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T'ai Chi · 10th December 2003, 07:41 PM

Is absence of evidence the same as evidence of absence?

Some people here think it is, but others disagree.

Who is correct?

ImpyTimpy · 10th December 2003, 07:45 PM

Quote:

Originally posted by T'ai Chi
Is absence of evidence the same as evidence of absence?

Some people here think it is, but others disagree.

Who is correct?

To say that if something lacks evidence, it does not exist is to commit a clear-cut logical fallacy.

To say lack of evidence of something suggests it may not be possible/it may not exist is to use common sense.

plindboe · 10th December 2003, 08:06 PM

Ugh, this is a tough one. Evidence is not proof, so even though there is evidence for something, doesn't neccessarily make it true.

I would say that absence of evidence is evidence of absence, but weak evidence, and not conclusive evidence in any way.

If a murder investigation can come up with no evidence at all that the suspect is guilty, then this fact alone increases the chance that he is innocent, thereby it is a form of evidence.

Yahweh · 10th December 2003, 08:51 PM

I'm a little out in the dark as to how you find empirical evidence (much less proof) to demonstrate the non-existence of something...

thaiboxerken · 10th December 2003, 09:00 PM

Quote:

Originally posted by Yahweh
I'm a little out in the dark as to how you find empirical evidence (much less proof) to demonstrate the non-existence of something...

I think, according to woo-wooism and Tai Chi, that you can't ever prove the non-existence of something. Therefore, according to them, everything may exist and every claim is worth investigating. Except for invisible, blue, intangible smurfs.. for some unknown reason.

ImpyTimpy · 11th December 2003, 03:40 PM

Quote:

Originally posted by thaiboxerken

I think, according to woo-wooism and Tai Chi, that you can't ever prove the non-existence of something. Therefore, according to them, everything may exist and every claim is worth investigating. Except for invisible, blue, intangible smurfs.. for some unknown reason.

You know, you're actually sort of correct there. Of course, the possibility is that everything may exist. Science has this cool theory that states there may be lots of different universes around with very different laws and mathematical equations to describe them. I don't remember what is the name of it though (starts with a I think).

Whether these things are worth investigating or not is another idea.

Yahweh · 11th December 2003, 04:05 PM

Quote:

Originally posted by ImpyTimpy
You know, you're actually sort of correct there. Of course, the possibility is that everything may exist. Science has this cool theory that states there may be lots of different universes around with very different laws and mathematical equations to describe them. I don't remember what is the name of it though (starts with a I think).

String Theory.

(The one with 10 spatial dimensions, 1 temporal dimension, branes, and lots of fun exotic particles like s_particles...)

Stereolab · 11th December 2003, 04:06 PM

Quote:

Originally posted by thaiboxerken

I think, according to woo-wooism and Tai Chi, that you can't ever prove the non-existence of something. Therefore, according to them, everything may exist and every claim is worth investigating. Except for invisible, blue, intangible smurfs.. for some unknown reason.

It's funny how completely clueless you are, and how you're totally oblivious to that fact.

If you were more intelligent, and more of a skeptic, you'd realize that you don't know nearly as much as you think you do.

thaiboxerken · 11th December 2003, 04:17 PM

It's funny how completely clueless you are, and how you're totally oblivious to that fact.

You mean.. I don't believe in the paranormal, so I must be clueless, right?

Absence of evidence IS evidence of absence.. it's not conclusive, but it's highly suggestive.

If you were more intelligent, and more of a skeptic, you'd realize that you don't know nearly as much as you think you do.

You really don't like me, do you?

Nyarlathotep · 11th December 2003, 04:20 PM

It is more complicated thatn a simple yes or no.

Put into a short form my answer boils down to: no it is not evidence of absence but that doesn't mean much of anything. In the absence of hard evidence,if one is going to speculateon the existance of something, one then has to look at other things, such as how likely the thing is to exist, whether its existance contradicts the laws of the universe as you know them, etc.

So if I claim that I have a Cousin Ruth, but you have never met her nor met anyone who has (i.e. you have no evidence that she exists) you can safely act on the assumption that she does since her existance isn't unlikely and is probably trivial. If I clalm that my Cousin Ruth can fly by flapping her arms, then it changes. Since youhave no evidence you can't say 100% that I am blowing smoke, but since someone flying by flapping their arms contradicts the laws of physics, it would not be wise to assume that I am telling the truth.

It's oversimplified, to be sure, but that is how I look at things.

Flatworm · 11th December 2003, 05:19 PM

Absence of evidence is not evidence of absence.

