Employers like to put up inspirational quotes from famous people to help their team achieve greater things. At least that’s the theory. You can go online and buy a framed quote to put up in your own office: for about £30 you can get one which says “It is the people who no one imagined anything of who do the things no one can imagine.” Next to the quote is a print of Alan Turing’s signature.

Marvellous, except that – inspirational quotes for the office not being peer-reviewed publications – no source is cited. And delving around Alan Turing’s published and unpublished works doesn’t cast any light on where this one came from. That raises the slightly disturbing possibility that he didn’t say anything of the sort.

What about this other purported Alan Turing quote: “Those who can imagine anything, can create the impossible,” which features on the website of BBC Two’s Icons series. Again, a search of Alan Turing’s writings and radio speeches draws a blank. Yet this one is so snappy (especially if you remove the dubious comma) that it is found all over the place. It’s too late to stop the quote from spreading, but no one knows where it came from.

Actual Alan Turing quotes have the merit of being acidly fun, even if they are less appropriate for corporate team-building and motivational speeches. How about “No, I’m not interested in developing a powerful brain. All I’m after is just a mediocre brain, something like the President of the American Telephone and Telegraph Company.” (In the 1940s, a programmable computer was commonly referred to in the press as an ‘electronic brain’.)

Or consider “At some stage therefore we should have to expect the machines to take control.” Or even, à propos of his famous ‘Turing test’, “The original question, ‘Can machines think?’, I believe to be too meaningless to deserve discussion.” None of these three quotes is quite what you might expect, but all are authenticated. The first is from an eyewitness in the Bell Telephone Laboratories cafeteria when Alan Turing visited in 1943, the second from a radio lecture he delivered in 1951, and the third from his seminal 1950 paper ‘Computing machinery and intelligence’.

The truth is that Alan Turing didn’t write very much, or give many speeches, and what he did say was largely published in mathematical journals. Consider “Naturally one does not often wish to calculate the expression Öp(q'(t0))[b1(L1(t0))2+b2(L2(t0))2]exp[2òtt0q(z)dz], but it is valuable as justifying a common-sense point of view of the matter.” This has a hint of wryness, and some scientific significance in his 1952 paper ‘The chemical basis of morphogenesis’, but might look weird on an office wall, even in a university mathematics department. Perhaps a little touching up was needed to convince us of Alan Turing’s ability to inspire.

Enhanced reality was amply provided in the 2014 film The Imitation Game starring Benedict Cumberbatch as our quotable hero, and so not surprisingly the screenplay is a generous source of quotes. A website claiming to have the “20+ best Alan Turing quotes” leads with “Hardest time to lie to somebody is when they’re expecting to be lied to” and a bunch of other nonsense from that source, but the website has the kindness to tell us that that’s where they came from (as well as describing Alan Turing as a “fictional character”, which, in this context, may be correct). Other quote websites are less strange, but typically lead with variants of the invented “It is the people…” quote at the beginning of this article. If you study the film’s screenplay, this remark comes up a handful of times, in various forms, and it’s spoken not only by Alan Turing but by other characters as well.

If you are looking for a genuine Alan Turing quote, you might be lucky enough to have one in your pocket. The UK’s new £50 banknote, launched on 23 June 2021 on the 109th anniversary of his birth, features the quote “This is only a foretaste of what is to come and only the shadow of what is going to be.” This is from an interview that Alan Turing gave to The Times newspaper in 1949, in which he talked about the potential of an early computing machine built by his colleagues at the University of Manchester.

Perhaps none of this foray into authenticity really matters. If quotes (fake or not) invite us to consider Alan Turing’s stirring story, then that is ultimately a good thing, especially if we focus on his life, his achievements and what artificial intelligence means for the future of humanity, rather than getting distracted by retrospective Hollywood hagiography. Indeed, as someone once said, “We can only see a short distance ahead, but we can see plenty there that needs to be done.”