Widely credited to Bohr, but only secondhand. The earliest known Bohr attribution is physicist Edward Teller quoting “the dictum of Niels Bohr” in LIFE on 6 September 1954, and Teller’s wording is different: “An expert is a person who has found out by his own painful experience all the mistakes that one can make in a very narrow field.” No text by Bohr himself contains the line, and the familiar “all the mistakes that can be made” version is a later, shorter retelling (Quote Investigator ↗).
“An expert is a person who has made all the mistakes that can be made in a very narrow field” attributed to Niels Bohr. The credit is secondhand: Edward Teller quoted "the dictum of Niels Bohr" in different words in LIFE, 6 September 1954. (Quotle.info)
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In context
Evoking the world of Niels Bohr — Danish physicist, Nobel Prize in Physics 1922. Theme: "An expert is a person who has made all the mistakes that can be made in a very narrow field". Atmospheric and restrained, cinematic directional light, a muted period-appropriate palette, fine grain and texture. Compose with generous empty space for the quote and a small credit line. No lettering in the image itself.
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Minimalist editorial slide for the quote "An expert is a person who has made all the mistakes that can be made in a very narrow field". Clean background, a single muted accent color, generous negative space, subtle paper or linen texture, no literal illustration — let the words carry it. Reserve clear space for a serif quote and a small credit line. No lettering in the image itself.
Provenance
Where the line actually comes from
Earliest Bohr attribution
“Dr. Edward Teller’s Magnificent Obsession,” by Robert Coughlan, LIFE, 6 September 1954
Reported by
Edward Teller, quoting “the dictum of Niels Bohr”
In Bohr's own works
Not found. No writing, lecture or recorded remark by Bohr is known to contain it
Nearest to popular wording
Alan L. Mackay, The Harvest of a Quiet Eye (1977): “An expert is a man who has made all the mistakes, which can be made, in a very narrow field.”
But mistakes do not inhibit him. He likes to quote the dictum of Niels Bohr, the great Danish physicist, that, “An expert is a person who has found out by his own painful experience all the mistakes that one can make in a very narrow field.”
LIFE, 6 September 1954
Robert Coughlan’s profile of Edward Teller, as transcribed by Quote Investigator ↗ and listed in the sourced section of Wikiquote ↗. These are Teller’s words reporting Bohr, not Bohr’s own text, and they differ from the popular version.
1904. The idea is older than the Bohr credit. Pediatrics professor W. P. Northrup wrote in The Chicago Medical Recorder: “I’ve made all the mistakes that are possible.” The net result of that should be expert. (Quote Investigator ↗)
1954. In LIFE, Edward Teller “likes to quote the dictum of Niels Bohr”: “An expert is a person who has found out by his own painful experience all the mistakes that one can make in a very narrow field.” This is the earliest Bohr attribution known to QI. (Quote Investigator ↗; Wikiquote ↗)
1962. In The Legacy of Hiroshima, Teller (with Allen Brown) calls it “a favorite definition of Niels Bohr”: an expert is “a man who by his own painful experience has learned all the mistakes that can be committed within a narrow field.” (Quote Investigator ↗)
1977. Alan L. Mackay’s quotation anthology The Harvest of a Quiet Eye prints the shorter form under Bohr’s name and credits Teller as the source of a 1972 telling: “An expert is a man who has made all the mistakes, which can be made, in a very narrow field.” (Quote Investigator ↗)
The popular wording is not tied to any publication by Bohr, so no rights status is asserted for it. The documented forms appear in works first published in 1954 (LIFE), 1962 (Teller’s book) and 1977 (Mackay’s anthology). All of these are 1931 or later, so those specific texts should be treated as in copyright in the US.
Rights status is our research, not legal advice — and copyright varies by country and edition. For commercial or published use, confirm with the rightsholder. See terms.
Fact-check
Who gets the credit, and why
This line appears on posters and in quote apps as a clean Bohr quotation. The record is messier: the credit reaches us only through Edward Teller, the wording changed with each retelling, and the line has also been credited to Teller, to Einstein and to “Anonymous.”
