The Absence of Evidence
Quite a few times, recently, I have heard Christians cite the time-worn words “absence of evidence is not evidence of absence”. It’s a catchy sound bite and a highly successful meme, but it is utterly false. Absence of evidence most certainly is evidence of absence.
Before I explain why, I think it’s important to understand the difference between evidence and proof. The two are often used synonymously, to the point where the semantic lines have blurred. Strictly speaking though, evidence is defined as:
Facts or observations presented in support of an assertion.
Proof has a number of definitions, but I think this one is the most appropriate for the point I am trying to illustrate:
That degree of evidence which convinces the mind of any truth or fact, and produces belief; a test by facts or arguments that induce, or tend to induce, certainty of the judgment; conclusive evidence; demonstration.
To summarise this as simply as possible, evidence doesn’t have to be conclusive, it is gradual. In rational terms, the greater the amount and the stronger the nature of the evidence, the more secure becomes the claim it supports. As more evidence becomes available though, the balance can shift either for or against the claim at any one time. One could see it as a sort of ongoing tug of war, where the more ground you take from your opponent, the harder they have to work to recover the position before they can look to take the advantage. Proof, on the other hand, is seen as holding a sense of finality – leaving the truth of the claim beyond any reasonable doubt.
There is a saying (the original source of which I am unable to ascertain) that “proof is for mathematicians and alcoholics”, which is very apt when applied in response to the “absence of evidence” saying. Because, even though they say ‘evidence’, what the people who use the quote really mean is ‘proof’. What they’re saying is: just because there is no evidence that God exists, doesn’t prove that he doesn’t exist. And, of course, they’re right – it doesn’t. It doesn’t show that God does not exist, beyond any reasonable doubt, but it most certainly is evidence against the existence of God.
Let’s say that you are in a large, empty, rectangular room, on your own, or at least as far as you can tell. The claim we will consider as a thought experiment is: there is a twelve piece marching brass band in the room with you. How will you analyse the truth of the claim? Can you see a marching band? Can you hear a marching band? The answer is no, so you are lacking visual or audio evidence of the presence of a marching band. Is there any other evidence that a marching band may be in the room with you? None. There is no evidence whatsoever to support the claim that there is a marching band in the room with you. Is this fact, this absence of evidence, itself evidence that there is no marching band in the room with you? Of course it is! When analysing any claim, the absence of evidence for its truth can automatically be counted as evidence in favour of its falsity. Not conclusive proof, but strong, valid evidence.
The “absence of evidence” quote is normally one of the last resorts before the proposal to agree to disagree. To my mind, it is to all intents and purposes a concession of, and withdrawal from the argument. It translates roughly as: I have no evidence to support my claims, but that doesn’t mean that they’re false. What else could it mean? If someone accuses you of having no evidence for a claim, but you believe that you do have evidence, you don’t start defending your claim as if you didn’t have evidence, you present it. If someone uses that phrase, then it implies agreement that there is no evidence. How can they proceed in a rational discussion if they have just admitted that they have no evidence? What can you say in response? Not an awful lot, in my opinion. If you have stressed the importance of the burden of proof (or should that be burden of evidence?) and that it lies with the positive claimant, and reiterated the points I have tried to make in this article, then I believe that the discussion should end there. You can only hope that the person with whom you have been talking will give some serious thought to the implications of acknowledging the absence of evidence.
A Load of Bright 
I’m not sure that I completely agree on “Absence of evidence most certainly is evidence of absence,” at least so far as scientific reasoning goes. You simply can’t make an empirical observation on what is not there to observe. That said, you can make the reasonable conclusion that the inability to find *insert phenomenon here* actually does mean it’s not there. That’s an assumption however, not evidence, strictly speaking.
But that’s just semantics – I agree, the “absence of evidence” argument is a desperate plea to defend vacuity and empty rhetoric.
Dan - September 20, 2007 at 6:24 pm |
Hi Dan,
Thanks for your comment. I see where you’re coming from, but I still think the absence of evidence can be classed as evidence. It seems to me that you may be defining evidence a bit too strictly. Bear in mind again the definition of evidence, “facts or observations that can be presented in support of an assertion”. The fact that there is no known evidence to support the truth of a claim is an observation that supports the view that the claim is false, which classes it as evidence within the definition I’m using (which I think is normal and would be widely accepted). Evidence doesn’t have to be something physical like a fossil.
tobe38 - September 20, 2007 at 6:31 pm |
The absence of evidence is just that: no evidence. It is not necessarily evidence of absence; no logical atheist claims that it is.