However, lack of disproof is not a sufficient condition for making an idea worthy of serious consideration.

gentlehorse · 11th December 2003, 06:08 PM

Quote:

Originally posted by thaiboxerken
I think, according to woo-wooism and Tai Chi, that you can't ever prove the non-existence of something. Therefore, according to them, everything may exist and every claim is worth investigating.

Where did Tai Chi say that every claim is worth investigating? You wouldn't be putting words in another's mouth, would you Ken? Is this your idea of presenting, or laying the foundation for, a rational argument? Surely not--

Of course, this kind of response is in keeping with your MO. I don't know why I would expect anything different of you. My bad--

Paul C. Anagnostopoulos · 11th December 2003, 06:26 PM

Quote:

Is absence of evidence the same as evidence of absence?

My, this is difficult. Are we talking about complete and utter absence of evidence? If so, that's pretty good evidence of absence. Either that, or the thing we're looking for exists, but leaves no evidence. In which case, . . . well, you know the drill.

~~ Paul

69dodge · 11th December 2003, 07:00 PM

Quote:

Originally posted by T'ai Chi
Is absence of evidence the same as evidence of absence?

Depends.

How easy would finding evidence of it be, if it were present?

How hard did you look for evidence of it, before giving up?

T'ai Chi · 11th December 2003, 07:00 PM

Quote:

Originally posted by thaiboxerken

I think, according to woo-wooism and Tai Chi, that you can't ever prove the non-existence of something. Therefore, according to them, everything may exist and every claim is worth investigating. Except for invisible, blue, intangible smurfs.. for some unknown reason.

Yawn.

Universal negatives maybe (because you have to search all of time and space, and last time I checked, that was pretty hard), but not any other negatives.

!Xx+-Rational-+xX! · 11th December 2003, 07:27 PM

Anything that skeptics don't agree with should be considered impossible! This means there can never be evidence nomatter what woo-woos say! Or else science will be destroyed! We were put here with the elite mission by natural selection to put an end to quackery!

11th December 2003, 07:33 PM

If there is no evidence that a certain thing exists, we can assume that it exists for the purposes of hypothesis and experimentation, but if repeated experimentation and/or observation fails to show evidence that the thing exists, we can be fairly certain that it just ain't there.

One must be careful not to fall into the trap of thinking that because there is no evidence that something does not exist, that it might exist.

Personally, I've come to the conclusion that a lot of things just ain't there. I won't worry about them unless they turn up. In the meantime, I have far more important and very real things to deal with. For now, ESP and other nonsense is a waste of my valuable time.

Upchurch · 11th December 2003, 07:42 PM

Strictly speaking, no. Absence of evidence is a indicator of absence, but it is not absolute evidence of absence.

ImpyTimpy · 11th December 2003, 08:20 PM

Quote:

Originally posted by Ohrryp
If there is no evidence that a certain thing exists, we can assume that it exists for the purposes of hypothesis and experimentation, but if repeated experimentation and/or observation fails to show evidence that the thing exists, we can be fairly certain that it just ain't there.

I have to respectfully disagree there with you. If anything, I believe it may also show us that perhaps our experimentation methods are incorrect. As long as something is plausible and we may have a benefit in discovering it's existence, we should keep looking for it. If our repeated experiments fail to discover it, it does not automatically mean what we look for doesn't exist, it could mean our experimentation method may be flawed.

Quote:

One must be careful not to fall into the trap of thinking that because there is no evidence that something does not exist, that it might exist.

That's true and I think some believers try and use this argument to support their beliefs. It's a very irrational argument but relative irrationality of something hasn't stopped people from carrying on with it.

Quote:

Personally, I've come to the conclusion that a lot of things just ain't there. I won't worry about them unless they turn up. In the meantime, I have far more important and very real things to deal with. For now, ESP and other nonsense is a waste of my valuable time.

I agree to an extent, that is I think we shouldn't abandon the possibility of these things existing, hence we've got people who try and research these things. However, just because something might exist doesn't mean it does. Still, what if it did? I believe that may be what drives these people to try and discover the paranormal and I see no problem with that. I do have a problem with unfounded beliefs though.

espritch · 11th December 2003, 09:20 PM

Absence of evidence is evidence of abscence. It may not, however, be conclusive evidence.

T'ai Chi · 11th December 2003, 09:21 PM

Quote:

Originally posted by Ohrryp
If there is no evidence that a certain thing exists, we can assume that it exists for the purposes of hypothesis and experimentation, but if repeated experimentation and/or observation fails to show evidence that the thing exists, we can be fairly certain that it just ain't there.

So no extra-terrestrials exist?

