Sagan really did write these eight words — in the Introduction to The Dragons of Eden (Random House, 1977), page 7, arguing that neuroscience’s failure so far to localize every higher brain function proves nothing about what future work will find. What he did not do is coin the line. Quote Investigator finds the identical maxim in print in December 1895 ↗, and NASA’s Project Cyclops report had already run it as a chapter epigraph over the name of the cosmologist Martin Rees.
“Absence of evidence is not evidence of absence” Carl Sagan, The Dragons of Eden (New York: Random House, 1977), Introduction, p. 7. Sagan wrote the line but did not coin it: Quote Investigator documents an exact match in December 1895, credited to Dugald Bell, and NASA's 1971 Project Cyclops report used it as a chapter epigraph credited to Martin Rees. Verified at quotle.info
Image direction — grounded in this quote’s real context; paste into your image tool
In context
Evoking the world of Carl Sagan — American astronomer, planetary scientist & science communicator, Cornell University. Theme: "Absence of evidence is not evidence of absence". 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.
Minimalist
Minimalist editorial slide for the quote "Absence of evidence is not evidence of absence". 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
The source
Work
The Dragons of Eden: Speculations on the Evolution of Human Intelligence
Location
Introduction, page 7
Publisher & date
Random House, New York — 1977 (Pulitzer Prize for General Nonfiction, 1978)
Phrase first recorded
December 1895, credited to Dugald Bell in The Glacialists’ Magazine (per Quote Investigator) — not by Sagan
… because they have been unable to isolate and localize all higher brain functions, no future generation of neuroanatomists will be able to achieve this objective. But absence of evidence is not evidence of absence.
Introduction, p. 7
The first clause is a conclusion Sagan rejects; the maxim is his rebuttal to it, not his claim.
3 January 1887 — six of the eight words, at a London learned society. The Reverend William Wright, arguing that thin Egyptian records did not disprove Hittite settlement in southern Palestine, told the Victoria Institute that “the absence of evidence is not evidence.” The paper was printed in the society’s Journal of the Transactions, volume 21, in 1888 — Quote Investigator’s earliest match ↗.
December 1895 — the exact eight words, in a glacial-geology journal. Writing on Scandinavian boulders in The Glacialists’ Magazine, Thomas Sheppard set the maxim in quotation marks and handed the credit to somebody else, remarking that it had been said by Mr. Dugald Bell. QI calls this the exact match ↗ and notes that earlier instances may still be found.
Project Cyclops — the maxim reaches NASA, over Martin Rees’s name. Chapter 2 of the Project Cyclops design study, written up from the Stanford/NASA Ames 1971 summer faculty program and catalogued as NASA CR-114445, opens with the line credited to Rees, and the chapter then argues from it: “evidence in the sense Rees uses the word in the quotation above” (p. 3) ↗.
1977 — Sagan puts it on page 7, and it becomes his. In the Introduction to The Dragons of Eden he uses it against readers who treat a gap in the brain map as proof the territory is empty. Wikiquote sources the sentence to that page ↗ — and then lists the same eight words again under Misattributed, where the aphorism is credited to Rees.
The passage quoted here is from The Dragons of Eden, published by Random House in 1977 ↗, so Sagan’s text remains in copyright in the United States and is excerpted here for identification and comment. The eight-word maxim itself is far older — it was in print by December 1895 — and that Victorian wording is long out of copyright; what is protected is the surrounding prose.
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
Genuine wording, borrowed maxim
This is not a fake quote. Sagan wrote it, and it is sourced to a page number in one of his books. What goes wrong is the credit line: the eight words are shared as Sagan’s coinage, and they are not his — they were a working scientists’ maxim in print before he was born.
