The idea is well documented as Bohr’s own: Abraham Pais, who worked with him, wrote in 1967 of “Bohr’s precept never to speak more clearly than one thinks,” and other writers quote him in the first person (“I try not to speak more clearly than I think”). But no primary source contains this exact “express yourself” wording. It is a later quotation-book version of the saying.
“Never express yourself more clearly than you are able to think” Attributed to Niels Bohr — the idea is his (Abraham Pais, 1967, describes “Bohr’s precept never to speak more clearly than one thinks”), but the popular wording “Never express yourself more clearly than you are able to think” has no primary source. Via Quotle.info
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Provenance
The closest documented source
Witness
Abraham Pais, “Reminiscences from the Postwar Years”
First published in
Niels Bohr: His Life and Work as Seen by His Friends and Colleagues
Edition
Stefan Rozental, ed. · North-Holland, Amsterdam, 1967; reprinted in Niels Bohr: A Centenary Volume (Harvard University Press, 1985)
Popular wording
No primary source located
Bohr was divinely bad as a public speaker. This was not due to his precept never to speak more clearly than one thinks. Had he done so, the outcome would have been quite different, as Bohr was a man of the greatest lucidity of thought.
Pais on Bohr
Text as reprinted in Niels Bohr: A Centenary Volume (1985). The 1967 original reads “Bohr’s precept.” This is Pais describing Bohr’s saying, not the popular wording.
Wikiquote lists the popular wording among Bohr’s quotes, but its only citation is a 2004 compilation, Jason Merchey’s Values of the Wise, p. 63 (Wikiquote ↗). Quote Investigator has no entry for this quote.
Abraham Pais’s 1967 reminiscence in Stefan Rozental’s volume describes “Bohr’s precept never to speak more clearly than one thinks” (Open Library full-text search ↗).
First-person versions are quoted by Lincoln Barnett (1964), Ruth Moore (1966) and Richard Rhodes, all with “speak more clearly than I think” (Open Library full-text search ↗).
The “express yourself … are able to think” wording shows up in quotation books, not in writing by Bohr or people who knew him (Open Library full-text search ↗).
The exact popular wording has no identifiable source, so we make no copyright claim for it. The documented versions appear in works first published from 1964 onward (Barnett 1964, Moore 1966, Pais 1967, Rhodes 1986). All of those are after 1931, so they are presumably still in copyright.
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
How the wording drifted
Bohr’s saying was passed along in many forms. The imperative version on posters and quote sites is the most polished one, and the least sourced. The same line has also been credited to other people.
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Wording“Never express yourself more clearly than you are able to think” Paraphrase
Every source written by someone close to Bohr has “speak more clearly than I/one think(s).” The “express yourself … are able to think” form shows up in quotation books such as a 1997 scan of The Ultimate Book of Business Quotations (which spells his name “Niels Bohrs”) (Open Library ↗). A shorter version, “Never express yourself more clearly than you think,” appears in an entry of Jay Scott’s satirical Daily Whale dated 20 January 1992 (posted in his online archive) (the Daily Whale ↗).
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Wording“Never express yourself more clearly than you can think” Variant
A 1999 physics mailing-list post quotes this version and says it “has been attributed to Niels Bohr” (phys-l archive ↗).
✕
CreditJeremy Bernstein Also credited
Marvin Minsky’s The Society of Mind (1986) opens its postscript with “Never speak more clearly than you think. — Jeremy Bernstein,” and later books repeat that credit (Open Library ↗).
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CreditHoward H. Baker Jr. Also credited
Simpson’s Contemporary Quotations credits “Never speak more clearly than you think” to Baker on becoming President Reagan’s chief of staff, and David Crystal’s Words on Words also credits Baker (Open Library ↗).
✓The thought is Bohr’s. Abraham Pais, who worked with him, called it “Bohr’s precept never to speak more clearly than one thinks” in 1967 (Open Library ↗). The tidy “express yourself” wording is a later quotation-book version.
Context
Why Bohr said it
Bohr was famous for speaking slowly and haltingly, often with qualifications. His colleague Abraham Pais remembered him as “divinely bad as a public speaker.” Pais insisted this was not because of “his precept never to speak more clearly than one thinks,” since Bohr’s thinking was very clear (Open Library full-text search ↗).
The saying shows up in many first-person forms from people writing about Bohr. Lincoln Barnett (1964) has “I must never speak more clearly than I think.” Ruth Moore (1966) has “You see the problem is never to speak more clearly than I think.” Richard Rhodes (1986) has “I try not to speak more clearly than I think” (Open Library full-text search ↗). So many variants suggest a real habit of speech with no single fixed wording.
Bohr was divinely bad as a public speaker. This was not due to his precept never to speak more clearly than one thinks.
Where Rhodes got his version
In The Making of the Atomic Bomb (Simon & Schuster, 1986), Rhodes’s endnote credits “I try not to speak more clearly than I think” to J. Robert Oppenheimer’s 1963 lectures “Niels Bohr and His Times.” Rhodes’s bibliography lists those lectures as unpublished manuscripts in the Oppenheimer Papers. That makes it secondhand testimony, not something Bohr wrote.
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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 Bohr was a Danish physicist whose quantum model of the atom earned him the 1922 Nobel Prize in Physics. He led the Copenhagen institute that became a center of early quantum mechanics. Colleagues remembered him for his careful thinking and his halting, hard-to-follow way of speaking. He had a saying about not speaking more clearly than one thinks.
For writers & researchers
Cite this
Closest documented source
Abraham Pais, “Reminiscences from the Postwar Years,” in Niels Bohr: His Life and Work as Seen by His Friends and Colleagues, ed. Stefan Rozental (Amsterdam: North-Holland, 1967); reprinted in Niels Bohr: A Centenary Volume, ed. A. P. French and P. J. Kennedy (Cambridge, MA: Harvard University Press, 1985). The popular wording “Never express yourself more clearly than you are able to think” has no located primary source.
This verification page
Quotle.info. “Who really said ‘Never express yourself more clearly than you are able to think’?” Last verified 3 Nov 2026. https://quotle.info/who-said/never-express-yourself-more-clearly-than-you-are-able-to/