Are you fairly certain?

apoger · 11th December 2003, 09:36 PM

T'ai Chi, after reading this thread and a bunch of your other posts it seems apparent that you are making the mistake of equating "evidence" with "absolute proof".

Evidence is always modified by a confidence level, and is never absolute.

Walter Wayne · 11th December 2003, 09:37 PM

Absence of evidence is evidence of absence when a search has been carried out that would almost certainly uncover evidence.

Quote:

Originally posted by Ohrryp
If there is no evidence that a certain thing exists, we can assume that it exists for the purposes of hypothesis and experimentation, but if repeated experimentation and/or observation fails to show evidence that the thing exists, we can be fairly certain that it just ain't there.

Originally posted by T'ai Chi
So no extra-terrestrials exist?

Are you fairly certain?

In this case, while the existence of extra-terrestials would leave evidence (it is testable), we have not made a search that would be likely to uncover said evidence. So in this case, evidence of absence is evidence of an inability to carry out a reasonable experiment to test the hypothesis.

Walt

Charlie in Dayton · 12th December 2003, 01:26 AM

Quote:

Originally posted by Flatworm
Absence of evidence is not evidence of absence.

However, lack of disproof is not a sufficient condition for making an idea worthy of serious consideration.

Flatworm, I've saved your quote in my archives (with appropriate credit). I'm going to cogitate on that statement awhile...I immediately found it to be profound, and worthy of deep consideration. Somehow, I feel there's the seeds of an essay there.

Excellent turn of phrase.

After suitable consideration, I nominated it for the December Language Award.

Hazelip · 12th December 2003, 02:36 AM

What evidence does is support the reasonableness of a conclusion. If there is sufficient evidence for something, then it is reasonable to conclude that the particular something does exist. If there is no evidence to support a claim, then it may be reasonable to conclude that the particular claim is false, or that the thing does not exist. But, not in every situation.

Go search Cartesian Logic.

Darat · 12th December 2003, 04:25 AM

T'ai Chi - Just thinking this through.

There is no evidence that I shot JFK so I take it that it would be wrong for someone to say "There is no evidence that Darat shot JFK therefore Darat didn't shoot JFK"?

LTC8K6 · 12th December 2003, 05:35 AM

Well "absence of evidence" means no evidence at all to me.

It seems to me that a reasonable person could take that as an absolute.

However, you can't say there is an "absence of evidence" in many situations, so the answer would vary.

If the "absence of evidence" is a certainty, if the evidence would be obvious and it just isn't there, then a reasonable person could conclude that that equals "evidence of absence".

Of course the "absence of evidence" can change tomorrow.

pgwenthold · 12th December 2003, 06:13 AM

Absense of evidence where evidence should be is evidence of absense.

For example, there is no evidence that there is an elephant in my office. If there were an elephant in my office, I should expect to find certain indicators, such as big piles of dung. The lack of dung is evidence that there is not an elephant in my office.

If you think of it in terms of a hypothesis, then it makes sense. Hypotheses lead to predictions. If those predictions are not borne out, then that is evidence against the hypothesis.

Skeptical Greg · 12th December 2003, 06:42 AM

I would say an absence of evidence is a clear indication of no evidence..

Evidence for what ?

Zero · 12th December 2003, 12:44 PM

Absence of evidence, whatever else it is, is not a licence to believe or promote any and every crackpot idea that comes along.

RichardR · 12th December 2003, 05:24 PM

Yes – if you have looked for that evidence and not found any.

However, it is not proof of absence.

12th December 2003, 05:46 PM

Quote:

Originally posted by T'ai Chi
So no extra-terrestrials exist?

Are you fairly certain?

Yup. I'm fairly certain that no extra-terrestrials exist.

However, I accept the possibility that I could be mistaken.

espritch · 12th December 2003, 08:48 PM

Quote:

So no extra-terrestrials exist?

Are you fairly certain?

Let me put it this way. I am fairly certain that no Martians exist. We've sent probes and there was a distinct lack of evidence found (at least in the classic little green man sense). In this case abscence of evidence is pretty good evidence of abscence. Or do you think maybe there are little green men on Mars?

Obviously, I can't make any assumption about extra-terrestrials beyond our solar system since we currently have no means to look for conclusive evidence. There is a difference between failure to find evidence and inability to look for it.

!Xx+-Rational-+xX! · 12th December 2003, 09:55 PM

Skeptics are always right and any evidence that threatens this is false!

Yahweh · 14th December 2003, 01:36 PM

T'ai Chi, your current avatar is a little distracting. Here is the same image, it rotates smoother, its only 6,319 bytes (avatars can be up to 7000 bytes).

