Niels Bohr? Hans Bohr? Werner Heisenberg? Oscar Wilde? Emilio Segrè? Carl Sagan? Anonymous?
The opposite of a deep truth is another deep truth.
Would you please help me to find a citation and the correct phrasing?
Quote Investigator: In 1949 the prominent physicist Niels Bohr published an essay titled “Discussion with Einstein on Epistemological Problems in Atomic Physics” which included a passage about “deep truths”. Boldface added to excerpts by QI:[ref] 1959 (1949 Copyright), Albert Einstein: Philosopher-Scientist, Edited by Paul Arthur Schilpp, Chapter 7: Discussion with Einstein On Epistemological Problems in Atomic Physics by Niels Bohr, Quote Page 240, Harper Torchbooks, Harper & Row, New York. (Verified with scans) [/ref]
In the Institute in Copenhagen, where through those years a number of young physicists from various countries came together for discussions, we used, when in trouble, often to comfort ourselves with jokes, among them the old saying of the two kinds of truth. To the one kind belong statements so simple and clear that the opposite assertion obviously could not be defended. The other kind, the so-called “deep truths,” are statements in which the opposite also contains deep truth.
Bohr labeled the remark a joke, and he used the phrase “old saying”. Thus, he disclaimed authorship; nevertheless, he usually receives credit for the statement.
Below are additional selected citations in chronological order. The phrasing of this notion varies; hence, this section begins with an overview:
1891: A Truth in art is that whose contradictory is also true
1949: ‘Deep truths’ are statements in which the opposite also contains deep truth
1967: Profound truths recognized by the fact that the opposite is also a profound truth
1971: The opposite of a profound truth may well be another profound truth
1980: The opposite of every great idea is another great idea
1980: The opposite of a shallow truth is untrue but the opposite of a deep truth is also true
1989: The opposite of a deep truth may again be a deep truth
In 1891 the renowned wit Oscar Wilde published an essay containing a thematically related statement:[ref] 1891, Intentions by Oscar Wilde, Essay: The Truth of Masks, Start Page 179, Quote Page 212, Heinemann and Balestier, Leipzig. (Google Books Full View) link [/ref]
For in art there is no such thing as a universal truth. A Truth in art is that whose contradictory is also true.
A separate article about Wilde’s expression is available here.
In 1949 Bohr published the essay containing the quotation. The passage was subsequently reprinted in other books and periodicals. For example, in 1962 “The New Yorker” magazine reprinted Bohr’s words in a section called “The Talk of the Town”.[ref] 1962 December 1, The New Yorker, The Talk of the Town: Notes and Comment, Start Page 51, Quote Page 52, Column 1, The New Yorker Magazine Inc., New York. (Online New Yorker archive of digital scans) [/ref] Thus, the remark achieved further circulation.
In 1967 the collection “Niels Bohr: His Life and Work as Seen by His Friends and Colleagues” appeared. Hans Bohr wrote a chapter about his father Niels Bohr, and he included a version of the saying:[ref] 1967, Niels Bohr: His Life and Work as Seen by His Friends and Colleagues, Edited by S. Rozental (Stefan Rozental), Chapter: My Father by Hans Bohr, Start Page 325, Quote Page 328, North-Holland Publishing Company, Amsterdam, Netherlands. (Verified with scans) [/ref]
One of the favorite maxims of my father was the distinction between the two sort of truths, profound truths recognized by the fact that the opposite is also a profound truth, in contrast to trivialities where opposites are obviously absurd.
In 1969 physicist Werner Heisenberg published “Der Teil und das Ganze”. An English translation appeared in 1971 under the title “Physics and Beyond: Encounters and Conversations”. Heisenberg described a discussion he had with a colleague which caused him to think of the adage he attributed to Bohr:[ref] 1971 Copyright, Physics and Beyond: Encounters and Conversations by Werner Heisenberg, Translator: Arnold J. Pomerans, German Title: Der Teil und das Ganze, Chapter 8: Atomic Physics and Pragmatism (1929), Quote Page 102, Harper & Row, New York. (Verified in hard copy) [/ref]
And so both our formulations contained a large grain of truth, and Paul and I could console ourselves with an oft-repeated dictum of Niels Bohr: “The opposite of a correct statement is a false statement. But the opposite of a profound truth may well be another profound truth.”
Also, in 1971 “The New York Times” reviewed Heisenberg’s book and reprinted the adage which enabled further propagation:[ref] 1971 January 17, New York Times, Section: The New York Times Book Review, (Book Review by Elting Morison of Werner Heisenberg’s “Physics and Beyond”) Start Page BR1, Quote Page BR31, New York. (ProQuest) [/ref]
In 1980 physicist Emilio Segrè published “From X-Rays to Quarks: Modern Physicists and Their Discoveries”, and he included an instance of the saying:[ref] 1980, From X-Rays to Quarks: Modern Physicists and Their Discoveries by Emilio Segrè (University of California, Berkeley), Chapter 14: Conclusions, Quote Page 292, W. H. Freeman and Company, San Francisco, California. (Verified with scans) [/ref]
… Bohr jokingly said that the opposite of a shallow truth is untrue but the opposite of a deep truth is also true …
Also, in 1980 astronomer Carl Sagan published “Cosmos”, and he included another version of the remark:[ref] 1980, Cosmos by Carl Sagan, Chapter: Appendix 1, Quote Page 347, Random House, New York. (Verified with scans) [/ref]
To take a modern example, consider the aphorism by the great twentieth-century physicist, Niels Bohr: “The opposite of every great idea is another great idea.”
In 1989 the book “From A Life Of Physics” included a chapter reprinting a lecture from Werner Heisenberg which included the following:[ref] 1989, From A Life Of Physics by Hans A. Bethe, P.A.M. Dirac, W. Heisenberg et al, Chapter: Theory, Criticism and a Philosophy by Werner Heisenberg, Start Page 31, Quote Page 55, World Scientific Publishing Company, Singapore. (Google Books Preview) [/ref]
Then I remembered that Niels Bohr used to say, “If you have a correct statement, then the opposite of a correct statement is of course an incorrect statement, a wrong statement. But when you have a deep truth, then the opposite of a deep truth may again be a deep truth.”
In conclusion, Niels Bohr popularized this expression. He employed a version in an essay published in English in 1949, but he called the remark an “old saying”. Thus, it was circulating previously, and Bohr was not the originator. Different phrasings have proliferated over time.
(Great thanks to Daniel Sandberg and Mark Wainwright whose inquiries led QI to formulate this question and perform this exploration. Wainwright helpfully pointed to the statement by Hans Bohr. Further thanks to previous researchers Fred R. Shapiro and Ralph Keyes who identified key citations.)
Image Notes: Public domain illustration from geralt at Pixabay of arrows pointing in opposite directions. Image has been resized.