Several famous people have used this phrase in lots of situations. Recently, Neil deGrasse Tyson used it in the following way : “One of our mantras in science is that the absence of evidence is not the same as evidence of absence.” This outburst was in defense of a failure of his memory in quoting George W Bush. Tyson got it wrong and after some embarrassing back and forth, finally admitted his error.
In thinking about the meaning of the phrase I realized that the phrase can be nuanced to death. You could spin the phrase to mean pretty much anything.
So, how do you take the meaning?
- Evidence is evidence, and if there is no evidence to support a theory, there is no evidence. You cannot say that the absence of evidence proves the theory is false. You can only speak of things in the language of uncertainty, i.e., the theory is likely false if there is no empirical evidence to the contrary.
- If there is no elephant in the room, and if you don’t see any evidence there is an elephant in the room, this lack of evidence means there is no elephant in the room. So, a lack of evidence can be used as evidence of absence.
- That there is no physical evidence of mental telepathy means that mental telepathy does not exist.
- There is no evidence mental telepathy does not exist, therefore it exists. This is called an Argument from Ignorance.
Tyson said that the phrase was a scientific mantra. Why would he say that? Maybe his mantra is really, “Everything I say is correct and shame on you for questioning my veracity.”
Everything depends on evidence. In science evidence must be data indicating actual physical parameters. Evidence is measured, counted, photographed, etc.
Of course, there are the ever popular examples as follow:
- If a tree falls in the forest and there is no one to hear it, did it make a sound?
- If your wife talks to you during a football game, does this mean you are hard of hearing just because you didn’t hear her?
I am guilty of getting into some deep, unfamiliar waters here. This stuff probably comes under the heading of philosophy. I skillfully endeavored to not take philosophy in college. I was more interested in electrons and women, not necessarily in that order.
It is time to stop this article. I have a headache.