This GIF is compiled from 21 individual frames, the framerate is ~.04 per second. That means the amount of time for the Yin Yang to make one revolution is ~every .84 seconds (actually, the transition between frames will be slower depending on the speed of your processor... on most computers, the image will appear to rotate a bit slower than once per .84 seconds).

Jeff Corey · 14th December 2003, 02:12 PM

Quote:

Originally posted by Ohrryp
If there is no evidence that a certain thing exists, we can assume that it exists for the purposes of hypothesis and experimentation, but if repeated experimentation and/or observation fails to show evidence that the thing exists, we can be fairly certain that it just ain't there.

One must be careful not to fall into the trap of thinking that because there is no evidence that something does not exist, that it might exist.

Personally, I've come to the conclusion that a lot of things just ain't there. I won't worry about them unless they turn up. In the meantime, I have far more important and very real things to deal with. For now, ESP and other nonsense is a waste of my valuable time.

I fully agree, but I still have some time to waste investigating weird claims. Maybe even writing them up for Claus.
Maybe,

CFLarsen · 14th December 2003, 02:41 PM

Quote:

Originally posted by Jeff Corey

I fully agree, but I still have some time to waste investigating weird claims. Maybe even writing them up for Claus.
Maybe,

I'll take that as being affirmative.

Deadline's the 28th, six-eyes.

T'ai Chi · 14th December 2003, 03:08 PM

Quote:

Originally posted by Yahweh
T'ai Chi, your current avatar is a little distracting. Here is the same image, it rotates smoother, its only 6,319 bytes (avatars can be up to 7000 bytes).

This GIF is compiled from 21 individual frames, the framerate is ~.04 per second. That means the amount of time for the Yin Yang to make one revolution is ~every .84 seconds (actually, the transition between frames will be slower depending on the speed of your processor... on most computers, the image will appear to rotate a bit slower than once per .84 seconds).

Sweeet. Thanks Yahweh.

Now one question. How do I get that animated icon to be my new avatar? I do a 'Open image in new window' and I am getting some .php file

instead of a .gif; probably something on my end.

Craig · 14th December 2003, 03:15 PM

You know, that slower yin-yang is strangely hypnotic to watch.

Incidentally, I've got the urge to send all of my money to Yahweh...

Yahweh · 14th December 2003, 03:50 PM

Quote:

Originally posted by T'ai Chi
Sweeet. Thanks Yahweh.

Now one question. How do I get that animated icon to be my new avatar? I do a 'Open image in new window' and I am getting some .php file instead of a .gif; probably something on my end.

The reason you are getting a .php file is because this software stores binary files in a database. This isnt the same as storing it locally on a server. Because the binary information is stored in the database, the SRC attribute of the IMG tag has to link to a .php file rather than a GIF file. The PHP file is a script which reads the binary information from the database.

I've stored the image on a VillagePhotos.com server.

If you want to change your avatar, you can go to User Control Panel - Edit Avatar. The URL of the image is stored at:
http://img.villagephotos.com/p/2003-...nYangSpin1.gif

As a wise and valiant upholder of justice and truth, I choose corn.	12	23.08%
As a perverter of all that is beautiful in the universe, I choose flour.	16	30.77%
As an ecumenical spineless feel-good wimp, I like them both.	14	26.92%
I do not like either, and plead my neutrality, which I realise is just as wimpy as liking both.	1	1.92%
This poll is too biased for me to vote in, as I am quite possibly the wimpiest carbon-based lifeform imaginable.	1	1.92%
On, Planet X, all tortillas are made from ground bone-meal.	8	15.38%
Voters: 52. You may not vote on this poll

10th December 2003, 07:41 PM	#1
T'ai Chi Penultimate Amazing Join Date: May 2003 Posts: 11,235	Absence of evidence = evidence of absence? Is absence of evidence the same as evidence of absence? Some people here think it is, but others disagree. Who is correct?
	__________________ http://www.statisticool.com

10th December 2003, 07:45 PM	#2
ImpyTimpy Muse Join Date: Jul 2002 Posts: 803	Re: Absence of evidence = evidence of absence? Quote: Originally posted by T'ai Chi Is absence of evidence the same as evidence of absence? Some people here think it is, but others disagree. Who is correct? To say that if something lacks evidence, it does not exist is to commit a clear-cut logical fallacy. To say lack of evidence of something suggests it may not be possible/it may not exist is to use common sense.
ImpyTimpy Muse Join Date: Jul 2002 Posts: 803	__________________ "You are a bunch of kook haters and a hate-group. " - the now gone Jedi Knight describing the board's attitude to dangerous and out of this world ideas.

