quote:
As I tried to explain in Message 223, strictly speaking, "absence of evidence" is never "evidence of absence." "Absence of evidence" is a neutral concept. You can get this by closing your eyes. We often use the term "absence of evidence" incorrectly when what we really mean is that a partial search was performed and nothing was found. This is, strictly speaking, more than just an "absence of evidence;" it is "evidence of absence" over the parameter space which was searched.
This is good.
I believe the original legal statement about absence of evidence means something like
'If there is no evidence E for X, X may still be true'
It's really a specialization of that statement where X is limited to cover the presence of something somewhere, but logically I believe it's the same kind of statement.
So in formula terms it could be expressed as
(E implies X) does not imply (not E implies not X).
This is logically correct and I think that's all the original legal principle is saying.
A complication arises when the evidence E is expected to exist if X is true. We now believe that X implies E, ie that in this case we need to reverse the implication direction.
In this case, we CAN use the absence of evidence E to disprove X as we can use the standard logical expression :-
(X implies E) implies (not E implies not X).
So for example, if a specific location is scanned by a cctv camera, and we are happy that a continuous record has been stored, then finding no evidence for the presence of an indvidual on the recording is evidence that they were not present.
Edited by Peepul, : No reason given.
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