There’s the old story of the black swan: civilized people in the Old World had never observed a swan that was anything other than white. The preponderance of evidence led to the theory that all swans were white. As the Old World moved in on the New, however, black swans were discovered in Australia. New evidence. New theory.
But in the face of zero evidence, there’s no reason to believe in a god. The problem with religionists is, of course, their stubborn refusal to acknowledge that they have absolutely no evidence. In fact, there’s plenty of evidence to the contrary. If, however, the godpushers do find their black swan, we atheists will have to reevaluate our theories. Of course, accepting a god for which there is evidence is no longer a question of blind faith; it’s science.
But I’m not holding my breath. Theocrats have been looking actively for their magic swan since the beginning of time, and they’ve yet to find it.
The Exterminator - September 20, 2007 at 7:26 pm |
I would add a condition to this though: absence of evidence is evidence of absence, IF the state of affairs of the claim being true is clearly different from the state of affairs in the claim was false.
For instance:
“There is no evidence that Tobe was not in New York at the time of the crime”
…in no way proves that you were in New York, assuming you have no alibi at all.
So the lack of evidence that you were NOT in New York is not evidence that you were. Unless of course there is evidence we would expect to find if you weren’t there, that is lacking. And that is the difference.
That there is no evidence of god does not in itself ‘automatically’ prove that he doesn’t exist on its own. But when you add the criterion that his existence would result in evidence we would expect to find and that evidence is not present, then it becomes evidence against him.
This is why the marching band in the small room is an excellent analogy, but it too reinforces the presumption that we would expect to have evidence of the band’s existence. (Which of course we would.)
If the state of affairs of a claim’s veracity are indistinguishable from the claim’s falsity, and we would not expect anything differentiating between them, then there is no proof either way. In this situation however, the claim is meaningless. e.g.: “there is a teapot orbiting Pluto.” This doesn’t make the likelihood 50/50 of course; the burden of proof is still on the claimant.
evanescent - September 20, 2007 at 7:29 pm |
Wait….there’s a teapot orbiting Pluto now? I thought it was orbiting the moon!
Darren - September 20, 2007 at 7:58 pm |
It was moved there by the Flying Spaghetti Monster!
evanescent - September 20, 2007 at 8:08 pm |
@ The Exterminator
That’s exactly what I am claiming. And I’m an atheist and, I hope, logical. The absence of evidence in favour of the claim (that God exists) is itself evidence against that same claim. It is not conclusive proof, but it is evidence. It doesn’t even have to be good, convincing evidence, but it isevidence.
tobe38 - September 20, 2007 at 8:42 pm |
Ah… so you’re using the colloquial use of the word “evidence,” and not the scientifc/empirical use of the word. Then yes, absolutely.
Dan - September 20, 2007 at 8:51 pm |
You people are too damn logical, what with all your mental gymnastics and brain tricks. God’s sitting here in a chair across from me, and I’m having a nice conversation with him. In fact, he likes cigars.
We’re heading down to the bank in a few minutes, to withdraw some of my money. He has this wonderful investment opportunity for me, and I’m not letting you unbeleivers in on it. (He told me not to.)
Absence of evidence, indeed. {snort}
Spanish Inquisitor - September 20, 2007 at 9:49 pm |
Well, tobe:
This is not one on which we can agree to disagree. You are dead wrong, unless you’re using the loosest definition of the word “evidence.” No evidence is just no evidence.
To conclude that something does not exist also requires positive evidence pointing to its nonexistence. You could make the argument — with which I would wholeheartedly agree — that there is a great amount of evidence pointing to the conclusion that god does not exist. But the fact that there’s no evidence pointing to god’s existence is insufficient, by itself, to come to any conclusion. Remember those black swans.
Now, obviously, in real life, you and I and every other member of the Atheosphere keep asking those zealous religionists where their evidence is for a god. But their inability to provide evidence only shows that they’re liars or fools or both. No one has come up with evidence to show that there’s life on other planets. But I would never say — and I expect you would never say it, either — “Oh, there’s no evidence that there’s life anywhere else in the universe, which is evidence that there’s no life anywhere else in the universe.”
This is all semantics, though. It should be clear to any rational human being that there’s no evidence supporting the existence of any gods. I think that statement should be sufficient to explain one’s atheism.
The Exterminator - September 20, 2007 at 11:23 pm |
If there’s a personal god, you’d expect him to “make some noise.” The absence of any personal-god activity in spite of claims that he acts in response to various circumstances, is strong evidence that he is a fabrication of the ones making the claims. It all depends on how you define the thing you’re trying to disprove.