10th December 2003, 08:06 PM	#3
plindboe Graduate Poster Join Date: Apr 2003 Location: Denmark Posts: 1,244	Ugh, this is a tough one. Evidence is not proof, so even though there is evidence for something, doesn't neccessarily make it true. I would say that absence of evidence is evidence of absence, but weak evidence, and not conclusive evidence in any way. If a murder investigation can come up with no evidence at all that the suspect is guilty, then this fact alone increases the chance that he is innocent, thereby it is a form of evidence.
	__________________ Peter "The whole problem with the world is that fools and fanatics are always so certain of themselves, but wiser people so full of doubts." (Bertrand Russell)

10th December 2003, 08:51 PM	#4
Yahweh Ayay ashay ayay Join Date: Apr 2003 Posts: 9,029	I'm a little out in the dark as to how you find empirical evidence (much less proof) to demonstrate the non-existence of something...
Yahweh Ayay ashay ayay Join Date: Apr 2003 Posts: 9,029

10th December 2003, 09:00 PM	#5
thaiboxerken Penultimate Amazing Join Date: Sep 2001 Location: Portland, Oregon Posts: 21,076	Quote: Originally posted by Yahweh I'm a little out in the dark as to how you find empirical evidence (much less proof) to demonstrate the non-existence of something... I think, according to woo-wooism and Tai Chi, that you can't ever prove the non-existence of something. Therefore, according to them, everything may exist and every claim is worth investigating. Except for invisible, blue, intangible smurfs.. for some unknown reason.
	__________________ All national institutions of churches, whether Jewish, Christian or Turkish, appear to me no other than human inventions, set up to terrify and enslave mankind, and monopolize power & profit - Thomas Paine

11th December 2003, 03:40 PM	#6
ImpyTimpy Muse Join Date: Jul 2002 Posts: 803	Quote: Originally posted by thaiboxerken I think, according to woo-wooism and Tai Chi, that you can't ever prove the non-existence of something. Therefore, according to them, everything may exist and every claim is worth investigating. Except for invisible, blue, intangible smurfs.. for some unknown reason. You know, you're actually sort of correct there. Of course, the possibility is that everything may exist. Science has this cool theory that states there may be lots of different universes around with very different laws and mathematical equations to describe them. I don't remember what is the name of it though (starts with a I think). Whether these things are worth investigating or not is another idea.
ImpyTimpy Muse Join Date: Jul 2002 Posts: 803	__________________ "You are a bunch of kook haters and a hate-group. " - the now gone Jedi Knight describing the board's attitude to dangerous and out of this world ideas.

11th December 2003, 04:05 PM	#7
Yahweh Ayay ashay ayay Join Date: Apr 2003 Posts: 9,029	Quote: Originally posted by ImpyTimpy You know, you're actually sort of correct there. Of course, the possibility is that everything may exist. Science has this cool theory that states there may be lots of different universes around with very different laws and mathematical equations to describe them. I don't remember what is the name of it though (starts with a I think). String Theory. (The one with 10 spatial dimensions, 1 temporal dimension, branes, and lots of fun exotic particles like s_particles...)
Yahweh Ayay ashay ayay Join Date: Apr 2003 Posts: 9,029

11th December 2003, 04:06 PM	#8
Stereolab Massager of French Join Date: Jul 2002 Posts: 3,372	Quote: Originally posted by thaiboxerken I think, according to woo-wooism and Tai Chi, that you can't ever prove the non-existence of something. Therefore, according to them, everything may exist and every claim is worth investigating. Except for invisible, blue, intangible smurfs.. for some unknown reason. It's funny how completely clueless you are, and how you're totally oblivious to that fact. If you were more intelligent, and more of a skeptic, you'd realize that you don't know nearly as much as you think you do.

11th December 2003, 04:17 PM	#9
thaiboxerken Penultimate Amazing Join Date: Sep 2001 Location: Portland, Oregon Posts: 21,076	It's funny how completely clueless you are, and how you're totally oblivious to that fact. You mean.. I don't believe in the paranormal, so I must be clueless, right? Absence of evidence IS evidence of absence.. it's not conclusive, but it's highly suggestive. If you were more intelligent, and more of a skeptic, you'd realize that you don't know nearly as much as you think you do. You really don't like me, do you?
	__________________ All national institutions of churches, whether Jewish, Christian or Turkish, appear to me no other than human inventions, set up to terrify and enslave mankind, and monopolize power & profit - Thomas Paine

