I really hope this doesn’t turn into a great debate, but I’m kind of curious now.
Is there anyone (save one example) that holds to the belief that lack of evidence of “x” is NOT evidence that “x” doesn’t exist?
As was pointed out in another thread, lack of evidence for “x” is not proof that x doesn’t exist, but that is different than evidence.
In real life, it would have to depend on the nature of “x”. Is “x” generally thought to be probable, possible, or impossible?
is x Baby Jesus?
Without going into the existence of deities, etc.: people have talked about things like unicorns and time travel for a long time, and I’m sure that many people have gone out of heir way to look for their existence. Isn’t lack of evidence for unicorns, or for time travel, evidence that they don’t exist?
Doesn’t matter to me where you start with your assumption about “x”.
How does the quality of “x” change the answer?
If “X” is thought to be probable (see aether, 30s) and we find no evidence for it, well, that seems to me to be evidence “x” doesn’t exist.
If “x” is thought to be possible (life on mars, 40s and 50s) and we find no evidence of it, well, that seems to me to be evidence “x” doesn’t exist.
If “x” is thought to be impossible (jumping across the grand canyon) and we find no evidence of it, well, that seems to me to be evidence “x” doesn’t exist.
Again, this isn’t proof in any scientific sense. Just evidence. The more you don’t find something, the more evidence you have about it, it seems to me.
Sure. Make x whatever you want. How does that change things?
To me, yes. But again… I’m kind of looking to see if anyone else feels differently. As I said, there is at least one person that thinks when you have no evidence for something you simply have no evidence. They seem to feel it doesn’t change anything. I disagree and wanted to get other opinions.
Absence of evidence is evidence of absence, from a strictly logical standpoint. How strong of evidence it is depends on how exhaustive the search is.
Usually, this argument comes up in nonexistence proofs. To prove something nonexistent, you need to demonstrate that it’s existence is impossible within the system you’re declaring it to be nonexistent in. This is often easy in mathematics, and sometimes even applies in the real world: we can say that a second Sol-sized sun in our inner Solar System is nonexistent because it would have to have certain physical effects that we can demonstrate are absent.
However, if mathematical, logical, or physical impossibility doesn’t apply (unicorns, supernatural anythings, aliens), then the only remaining absolute proof is to demonstrate exhaustive absence of evidence: if you’ve looked for “x” in all the possible places “x” might be and not found it, you’ve proven it’s nonexistence-using nothing but absence of evidence. On the other end of the scale, if you haven’t looked anywhere for “x”, then absence of evidence for “x” has no weight at all (I can’t even prove my roof exists without looking up).
Usually where the arguments start is evaluating how thorough the search has been. For example, I’d claim that the evidence for aliens not having visited us, abducted people, and left probes in their bodies is very, very strong based on having never found such a probe, even in people who claim to have them. A abductee believer would find all sorts of reasons why that’s logical, though, and claim that I haven’t searched nearly enough to make the statement. On the other hand, absence of evidence for the existence of aliens, anywhere, is meaningless, because we haven’t (and can’t, presently) search most of “everywhere.”
Given the relatively poor grasp many folks have of what constitutes evidence, valid scientific trial, and uses and abuses occam’s razor, arguments rarely get to this sort of subtlety effectively.
This is the heart of my question. Using the old raven analogy, if I declare that all ravens are black then you seem to be saying that until I have looked at every single raven (or looked at every single non-black object), I have no evidence at all about ravens. I tend to think that if I’ve checked all but 1 raven, and they are all black, there is evidence that the last one will be black.
---- oops… sorry…
I take back this comment. I mis-read “anywhere” for “everywhere”.
I agree, if you haven’t looked anywhere for “x” then yes, absence of evidence has no weight.
Just because you don’t find any such people doesn’t mean they don’t exist.
It depends.
If one of the characteristics of X is that it is supernatural, the absence of proof of X, may not be evidence of its non-existence.
If supernatural is not a characteristic of X, (e.g. Green one-eyed bears in North Dakota) the absence of of proof of X, may be evidence of its non-existence.
Why the differentiation for the supernatural? Suppose we start with the premise that wolverine exists. We look for evidence of this such as eyewitnesses, mangled corpses slayed by knuckle steel blades, etc. We don’t find any clues or evidence. Does it still stand that we can’t conclude anything about the existence of wolverine?
The lack of evidence is a type of evidence. One of absence. But if X is possible, than the lack of evidence for X cannot prove by itself that X doesn’t exist, only contribute to the case.
Instead of religious or supernatural overtones, think of fossil evidence with evolution. We often have “jumps” in evolutionary lines with missing links between species. The lack of evidence does not mean the evidence isn’t there. Maybe no one has unearthed it yet. The lack of evidence also does not mean that those evolutionary links never happened. Maybe no fossils have survived to this time in history. In both cases, lack of evidence does not mean X doesn’t exist.
Moving this to other supposed supernatural means, maybe there are time-traveling unicorns and the reason there is no evidence for them is because when they die their bodies dissolve into the time-stream from whence they came. The lack of evidence doesn’t mean they don’t exist; it just makes it unlikely. Thus the greater lack of evidence of X one has then the more likely X doesn’t exist. It just cannot prove it conclusively.
And cmosdes, clearly I exist or you wouldn’t be reading this.
Because “supernatural”, by definition, would seem to run counter to our understanding of nature and physics based on the evidence that we do have.
Consider the case of a murder weapon which is thrown into the middle of the ocean. Despite extensive searching the police are unable to find the weapon. Does that mean it doesn’t exist?
How about something a little more controversial, such as Bigfoot? Assuming that such a creature exists (no, I’m not saying that I’m a subscriber) and has superior vision, hearing and/or smell so that he is able to detect humans when they are far away and retreat into his cave. Can we definitely say there is no Bigfoot because no one has ever seen one?
The absence of evidence for something can definitely be used to state that there is a very high probability that it doesn’t exist, but unless you can simultaneously inspect every square inch of the world/universe, you cannot say with absolute certainty that something does not exist.
But don’t you first have to establish that the item you are seeking can exist in the first place?