Stephen Hawking Quotes: 19 Famous Lines and Where They Come From

Stephen Hawking on stage. © Kimberly White / Reuters

Stephen Hawking died at his home in Cambridge on 14 March 2018, aged 76. Within hours, lists of his "best quotes" were everywhere. Many of the lines in them really are his, taken from books, lectures and television interviews. Some are paraphrases that drifted over time, and at least two famous ones were never his at all.

Below are the nineteen lines that circulated most widely after his death, grouped by theme and retold in plain words, with a note on where each one comes from and how sure that attribution is. Where a line is well documented we say so; where no source has been found, we say that too.

Who Stephen Hawking was

Hawking was born in Oxford on 8 January 1942. In 1963, aged 21 and a graduate student at Cambridge, he was diagnosed with motor neurone disease, a form of ALS, and told he might have about two years to live. He lived for more than fifty years after that diagnosis.

In 1974 he proposed that black holes are not completely black but slowly give off radiation and can eventually evaporate, an idea now called Hawking radiation. He held the Lucasian Professorship of Mathematics at Cambridge from 1979 to 2009, the chair once held by Isaac Newton. His 1988 book A Brief History of Time became a worldwide bestseller, with an estimated nine million copies sold by 2009 and a record 237 weeks on the Sunday Times bestseller list. After losing his voice, he spoke through a computer, controlled first with a hand switch and later with a single cheek muscle. He was buried at Westminster Abbey.

Hawking in front of a projected galaxy at a public event. © Lucas Jackson / Reuters

On our place in the universe

1. Clever monkeys on a small planet. Perhaps the most quoted line of all begins: "We are just an advanced breed of monkeys on a minor planet of a very average star." He went on to say that our ability to understand the universe is what makes us special. It is usually cited to an interview in the German magazine Der Spiegel in October 1988; the original text has not been checked online, so treat the exact wording as likely rather than certain.

2. Aliens and Columbus. Hawking thought intelligent life elsewhere was likely, but he warned that contact could go badly for us, comparing it with Columbus reaching the Americas, which turned out badly for the people already living there. He made this point in 2010, around his Discovery Channel series Into the Universe with Stephen Hawking, and repeated it in later years.

7. The goal of a complete understanding. He described his aim as nothing less than understanding the whole universe: why it is the way it is, and why it exists at all. The line is traced to John Boslough's 1985 book Stephen Hawking's Universe.

6. Thank imperfection. His point was that small departures from perfect uniformity in the early universe allowed galaxies, stars and eventually people to form, so a mistake is not always a bad thing. The line is linked to his 2010 television series; we have not confirmed the exact episode.

16. Love, joy and beauty. Hawking argued that feelings often placed outside science can be explained by evolution. The line is widely shared under his name, but we could not trace its original source.

13. A child who never grew up. He described himself as a child who kept asking "how" and "why" questions and sometimes found an answer. This fits many things he said about curiosity, but the exact occasion is not documented in the sources we checked.

On knowledge, intelligence and free will

3. "The illusion of knowledge." The line about ignorance being a smaller enemy than the illusion of knowledge is not Hawking's. Fact-checkers trace it to the historian Daniel J. Boorstin, who used close versions in his 1983 book The Discoverers and a 1984 Washington Post interview. A newspaper first pinned it on Hawking in 2001.

9. Intelligence as adapting to change. Very popular on posters, but no source by Hawking has been found. It is best described as often attributed to him.

10. Determinism and crossing the road. His dry observation was that even people who say everything is predetermined still check for traffic. It is usually traced to his 1993 essay collection Black Holes and Baby Universes.

8. Stuck on a problem. His advice was not to get angry when stuck, but to keep the problem in mind while working on something else. He added that the black hole information question had taken him 29 years. That matches his own history: he raised the puzzle in the 1970s and changed his view in a 2004 lecture in Dublin, later calling his earlier position his "biggest blunder".

18. On boasting about IQ. Asked his IQ in a 2004 New York Times interview, he said he had no idea, adding: "People who boast about their I.Q. are losers."

14. Quiet people and loud minds. Widely shared under Hawking's name, but no book, lecture or interview has been found as its source. It should not be treated as his.

Hawking meets Pope Benedict XVI at the Vatican. © Osservatore Romano / Reuters

On disability, work and not giving up

4. Three pieces of advice. In a 2010 interview with Diane Sawyer of ABC News, he offered three rules for his children: remember to "look up at the stars and not down at your feet"; never give up work, because it gives life meaning and purpose; and if you find love, do not throw it away.

19 and 12. Be curious and do not give up. Two list entries are versions of the same message. He told an Oxford Union audience in 2016 that however hard life seems, there is always something you can do and succeed at, and that it matters not to give up. At the Sydney Opera House in 2015 he urged people to look at the stars rather than at their feet.

5. Advice to disabled people. He suggested focusing on what a disability does not stop you doing well, not regretting what it interferes with, and not letting it disable your spirit. The line comes from his interviews about living with motor neurone disease; we have not confirmed the exact first appearance.

17. Anger is a waste of time. He said there was no point being angry about his condition and that people lose patience with someone who is always complaining. The second half is cited to a Guardian interview in September 2005.

15. An active mind and humour. Hawking said that keeping his mind busy, and keeping his sense of humour, had been vital to his survival. The idea runs through his interviews and memoir, though we could not confirm the exact wording.

11. A shared human spirit. The line about different people sharing one human spirit, and adapting to survive, is commonly linked to the London 2012 Paralympics, where Hawking narrated part of the opening ceremony. We could not confirm the exact text.

Stephen Hawking at the opening ceremony of the London 2012 Paralympic Games. © Action Images / Steven Paston / Reuters

Why so many quotes get pinned on Hawking

Famous scientists attract quotes the way magnets attract iron filings. A wise-sounding line is more likely to be shared with a recognisable name attached, and Hawking, like Albert Einstein, was a natural choice: a household name, admired for his intellect and his courage. Once a line is on a poster with his photo, it can spread for years without anyone checking it.

That matters less for a harmless motto than for claims about science. A statement about black holes is something to test against evidence; a line about life is a personal view. Keeping track of who really said what lets you take both seriously.

How to check a quote before you share it

• Look for a specific source: a book with a page, a lecture with a date, or an interview with a named outlet.
• Search the phrase on fact-checking sites such as Quote Investigator, which traces many popular sayings back to their first appearance.
• Be cautious with lines that sound like modern self-help slogans; they are often much newer than the person they are pinned to.
• If you still like the line, share it as "often attributed to". That is honest, and the words can still be useful.

Hawking's real words are memorable enough on their own. Read his books, watch his lectures, and you will find plenty that he actually said.

Sources: Wikipedia: Stephen Hawking; Mimikama: the "illusion of knowledge" quote and Daniel Boorstin; Gracious Quotes: Stephen Hawking quotes with sources; CNN, 14 March 2018: Stephen Hawking quotes; Daily Maverick, 14 March 2018; photos by Kimberly White, Lucas Jackson, Osservatore Romano and Steven Paston for Reuters and Action Images.