11th December 2003, 04:20 PM	#10
Nyarlathotep Philosopher Join Date: Mar 2003 Posts: 7,514	It is more complicated thatn a simple yes or no. Put into a short form my answer boils down to: no it is not evidence of absence but that doesn't mean much of anything. In the absence of hard evidence,if one is going to speculateon the existance of something, one then has to look at other things, such as how likely the thing is to exist, whether its existance contradicts the laws of the universe as you know them, etc. So if I claim that I have a Cousin Ruth, but you have never met her nor met anyone who has (i.e. you have no evidence that she exists) you can safely act on the assumption that she does since her existance isn't unlikely and is probably trivial. If I clalm that my Cousin Ruth can fly by flapping her arms, then it changes. Since youhave no evidence you can't say 100% that I am blowing smoke, but since someone flying by flapping their arms contradicts the laws of physics, it would not be wise to assume that I am telling the truth. It's oversimplified, to be sure, but that is how I look at things.
	__________________ Why stay sane in a sick world?

11th December 2003, 05:19 PM	#11
Flatworm Thinker Join Date: Sep 2001 Location: New Boston, MI Posts: 157	Absence of evidence is not evidence of absence. However, lack of disproof is not a sufficient condition for making an idea worthy of serious consideration.
	__________________ Some people don't suffer fools gladly. Others suffer fools as a form of recreation.

11th December 2003, 06:08 PM	#12
gentlehorse generally confused Join Date: Aug 2001 Posts: 2,147	Quote: Originally posted by thaiboxerken I think, according to woo-wooism and Tai Chi, that you can't ever prove the non-existence of something. Therefore, according to them, everything may exist and every claim is worth investigating. Where did Tai Chi say that every claim is worth investigating? You wouldn't be putting words in another's mouth, would you Ken? Is this your idea of presenting, or laying the foundation for, a rational argument? Surely not-- Of course, this kind of response is in keeping with your MO. I don't know why I would expect anything different of you. My bad--
	__________________ "Oh Holy gravity, the mother of all powers, what you do to us, the children of the stars" pillory "How can the third-person requirements of the scientific method be reconciled with the first-person nature of consciousness?" Win

11th December 2003, 06:26 PM	#13
Paul C. Anagnostopoulos Nap, interrupted. Join Date: Aug 2001 Location: a little toolshed Posts: 18,631	Quote: Is absence of evidence the same as evidence of absence? My, this is difficult. Are we talking about complete and utter absence of evidence? If so, that's pretty good evidence of absence. Either that, or the thing we're looking for exists, but leaves no evidence. In which case, . . . well, you know the drill. ~~ Paul
	__________________ Millions long for immortality who do not know what to do with themselves on a rainy Sunday afternoon. ---Susan Ertz RIP Mr. Skinny

11th December 2003, 07:00 PM	#14
69dodge Illuminator Join Date: Nov 2002 Posts: 3,607	Re: Absence of evidence = evidence of absence? Quote: Originally posted by T'ai Chi Is absence of evidence the same as evidence of absence? Depends. How easy would finding evidence of it be, if it were present? How hard did you look for evidence of it, before giving up?
69dodge Illuminator Join Date: Nov 2002 Posts: 3,607

11th December 2003, 07:27 PM	#16
!Xx+-Rational-+xX! ! skeptiscientisuperioristism Join Date: Aug 2003 Posts: 876	Anything that skeptics don't agree with should be considered impossible! This means there can never be evidence nomatter what woo-woos say! Or else science will be destroyed! We were put here with the elite mission by natural selection to put an end to quackery!

11th December 2003, 07:33 PM	#17
Paladin Guest Posts: n/a	If there is no evidence that a certain thing exists, we can assume that it exists for the purposes of hypothesis and experimentation, but if repeated experimentation and/or observation fails to show evidence that the thing exists, we can be fairly certain that it just ain't there. One must be careful not to fall into the trap of thinking that because there is no evidence that something does not exist, that it might exist. Personally, I've come to the conclusion that a lot of things just ain't there. I won't worry about them unless they turn up. In the meantime, I have far more important and very real things to deal with. For now, ESP and other nonsense is a waste of my valuable time.
Paladin Guest Posts: n/a

11th December 2003, 07:42 PM	#18
Upchurch Papa Funkosophy Join Date: May 2002 Location: Funky Town (STL, MO) Posts: 23,472	Strictly speaking, no. Absence of evidence is a indicator of absence, but it is not absolute evidence of absence.