Polly - September 20, 2007 at 11:45 pm |
@ The Exterminator
No offence, but I don’t think you’ve read the article or my previous comments thoroughly.
I gave a definition of “evidence” in the article and linked to a source for it: Facts or observations presented in support of an assertion. It doesn’t say it has to be sufficient for any conclusions to be drawn. I think this is a good definition of evidence, and the context in which you are using it is really where the word “proof” should be used, which I also sourced. This may well come down to a matter of word definitions, but I think I’m using the correct ones.
It may be no evidence with respect to one claim, but could itself become evidence to support a counter-claim. Remember, evidence doesn’t have to be empirical (go back to the definition I gave). And it doesn’t have to be sufficient for a conclusion, it just has to support an assertion, no matter how weakly. Conclusions are drawn on weight of evidence, when lots of it has been gathered from various sources. It is often the case that one piece of evidence alone is insufficient to reach a firm conclusion, but that all the evidence combined is plenty. The absence of evidence for the existence of god is one piece of evidence that he doesn’t exist. Not conclusive proof, just one piece of evidence.
To conclude beyond doubt, yes. But that again does not apply to evidence, it would to proof.
I may well do a follow up article on this. Strictly speaking, there is evidence for God. It just happens to be incredibly weak, flawed, and so effortlessly refuted that it can be dismissed almost immediately. When we say there is no evidence for God, what we really mean is that there is no good evidence for God, and what little evidence there is, is so poor that in every-day terms there may as well be no evidence for God.
tobe38 - September 21, 2007 at 5:25 am |
tobe,
To your 8:42pm – since you have set this standard, I can meet it. “The absence of evidence in favour of the claim (that God exists) is itself evidence against that same claim. It is not conclusive proof, but it is evidence. It doesn’t even have to be good, convincing evidence, but it isevidence.”
I have eye witness evidence that god is real. I was there when he manifest his reality to me. I can deliver for you 1,300 other people who happen to go to my church who have witnessed the same thing.
Just as the only evidence of your birth is the eye witness accounts.
I know I am being shallow, but you did set the bar pretty low for evidence.
Geno - September 21, 2007 at 4:43 pm |
tobe:
Well, unfortunately, Geno’s right. You’ve set the bar incredibly low for evidence. If evidence is facts or observations — not necessarily empirical ones (which seems to be your spin) — in support of an assertion, then you could supply evidence for the existence of the tooth fairy. (There was a coin under my pillow, after all.) Look, you can’t base a serious philosophical ramble on a definition from Wiktionary!
Most of us in the atheist community — in fact most reasonable people — use the word “evidence” in a more specific sense. You can hunt for different literal denotations, but you’re just playing dictionary games. There’s no viable evidence for god. If every idiot’s insistence that he had a dream-within-a-dream is “evidence” in your book, then why use the word “evidence” at all?
And, given that your definition of evidence is so loosy-goosy, what’s your point in this post?
The Exterminator - September 21, 2007 at 5:34 pm |
Exterminator,
I picked this off of your blog – “Can a “liberal” political leader who professes faith — even one who picks and chooses practices from various different religions — be truly tolerant? Or is there something inherent in every system of supernatural belief that causes its adherents to be enemies of those with differing worldviews?”
How do you yourself differ from this description? You have set yourself up as the enemy of those with a differing worldview? This can be seen by your phaseology above – “If every idiot’s insistence that he had a dream-within-a-dream is “evidence…” Wouldn’t you have to say that your atheism (and that of all adherents ) are by nature enemies of others?
But I do agree, it is a battle of worldviews!
Geno - September 21, 2007 at 5:59 pm |
Geno:
Your question to me is off-topic here. If you’re going to comment on my blog, do it there. Don’t take up tobe’s space. Feel free to repost your comment in the appropriate place, and I’ll respond.
The Exterminator - September 21, 2007 at 6:34 pm |
Exterminator,
I will
Geno - September 21, 2007 at 6:35 pm |
Notwithstanding my previous comment, as a lawyer I always think of evidence as I learned it in law school, and as I practice it in court. Before evidence can even be considered, it must be admissible in court. The Rules of Evidence dictate what can be admitted and what can’t. It’s not an easy threshold to pass. In the generic sense of evidence, everything is evidence. My long dead grandmother’s recollection of events her great grandmother told her would be evidence, but not admissible in a court of law.
By any standard, conclusive proof of a god’s existence would never be found in a courtroom. I wrote a post that touched on this a few months back.
