We Don't Know What We Can't Know...

"Dead Evidence" is the information/evidence that we don't have.  It is often the missing information that had it been available during the original analysis of an event would reveal that the accepted conventional wisdom was wrong.

Dead Evidence is easier to understand when illustrated by an example.

Say a plane crashed and 10 people survived.  After interviewing the 10 survivors we discover that each of them performed a similar set of behaviors.  Since they all survived the crash, the similar behaviors is apparently enabled them to survive the crash.  Conventional-Wisdom thinking would encourage others to emulate these actions when they found themselves in the same situation.

Unfortunately, we don't know if the people who died in the crash did the same thing, i.e. the evidence died with them.  If they did, can we really say the shared behaviors contributed to their survival or would it be more correct to attribute it to something less tangible; perhaps luck?

More importantly, since we as a species have ultimately lived and/or died based our ability to see patterns of successful behavior and react accordingly, are we fooling ourselves into practicing patterns of behavior, superstitions, that have no bearing on the actual outcomes?

Only the dead evidence will let us know.

However, while we don't know what we can't know, we can know what we don't know.  It is the knowledge of what we don't know that enables us to use dead evidence.