Yes, In Many Cases The Absence of Evidence IS Evidence Of Absence
The argument that some nut-job theory should be believed because “The absence of evidence is not evidence of absence” is totally stupid
I can no longer quietly sit by and let people say a blatantly stupid thing like “The absence of evidence is not evidence of absence” while a bunch of other intellectually-challenged fools nods their heads in dumb agreement.
The fact is that the absence of evidence always lies someplace between being totally worthless proof that the claim is false and being totally convincing proof that the claim is false depending on how likely it is that there would be evidence available if the claim were true.
We ask, “If the claim is true are there valid reasons why there might not be evidence available to support it?”
If not, then the absence of evidence is indeed strong evidence that the claim is false
There Are No Witnesses To Confirm The Defendant’s Alibi
Suppose a defendant claimed that he could not be the killer because he was at a particular bar at the time of the murder, but no one can be found who saw him at that bar. Is the absence of evidence that the defendant was at the bar evidence that he wasn’t there?
To determine the defendant’s guilt the jury considers these underlying questions:
- Was the bar crowded or almost empty?
- Was the bartender alert or half asleep?
- Did the people at the bar have a reason to lie about not seeing the defendant?
- Did the defendant huddle in the corner or get into a noisy argument?
- Was the bar quiet or was everyone watching a game on the TV?
- Were there surveillance cameras operating that would have recorded the defendant if he were there?”
Based on how the jury answers these questions the jury might conclude that the absence of evidence that the defendant was at the bar at the time of the murder is actually evidence that the defendant was lying about being there.
The Claim That Aliens Wander The Streets Of London
Suppose someone claimed that beings with two heads and four tentacles instead of arms roam the city of London?
The underlying facts are:
- 1) Almost 700,000 CCTV cameras surveil the city of London twenty-four hours a day.
- 2) These camera feeds are constantly monitored and the recordings are saved for some material period of time.
- 3) London is a heavily populated city.
- 4) An overwhelming percentage of London’s population carries a cell phone that has a camera
If these beings existed it is extremely likely that they would have been photographed.
The absence of photographic evidence that beings with two heads and four tentacles instead of arms roam the city of London is extremely strong evidence that the claim is false.
The Claim That Sasquatch Wanders The Forests Of Oregon
Compare that with the claim that Sasquatch lives in the forests of Oregon.
What are the reasons why there might not be evidence if the claim were true?
- 1) Portions of Oregon are heavily wooded and unpopulated
- 2) Sasquatch are reputed to be timid, solitary creatures who actively avoid human beings
- 3) There are no comprehensive surveillance networks covering these wilderness areas
- 4) There has not been a massive, coordinated effort that could be expected to so thoroughly search several thousand acres that it would be likely to obtain photos of sasquatch if he/she actually existed
For these reasons, the absence of evidence of sasquatch’s existence is only slight evidence that the claim is false.
How We Decide If The Absence Of Evidence Is Evidence Of Absence
We decide if the absence of evidence is, in fact, evidence of absence by asking, “If the claim were true is it likely that evidence of its truth would exist?”
If it is likely that such evidence would exist if the claim were true then the absence of such evidence is, in fact, material evidence of that the claim is false.
If it is not likely that such evidence would exist if the claim were true then the absence of such evidence is not material evidence of that the claim is false.
People Who Babble This Nonsense Argument
So, the next time some random person posts a tweet arguing that, even though he has no evidence to support his latest nut-job conspiracy theory, that’s no reason to say it isn’t true because “The absence of evidence is not evidence of absence,” just mentally picture him waving a big red flag with the word “Moron” written on it.