Spanish Inquisitor - September 21, 2007 at 9:06 pm |
@ Geno,
Yes, you provided evidence, just extremely weak, easily refuted evidence.
@ The Exterminator
It’s not just me setting the bar low, I think my definitions are correct.
Yes, you’re right and I don’t have a problem with that. As far as a child is concerned, they do have evidence of the tooth fairy. And they’re right, they do have evidence, it’s just weak evidence that they will find out in later life is actually very easily refuted.
Evidence is judged on quality, as I said. Take a court case and a murder. Both the prosecution and the defence will present their evidence. The prosecution has DNA samples that show the defendant was at the scene of the crime. The defence has a witness that will testifiy that the defendant was with them at the time of the crime, 200 miles away. Both have provided evidence, even what appears to be strong evidence, but one of them is wrong. One side has presented evidence that is flawed.
I don’t think this is just me ranting subjectively. We can judge the quality of evidence by how well it stands up to scrutiny.
Can you provide a better definition?
No, what they actually do is dismiss evidence that is so weak that it falls at the first fence. Some evidence is so weak that it doesn’t even get far enough to be deemed evidence. Richard Dawkins pointed out that technically speaking, we can never be absolutely 100% certain of anything, but that words like “know” and “certain” have to mean something – we have to draw a line somewhere. I think this is the case with evidence too.
Because you can add words to qualify it – like you just did with the word “viable”.
I thought my point was clear: the absence of evidence for the existence of God isevidence for the absence of God. I’m not necessarily saying it’s strong evidence (and it certainly isn’t conclusive proof), but I don’t think it’s especially weak either.
In my article I used the example of a marching band in the room with you. Do you really not think that the absence of any visual, audio or any other kind of evidence to suggest a marching band is present with you can be counted as evidence that no such marching band is there with you?
tobe38 - September 22, 2007 at 12:30 am |
@ Spanish
I think this ties in nicely with what I’m saying. For something to be evidence per se is actually quite easy, but the fact is that we all demand a certain standard of evidence, even if some people’s standards are higher than others. So on a day to day basis we don’t just refer to anything as evidence. The question of what is admissable in court is a good example.
tobe38 - September 22, 2007 at 12:33 am |
One crucial point which no-one seems to have brought up yet (forgive me if I missed it) is the question of whether we would expect to see evidence. If we are speaking of something where we would expect to see evidence if it existed, then absence of evidence is indeed evidence of absence. On the other hand, if we are speaking of something where the evidence may be out there, but we haven’t done a thorough search yet, and there’s no obvious reason why we would have the evidence already, then absence of evidence is most certainly not evidence of absence. A personal God falls into the first category: we would expect to see evidence. Alien life forms, on the other hand, may well fall into the second category.
Lynet - September 22, 2007 at 6:41 am |
Hi Lynet
I made the point about expectation in the 4th comment down.
evanescent - September 22, 2007 at 9:25 am |
@ Evanescent and Lynet
The expectation of evidence is a very important point, which I neglected to mention. Thanks for point it out 🙂
tobe38 - September 22, 2007 at 10:28 am |
Lynet,
“If we are speaking of something where we would expect to see evidence if it existed,”
I touched on this by stating that we’d expect something from a “personal” god who believers describe as active in the natural world as opposed to a generic, unknowable deity. Studies indicating that prayer for patients is useless lend strong support to denying the existence of a personal god.
Polly - September 26, 2007 at 7:06 pm |
[…] tobe38 : The Absence of Evidence […]
Challenge Religion - Today’s Top Blog Posts on Atheism - Powered by SocialRank - October 1, 2007 at 10:00 am |
I too have had people claim that absence of evidence is not evidence of absence….in my eyes…it sort of looks that way though.
I simply remind the person making the wise-arse remark about The burden of proof. 70% don’t know what it means and it shuts them up, the 30% that do know what it means soo shut up.
Easy win. Loving the blog by the way, first stop here, and I can’t stop reading! Thank you!
dontcrossthebeams - November 11, 2007 at 12:39 am |
@ dontcrossthebeams
Thanks for your comment.
Sometimes it is, and other commenters have pointed out that often it’s a question of whether or not we should expect to find evidence – a point i overlooked.
A very wise course of action. It’s really not a point we should dignify by getting bogged down with. As you say, the burden of proof is clear.
On the contrary, thank you! I’m going through a bit of a dry patch writing at the moment, but it’s good to know new readers are still finding their way here. 🙂
tobe38 - November 11, 2007 at 12:44 am |