11th December 2003, 08:20 PM	#19
ImpyTimpy Muse Join Date: Jul 2002 Posts: 803	Quote: Originally posted by Ohrryp If there is no evidence that a certain thing exists, we can assume that it exists for the purposes of hypothesis and experimentation, but if repeated experimentation and/or observation fails to show evidence that the thing exists, we can be fairly certain that it just ain't there. I have to respectfully disagree there with you. If anything, I believe it may also show us that perhaps our experimentation methods are incorrect. As long as something is plausible and we may have a benefit in discovering it's existence, we should keep looking for it. If our repeated experiments fail to discover it, it does not automatically mean what we look for doesn't exist, it could mean our experimentation method may be flawed. Quote: One must be careful not to fall into the trap of thinking that because there is no evidence that something does not exist, that it might exist. That's true and I think some believers try and use this argument to support their beliefs. It's a very irrational argument but relative irrationality of something hasn't stopped people from carrying on with it. Quote: Personally, I've come to the conclusion that a lot of things just ain't there. I won't worry about them unless they turn up. In the meantime, I have far more important and very real things to deal with. For now, ESP and other nonsense is a waste of my valuable time. I agree to an extent, that is I think we shouldn't abandon the possibility of these things existing, hence we've got people who try and research these things. However, just because something might exist doesn't mean it does. Still, what if it did? I believe that may be what drives these people to try and discover the paranormal and I see no problem with that. I do have a problem with unfounded beliefs though.
ImpyTimpy Muse Join Date: Jul 2002 Posts: 803	__________________ "You are a bunch of kook haters and a hate-group. " - the now gone Jedi Knight describing the board's attitude to dangerous and out of this world ideas.

11th December 2003, 09:20 PM	#20
espritch Graduate Poster Join Date: Jul 2002 Posts: 1,380	Absence of evidence is evidence of abscence. It may not, however, be conclusive evidence.
	__________________ "I'm the master of low expectations." - G. W. Bush

11th December 2003, 09:21 PM	#21
T'ai Chi Penultimate Amazing Join Date: May 2003 Posts: 11,235	Quote: Originally posted by Ohrryp If there is no evidence that a certain thing exists, we can assume that it exists for the purposes of hypothesis and experimentation, but if repeated experimentation and/or observation fails to show evidence that the thing exists, we can be fairly certain that it just ain't there. So no extra-terrestrials exist? Are you fairly certain?
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11th December 2003, 09:36 PM	#22
apoger Muse Join Date: Oct 2001 Posts: 563	T'ai Chi, after reading this thread and a bunch of your other posts it seems apparent that you are making the mistake of equating "evidence" with "absolute proof". Evidence is always modified by a confidence level, and is never absolute.
apoger Muse Join Date: Oct 2001 Posts: 563

11th December 2003, 09:37 PM	#23
Walter Wayne Wayne's Words Join Date: Jul 2002 Location: Ottawa, ON Posts: 2,450	Absence of evidence is evidence of absence when a search has been carried out that would almost certainly uncover evidence. Quote: Originally posted by Ohrryp If there is no evidence that a certain thing exists, we can assume that it exists for the purposes of hypothesis and experimentation, but if repeated experimentation and/or observation fails to show evidence that the thing exists, we can be fairly certain that it just ain't there. Originally posted by T'ai Chi So no extra-terrestrials exist? Are you fairly certain? In this case, while the existence of extra-terrestials would leave evidence (it is testable), we have not made a search that would be likely to uncover said evidence. So in this case, evidence of absence is evidence of an inability to carry out a reasonable experiment to test the hypothesis. Walt

12th December 2003, 01:26 AM	#24
Charlie in Dayton Rabid radioactive stargazer and JREF kid Join Date: Aug 2001 Posts: 1,087	Quote: Originally posted by Flatworm Absence of evidence is not evidence of absence. However, lack of disproof is not a sufficient condition for making an idea worthy of serious consideration. Flatworm, I've saved your quote in my archives (with appropriate credit). I'm going to cogitate on that statement awhile...I immediately found it to be profound, and worthy of deep consideration. Somehow, I feel there's the seeds of an essay there. Excellent turn of phrase. After suitable consideration, I nominated it for the December Language Award.
	__________________ "If a tree is cut down in the rainforest, and is used to make paper to print a book, and the book is really bad, and there's nobody that will read it, do you still hear a sucking sound?" Charlie in Dayton

12th December 2003, 02:36 AM	#25
Hazelip Critical Thinker Join Date: Dec 2002 Posts: 497	What evidence does is support the reasonableness of a conclusion. If there is sufficient evidence for something, then it is reasonable to conclude that the particular something does exist. If there is no evidence to support a claim, then it may be reasonable to conclude that the particular claim is false, or that the thing does not exist. But, not in every situation. Go search Cartesian Logic.
Hazelip Critical Thinker Join Date: Dec 2002 Posts: 497	__________________ Boring blog: http://www.Hazelip.com/

