“Absence of evidence is not evidence of absence.”

— Carl Sagan , book Cosmos

Martin Rees — Sagan refers to this quote in The Demon-Haunted World (1995) (see above)
Misattributed
Source: Cosmos

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Carl Sagan 365

American astrophysicist, cosmologist, author and science ed… 1934–1996

Tana French In the Woods

Misattributed
Source: In the Woods

“Absence of evidence is not evidence of absence.”

Martin J. Rees (1942) cosmologist, astrophysicist, Astronomer Royal, Master of Trinity College, President of the Royal Society

As quoted in Project Cyclops: A Design Study of a System for Detecting Extraterrestrial Intelligent Life (1971) http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730010095_1973010095.pdf by Bernard M. Oliver, and John Billingham, Ch. 2 : Life in the Universe, p. 3 ; this has frequently misattributed to Carl Sagan, who quoted it in some of his presentations.

“Doctors most commonly get mixed up between absence of evidence and evidence of abense”

Nassim Nicholas Taleb (1960) Lebanese-American essayist, scholar, statistician, former trader and risk analyst

“Even if the absence of evidence for a given god were not evidence of its absence, it would still be evidence that the belief in that god is unreasonable. That's the only proposition that any atheist of any kind has to demonstrate in order to win the argument. Because anything beyond that… is just having fun.”

Scott Clifton (1984) American television actor, musician, internet personality.

God, Atheism and Evidence, as Theoretical Bullshit, hosted on YouTube. (11 January 2010) http://www.youtube.com/watch?v=9stJ8h2ilZU

“Putting all this together, we see that religion is like Sagan’s invisible dragon. The missing evidence for any god is simply too glaring, and the special pleading too unconvincing, to make its existence anything more than a logical possibility. It’s reasonable to conclude, provisionally but confidently, that the absence of evidence for God is indeed evidence for his absence.”

Jerry Coyne book Faith vs. Fact: Why Science and Religion are Incompatible

Source: Faith vs. Fact (2015), p. 204

“Do you know what we call opinion in the absence of evidence? We call it prejudice.”

Michael Crichton book State of Fear

Source: State of Fear

“Appeal to ignorance — the claim that whatever has not been proved false must be true, and vice versa (e. g. There is no compelling evidence that UFOs are not visiting the Earth; therefore UFOs exist — and there is intelligent life elsewhere in the universe. Or: There may be seventy kazillion other worlds, but not one is known to have the moral advancement of the Earth, so we're still central to the Universe.) This impatience with ambiguity can be criticized in the phrase: absence of evidence is not evidence of absence.”

Carl Sagan (1934–1996) American astrophysicist, cosmologist, author and science educator

Referring to an aphorism of Martin Rees. (see Misattributed below)
Source: The Demon-Haunted World : Science as a Candle in the Dark (1995), Ch. 12 : The Fine Art of Baloney Detection, p. 221

“The absence of the improbable, the redundancy of the probable, is just as much conclusive evidence against conformity with scientific law as the too frequent occurrence of the improbable itself.”

Karl Pearson (1857–1936) English mathematician and biometrician

"The Scientific Aspect of Monte Carlo Roulette" (1894)

“In principle, it might be possible to obtain evidence of focal-attentive processing in the absence of awareness of what is being processed… in practice, however, a complete dissociation of consciousness from focal-attentive processing is difficult to achieve.”

Max Velmans (1942) British psychologist

Source: Is human information processing conscious?, 1991, p. 665; As cited in: Giorgio Marchetti, " Against the view that consciousness and attention are fully dissociable https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3279725/." Attention and consciousness in different senses (2011): 23.

“Reports that say that something hasn't happened are always interesting to me, because as we know, there are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns — the ones we don't know we don't know. And if one looks throughout the history of our country and other free countries, it is the latter category that tend to be the difficult ones.
The absence of evidence is not evidence of absence, or vice versa.”

Donald Rumsfeld (1932) U.S. Secretary of Defense

Department of Defense news briefing (12 February 2002)
Variant:
Now what is the message there? The message is that there are no "knowns." There are things we know that we know. There are known unknowns. That is to say there are things that we now know we don't know. But there are also unknown unknowns. There are things we do not know we don't know. So when we do the best we can and we pull all this information together, and we then say well that's basically what we see as the situation, that is really only the known knowns and the known unknowns. And each year, we discover a few more of those unknown unknowns.
:It sounds like a riddle. It isn't a riddle. It is a very serious, important matter.
:There's another way to phrase that and that is that the absence of evidence is not evidence of absence. It is basically saying the same thing in a different way. Simply because you do not have evidence that something exists does not mean that you have evidence that it doesn't exist. And yet almost always, when we make our threat assessments, when we look at the world, we end up basing it on the first two pieces of that puzzle, rather than all three.
:* Extending on his earlier comments in a press conference at NATO Headquarters, Brussels, Belgium (6 June 2002) http://www.nato.int/docu/speech/2002/s020606g.htm
2000s

“Absence of evidence is not evidence of absence.”

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