✕
CoinageCarl Sagan Wrote it, didn’t coin it
Sagan is routinely presented as the source of the phrase. Quote Investigator ↗ traces six of the eight words to a paper the Reverend William Wright read to the Victoria Institute in London on 3 January 1887 (“the absence of evidence is not evidence”), printed in the society’s Journal of the Transactions in 1888 — and finds the exact eight words in The Glacialists’ Magazine for December 1895. QI’s verdict is that the maxim evolved over time and that Sagan helped popularize it long after it was in circulation.
✓The honest credit is a chain rather than a name: a Victorian scientists’ maxim, credited in December 1895 to Mr. Dugald Bell, carried into the space age as a Martin Rees epigraph in NASA’s Project Cyclops report, and made famous by Carl Sagan, who wrote it on page 7 of The Dragons of Eden in 1977. Quote Investigator’s chronology ↗ is the best account of the route, and it warns that earlier instances may still surface.
Context
What silence proves
The line is a rule about what silence is allowed to prove. Sagan reaches for it in the Introduction to The Dragons of Eden against one specific bad inference: because no one had yet isolated and localized every higher brain function, some readers had concluded that no one ever would — and, by extension, that mind must be something other than anatomy. His answer is that a gap in the map is not a hole in the territory.
That is also why the maxim first reached a wide scientific audience through the search for extraterrestrial intelligence. NASA’s Project Cyclops study opened its chapter on life in the universe with the line, credited to Martin Rees, because the report had to justify an expensive search that had so far found nothing at all. The phrase licenses a search without promising a result — which is exactly why Quote Investigator’s chronology ↗ finds it in glacial geology in 1895, in a naturalist’s hunt for orchids in 1947, and in speculation about surviving moa in New Zealand in 1953.
“It has been remarked by Mr. Dugald Bell that ‘absence of evidence is not evidence of absence.’” — Thomas Sheppard, The Glacialists’ Magazine, December 1895
The people who used it before Sagan
Between 1887 and 1977 the maxim circulates in precisely the fields where absence is the daily working problem — archaeology, glaciology, natural history, palaeontology. QI records ↗ a bull-pedigree dispute in London’s Live Stock Journal on 16 October 1891 that turns on “the distinction between absence of evidence and evidence of absence”; the Dublin geologist W. J. Sollas attacking the fallacy in the Quarterly Journal of the Geological Society in August 1895; and The Yorkshire Post applying it to vanished boat burials on 14 August 1939.
The modern chain runs through astronomy. After the Project Cyclops epigraph, the astronomer Richard Berendzen used the maxim at a symposium on life beyond Earth reported in December 1972, and Sagan put it into print in 1977. Sagan used it once more, in The Demon-Haunted World (1995): Wikiquote places it in chapter 12, “The Fine Art of Baloney Detection” ↗, where he offers it as the cure for the appeal to ignorance.
Explore
Filed under
More provenance-checked quotes on the same theme, each with its reuse status.
1934–1996 · American astronomer, planetary scientist & science communicator, Cornell University
Carl Sagan was a Cornell planetary scientist who became the best-known science communicator of his generation through Cosmos, and who spent his last years writing about how to tell sound reasoning from bad. The Dragons of Eden, the 1977 book this line comes from, is his speculative account of how human intelligence evolved; it won the Pulitzer Prize for General Nonfiction in 1978. He was also a habitual quoter of other people — Wikiquote’s Sagan page ↗ lists several lines he passed on rather than invented, and files this one among them.
For writers & researchers
Cite this
The Dragons of Eden (1977), Introduction, p. 7
Sagan, Carl. The Dragons of Eden: Speculations on the Evolution of Human Intelligence. New York: Random House, 1977, Introduction, p. 7. Earliest exact match documented by Quote Investigator: Thomas Sheppard, “On the Occurrence of Scandinavian Boulders in England,” The Glacialists’ Magazine 3, pt. 3 (December 1895): 132, crediting Dugald Bell.
This verification page
Quotle.info. “Who really said ‘Absence of evidence is not evidence of absence’?” Last verified 10 Aug 2026. https://quotle.info/who-said/absence-of-evidence-is-not-evidence-of-absence/