newspaper credited Twain in 1970. And in 1981, Muhammad Ali flipped the phrase at a journalist while preparing for his last fight.

6. “Be who you are and say what you feel because those who mind don’t matter, and those who matter don’t mind.” — not Dr. Seuss

QI also debunked this famous misconception. We'd like to think Theodor Seuss Geisel, better known as Dr. Seuss, would wholly support the concept, but the reality feels a little more depressing: No evidence of the phrase exists in any of his books, and a snarky engineer coined the original.

The quote first appeared in 1938 in a London journal for municipal and county engineers. An ambiguous "Mr. Davies" directed the words toward people who criticized his housing designs.

The phrase morphed into advice about seating arrangements and a poem used in The Wall Street Journal. Dr. Seuss didn't come into play until the 2000s, mostly in high school yearbooks.

7. "Well-behaved women rarely make history." — not Marilyn Monroe

In 2007, Laurel Thatcher Ulrich, a celebrated female historian, wrote a book titled, "Well-Behaved Women Rarely Make History." Some suspect she swiped the title of her best-seller from the 1950s' favorite buxom blonde: Marilyn Monroe.

But they're wrong. Ulrich first wrote the phrase in 1976 for an issue of "American Quarterly," according to The New York Times. The original version refers to colonial woman in a very literal way. We know almost nothing about well-behaved, quiet women from that time period.

8. "There's a sucker born every minute." — not P.T. Barnum

One of Barnum's biggest competitors and critics actually said this, according to "P.T. Barnum: The Legend And The Man," a biography by A.H. Saxon.

In a 1948 article in the "Bridgeport Post," the anonymous author asked Adam Forepaugh if he could quote him on the "sucker" statement.

"Just say it's one of Barnum's slogans which I am borrowing for the occasion. It sounds more like him than it does me anyway," Forepaugh replied.

Barnum did, however, say, "The people like to be humbugged," which somehow doesn't seem as rude.

9. "If you have to ask how much they are, you can't afford one." — not J.P. Morgan

No evidence exists that Morgan actually spoke these words, typically referenced as his response to an inquiry about the price of his lavish yachts. Biographer Jean Strouse doesn't think the quote fits Morgan's language style either, according to the The Quote Verifier.

Strouse did, however, stumble upon a recording of Morgan's response to Henry Clay Pierce's question about his yacht's price. "You have no right to own a yacht if you ask that question," he said. Different words. Still uppity.

10."If you're not a liberal when you're 25, you have no heart. If you're not a conservative by the time you're 35, you have no brain." — not Winston Churchill

Churchill never said this, according to the Churchill Centre and Museum in London. In fact, Paul Addison of Edinburgh University mentions this: "Surely Churchill can't have used the words attributed to him. He'd been a Conservative at 15 and a Liberal at 35! And would he have talked so disrespectfully of Clemmie, who is generally thought to have been a lifelong Liberal?"

Instead, Francois Guizot coined the phrase in the 19th century. "Not to be a republican at 20 is proof of want of heart; to be one at 30 is proof of want of head."

11. "The ends justify the means." — not Niccolo Machiavelli

In "Heroides II," the Roman poet Ovid writes, "Exitus acta probat," which translates as "the outcome justifies the means." The closest Machiavelli comes to this idea, according to the Christian Science Monitor, occurs in "The Prince." He argues that people will always consider a prince's means as honest and praise him.

Considering he dedicated the book to the Medici family, who later arrested and tortured him, Machiavelli may have written the entire book satirically.

12. "Insanity is doing the same thing over and over again and expecting different results." — not Albert Einstein

Different versions of this quote appear everywhere (doing the same thing twice, expecting the same result, etc.), and we owe none of them to Einstein.

After Michael Becker, an editor at the Bozeman Daily Chronicle (a local paper in Montana), let the wrong version slide into an editorial, he did some research on his personal blog.

Becker traced the original back to Rita Mae Brown, the mystery novelist. In her 1983 book "Sudden Death," she attributes the quote to a fictional "Jane Fulton," writing, "Unfortunately, Susan didn’t remember what Jane Fulton once said. 'Insanity is doing the same thing over and over again, but expecting different results.'"

Now, go throw away half your coffee mugs and inspirational posters.