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The popular wordingNiels Bohr Secondhand only
The credit is plausible, since Teller named Bohr in print during Bohr’s lifetime. But the evidence is Teller’s report, in different words, and no Bohr text contains the line (Quote Investigator ↗).
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The messengerEdward Teller Often credited directly
Teller credited Bohr in 1954 and again in 1962. Barry Popik records a 1978 Los Angeles Times interview in which Teller delivered his own version: “An expert is a person who through his own person experience has found all the mistakes one can commit in a very narrow field” (Barry Popik ↗). That retelling may explain why some collections credit Teller himself.
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A shorter variantAlbert Einstein Different wording
Reminiscences of Los Alamos 1943–1945 (1980) has “As Einstein said, ‘An expert is a person who has made every mistake once,’” according to Barry Popik ↗. No earlier source links this wording to Einstein.
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A related but different sayingWerner Heisenberg Separate quote
Heisenberg’s 1952 essay “Positivismus, Metaphysik und Religion” defines an expert as “someone who knows some of the worst mistakes that can be made in his subject, and how to avoid them.” That is a different idea, though Quote Investigator groups it in the same family of sayings (Quote Investigator ↗).
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The idea itselfW. P. Northrup Earlier
In 1904, decades before any Bohr credit, this New York pediatrician joked that he had “made all the mistakes that are possible” and so should count as expert. That is the earliest member of this family of sayings found by Quote Investigator ↗.
✓The best evidence is Teller’s word: he credited Bohr in LIFE in 1954 and in 1962 called it “a favorite definition of Niels Bohr.” The neat “all the mistakes that can be made in a very narrow field” wording is a later polish, and the idea itself was in print by 1904 (Quote Investigator ↗).
Context
Why Teller kept repeating it
Edward Teller used Bohr’s definition to defend trial and error in weapons research. In LIFE’s 1954 profile it explains why “mistakes do not inhibit him.” In The Legacy of Hiroshima (1962), he applied it to the Livermore laboratory after its early failures.
That telling is the earliest source in which the saying does real work, and it suggests why the line survived. Teller presented it as earned humility: expertise is the scar tissue of failures, and it covers a narrow field, not everything.
We at Livermore had made all the mistakes that seemed possible. We now were experts.
Teller's 1962 passage in full
“Back at Livermore, we started again. But our efforts this time were led by a group of real experts. An expert, according to a favorite definition of Niels Bohr, is a man who by his own painful experience has learned all the mistakes that can be committed within a narrow field. We at Livermore had made all the mistakes that seemed possible. We now were experts, and each year from 1955 to 1958 the laboratory brought in a rich harvest of unexpected and practical results.” — Edward Teller with Allen Brown, The Legacy of Hiroshima (1962), as transcribed by Quote Investigator ↗.
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Filed under
More provenance-checked quotes on the same theme, each with its reuse status.
1885–1962 · Danish physicist, Nobel Prize in Physics 1922
Niels Henrik David Bohr was a Danish theoretical physicist who laid foundations for our understanding of atomic structure and quantum theory. He received the 1922 Nobel Prize in Physics “for his services in the investigation of the structure of atoms and of the radiation emanating from them.” His dry remarks were often repeated by colleagues, which is how this definition of an expert reached print: through Edward Teller, not through Bohr’s own writing.
For writers & researchers
Cite this
Cite this
Earliest known Bohr attribution: Robert Coughlan, “Dr. Edward Teller’s Magnificent Obsession,” LIFE, September 6, 1954, 62 (Edward Teller quoting Bohr, in different wording). Documented in Quote Investigator, “An Expert Is a Person Who Has Made All the Mistakes Which Can Be Made in a Very Narrow Field,” January 15, 2023, https://quoteinvestigator.com/2023/01/15/expert-mistakes/.
This verification page
Quotle.info. “Who really said ‘An expert is a person who has made all the mistakes that can be made in a very narrow field’?” Last verified 3 Nov 2026. https://quotle.info/who-said/an-expert-is-a-person-who-has-made-all-the-mistakes-that/