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Stephen Hawking famously said, ‘Intelligence is the ability to adapt to change.’ But did he really say it?

Renowned British physicist Stephen Hawking died in March at age 76. In 2016, he was onstage during the New Space Exploration Initiative “Breakthrough Starshot” Announcement at One World Observatory in New York. (Jemal Countess/Getty Images)

Look at just about any list of “best quotes” by Stephen Hawking, the brilliant theoretical physicist and cosmologist who recently passed away at the age of 76, and you will invariably find this one:

“Intelligence is the ability to adapt to change.”

It was included in a list of quotes by the British newspaper the Telegraph and by Forbes magazine, both of which said it came from his Oxford University graduation speech. It’s on the list of 10 top sayings by Hawking on and is also on a Hawking quotes list on Academic monographs have used it, unsourced.

The famed MD Anderson Cancer Center at the University of Texas used it in its 2016 annual report, without sourcing. The World Economic Forum has it on its Facebook page. And there are T-shirts for sale with the words printed on the front. Some sites, such as, source the quote to Hawking’s “A Briefer History of Time,” but it’s not in there.

I included it in a list of Hawking quotes right after he died, but then received an email from a scientist questioning whether the great scientist had ever really said or written it. I checked various sources and couldn’t find it. I called two Hawking biographers — including one who had Hawking’s support for some of her works — and they said they could not provide a source and said they did not think he said it. (I have removed the quote from that list.)

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Kitty Ferguson, an American science writer who authored the 2010 book “Stephen Hawking: An Unfettered Mind” with the scientist’s support, wrote in an email:

This sounds like something Stephen might have said, but I never heard him say it, nor have I read it in any of his own books. I have a very vague memory of seeing this attributed to someone else besides Stephen, but I can’t remember who that was or where I read it. Could it be Machiavelli?

Kristine Larsen, author of the 2007 book “Stephen Hawking: A Biography,” wrote in an email:

I am not aware of that quotation so I can’t give you any guidance on it.

As for being in his graduation speech, it is not clear that he gave one. According to the book “Stephen Hawking: A Life in Science,” the results of his final written exam at Oxford were on the border between a first- and second-class honors degree, and so he had to take an oral exam, after which he was finally given first honors.

So why does it matter? In an age in which real news is called fake and fake news is called real, it’s important that sourcing be accurate — every time. There should be no allowable slippery slope.

Though it is not certain that this quote did not come from Hawking, it is worth noting that it is not on his Wikiquote page, which has a long list of other Hawking quotes with source material for each.

Incorrectly attributed quotes are common, with one of the most famous involving Albert Einstein. He supposedly said, “If the facts don’t fit the theory, change the facts.” He didn’t — though he was commonly quoted as having said it — as you can read about here. And Aristotle apparently did not write, “Educating the mind without educating the heart is no education at all,” as has been claimed, though the Dalai Lama said something similar.

The definition of intelligence as “the ability to adapt'” appears to go back at least to 1905, with other variations explained here.

And the earliest appearance of the exact phrasing “intelligence is the ability to adapt to change” appears to be — at least online — in 1991, in a book titled “Uncommon Sense Leadership.” The earliest online source that attributes the quote to Hawking appears to be this one, from an Indonesian book, in 2009, but it doesn’t give a source.

Variations of the quote have been published for decades, such as in the 1979 book, “The Micro Millennium,” by Christopher Evans: “Intelligence is the ability of a system to adjust appropriately to a changing world.” (Page 157.)

So, if anyone out there knows for sure that Hawking said this, and can provide the source, please do.

(Correction: Earlier version referred to Hawking’s Wikipedia page. It is his Wikiquote page.)