absence of evidence, evidence of absence

[Feil]

"Absence of evidence is not evidence of absence."

How the hell did this get to be a truism? The very nature of proof by negation is the absence of evidence--

Suppose there is a dog on my desk.
1: if there was a dog on my desk, I would be able to see it
2: I cannot see a dog on my desk
3: Therefore there is no dog on my desk.

--2 is absence of evidence, and 3 is a conclusion of absence based on 1.

This doesn't even begin to take Occam's Razor into the equation, which tells us that given two conclusions, one of which relies on the existence of something not known to exist and one of which does not, the one which does not is preferred.

How do people get off claiming such ridiculous things? How do they live their lives according to such principles. And how, in the name of all that is good and holy, did something so obviously false become 'obviously true'?

[Ritterin Sophia]

Listen, if someone's using that argument you're in Retarded Fundie land and any attempt at rational logical discourse on your part is doomed to failure from sheer stupidity.

[Darth Wong]

"Absence of evidence is not evidence of absence."

How the hell did this get to be a truism?

It's cleverly worded, therefore it must be true. It's kind of like the Rhyming Rule, where any slogan that rhymes is twice as credible as one that doesn't.

The very nature of proof by negation is the absence of evidence--

Suppose there is a dog on my desk.
1: if there was a dog on my desk, I would be able to see it
2: I cannot see a dog on my desk
3: Therefore there is no dog on my desk.

--2 is absence of evidence, and 3 is a conclusion of absence based on 1.

This doesn't even begin to take Occam's Razor into the equation, which tells us that given two conclusions, one of which relies on the existence of something not known to exist and one of which does not, the one which does not is preferred.

The statement would actually be technically correct if it was slightly reworded, and used in a specific sort of case. For example, you would have to reword it from "absence of evidence is not evidence of absence" to "absence of evidence is not absolute proof of absence", and even then, it would only be true for statements which are sufficiently vague as to be untestable. Therefore, the more correct form of this statement would be "Absence of evidence of a vague, untestable phenomenon is evidence for, but not absolute proof of, the non-existence of that phenomenon". But that suffers from the grievous flaw of being correct, whereas the earlier statement sound neat, thus making it vastly superior despite being false.

How do people get off claiming such ridiculous things? How do they live their lives according to such principles. And how, in the name of all that is good and holy, did something so obviously false become 'obviously true'?

It became "obviously true" because people desperately want to believe in things for which not a shred of objective evidence exists.

[Rye]

"Absence of evidence is not evidence of absence."

How the hell did this get to be a truism? The very nature of proof by negation is the absence of evidence--

Suppose there is a dog on my desk.
1: if there was a dog on my desk, I would be able to see it
2: I cannot see a dog on my desk
3: Therefore there is no dog on my desk.

--2 is absence of evidence, and 3 is a conclusion of absence based on 1.

This doesn't even begin to take Occam's Razor into the equation, which tells us that given two conclusions, one of which relies on the existence of something not known to exist and one of which does not, the one which does not is preferred.

How do people get off claiming such ridiculous things? How do they live their lives according to such principles. And how, in the name of all that is good and holy, did something so obviously false become 'obviously true'?

In addition to what Mike said, a lot of things may be true, just not strictly evidencable. It would be one annoying, pedantic fuck that went out of his way to demand evidence that I took my dogs for a walk last wednesday when nobody else was home. Of course, there's no evidence I really did do it or not, other than my say-so. It's also an untestable claim that is entirely believable given that I can prove I have dogs, and walking dogs is a routine thing in our society. Its triviality lends it more credibility than totally unevidenced or anecdotal entities that are largely unbelievable if you change their names.

"Evidence of absence is not absence of evidence" may be true if we're talking about metaphysical, unknowable definitive truth as distinct from what is empirically/rationally discernable to be true within some degrees of likelihood and accuracy. This is to do with how we get knowledge or epistemology, and there we can conclude that god is as knowable, and therefore as rational to propose the existence of, as entities we can imagine in a matter of seconds, be they my mystical arse, intangible rapist rugby teams or deicidal dragons.

My proposed version: "Absence of evidence is not evidence of absence perhaps, unless we expect to see evidence, but stfu, theism is still nonsensical, it still has to rationalise how stuff you're meant to believe in appear to be imaginary. "Oh wow, my god doesn't appear to exist, but he does, honestly!!!" Riiiight. So what're you gonna do now, huh, bitch? Bitch? Bitch please."

[Metatwaddle]

"Absence of evidence is not evidence of absence."

How the hell did this get to be a truism? The very nature of proof by negation is the absence of evidence--

Suppose there is a dog on my desk.
1: if there was a dog on my desk, I would be able to see it
2: I cannot see a dog on my desk
3: Therefore there is no dog on my desk.

--2 is absence of evidence, and 3 is a conclusion of absence based on 1.

This doesn't even begin to take Occam's Razor into the equation, which tells us that given two conclusions, one of which relies on the existence of something not known to exist and one of which does not, the one which does not is preferred.

How do people get off claiming such ridiculous things? How do they live their lives according to such principles. And how, in the name of all that is good and holy, did something so obviously false become 'obviously true'?

For what it's worth, I can think of an instance or two where it would apply. The main one that comes to mind is the existence of other intelligent life in the universe. We haven't found any yet, but that does not at all mean it's not there. I don't know much about what the chances are, but with all the possible planets out there, it does seem reasonable that there is some other species with something resembling a "civilization" in the universe.

I actually found the quote "Absence of evidence is not evidence of absence" attributed to the inimitable Carl Sagan. I suspect the life-in-outer-space thing was the context for the quote. Dr. Sagan, I suspect, would be rather annoyed to know that religious apologists were co-opting his line into a truism that doesn't always hold true.

[ArmorPierce]

Problem is that evidence for other intellient life in the universe is not completely absent. Life is something that started here and there is no reason seen that it cannot occur somewhere else. Intelligent life, that is us, has resulted from evolution, therefore, there is evidence of intelligent life sprouting elsewhere in the universe.

[Stark]

Yeah, it's more like the idea of solid putty stars: there is no evidence at all that they exist, and we have no idea how one COULD exist. This absence of evidence, however, is not evidence of the absence of putty stars.

[Admiral Valdemar]

Yeah, it's more like the idea of solid putty stars: there is no evidence at all that they exist, and we have no idea how one COULD exist. This absence of evidence, however, is not evidence of the absence of putty stars.

I think people use this phrase to reassure themselves of the fact that those fantastical pixie-land things they wish were true have some possibility in being real.

Like solid putty stars.

[Sarevok]

I just response with references to the Flying Spaghetti Monster when people use this arguement to prove religon. There is no evidence the FSM exists but neither is there evidence for god. If god can exist so can the FSM. Why should the devout christian or muslim deny the FSM when he believes in god ?

I might be religious but I dont believe we can ever prove god exists and it is a matter blind fatih. It's total nonsense but on the plus side I try to encourage other religious people to recognize this and not try to prove there is scientific proof that religon is correct.