12th December 2003, 04:25 AM	#26
Darat Lackey Administrator / JREF Forum Liaison Join Date: Aug 2001 Location: South East, UK Posts: 64,985	T'ai Chi - Just thinking this through. There is no evidence that I shot JFK so I take it that it would be wrong for someone to say "There is no evidence that Darat shot JFK therefore Darat didn't shoot JFK"?
	__________________ If it were all so simple! If only there were evil people somewhere insidiously committing evil deeds, and it were necessary only to separate them from the rest of us and destroy them. But the line dividing good and evil cuts through the heart of every human being. And who is willing to destroy a piece of his own heart? - Aleksandr Solzhenitsyn 1918-2008

12th December 2003, 05:35 AM	#27
LTC8K6 Penultimate Amazing Join Date: Nov 2002 Location: Directly under a deadly chemtrail Posts: 12,755	Well "absence of evidence" means no evidence at all to me. It seems to me that a reasonable person could take that as an absolute. However, you can't say there is an "absence of evidence" in many situations, so the answer would vary. If the "absence of evidence" is a certainty, if the evidence would be obvious and it just isn't there, then a reasonable person could conclude that that equals "evidence of absence". Of course the "absence of evidence" can change tomorrow.

12th December 2003, 06:13 AM	#28
pgwenthold Penultimate Amazing Join Date: Sep 2001 Posts: 12,119	Absense of evidence where evidence should be is evidence of absense. For example, there is no evidence that there is an elephant in my office. If there were an elephant in my office, I should expect to find certain indicators, such as big piles of dung. The lack of dung is evidence that there is not an elephant in my office. If you think of it in terms of a hypothesis, then it makes sense. Hypotheses lead to predictions. If those predictions are not borne out, then that is evidence against the hypothesis.
	__________________ "Baseball is a philosophy. The primordial ooze that once ruled our world has been captured in perpetual motion. Baseball is the moment. Its ever changing patterns are hypnotizing yet invigorating. Baseball is an art form. Classic and at the same time...progressive. Baseball is pre-historic and post-modern. Baseball is here to stay." (Stolen from the side of a lava lamp box, and modified slightly)

12th December 2003, 06:42 AM	#29
Skeptical Greg Agave Wine Connoisseur Join Date: Jul 2002 Location: Just past 'Resume Speed' Posts: 12,892	I would say an absence of evidence is a clear indication of no evidence.. Evidence for what ?
	__________________ " Somewhere between Jesus dying on the cross, and a giant bunny hiding eggs,there seems to be a gap in information. " Stan - Southpark Prove your computer is not a wimp ! Join the JREF Folders ! Team 13232

12th December 2003, 12:44 PM	#30
Zero Graduate Poster Join Date: Dec 2003 Posts: 1,535	Absence of evidence, whatever else it is, is not a licence to believe or promote any and every crackpot idea that comes along.
Zero Graduate Poster Join Date: Dec 2003 Posts: 1,535

12th December 2003, 05:24 PM	#31
RichardR Join Date: Nov 2001 Posts: 2,281	Yes – if you have looked for that evidence and not found any. However, it is not proof of absence.
RichardR Join Date: Nov 2001 Posts: 2,281

12th December 2003, 05:46 PM	#32
Paladin Guest Posts: n/a	Quote: Originally posted by T'ai Chi So no extra-terrestrials exist? Are you fairly certain? Yup. I'm fairly certain that no extra-terrestrials exist. However, I accept the possibility that I could be mistaken.
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12th December 2003, 08:48 PM	#33
espritch Graduate Poster Join Date: Jul 2002 Posts: 1,380	Quote: So no extra-terrestrials exist? Are you fairly certain? Let me put it this way. I am fairly certain that no Martians exist. We've sent probes and there was a distinct lack of evidence found (at least in the classic little green man sense). In this case abscence of evidence is pretty good evidence of abscence. Or do you think maybe there are little green men on Mars? Obviously, I can't make any assumption about extra-terrestrials beyond our solar system since we currently have no means to look for conclusive evidence. There is a difference between failure to find evidence and inability to look for it.
	__________________ "I'm the master of low expectations." - G. W. Bush

12th December 2003, 09:55 PM	#34
!Xx+-Rational-+xX! ! skeptiscientisuperioristism Join Date: Aug 2003 Posts: 876	Skeptics are always right and any evidence that threatens this is false!

14th December 2003, 01:36 PM	#35
Yahweh Ayay ashay ayay Join Date: Apr 2003 Posts: 9,029	T'ai Chi, your current avatar is a little distracting. Here is the same image, it rotates smoother, its only 6,319 bytes (avatars can be up to 7000 bytes). This GIF is compiled from 21 individual frames, the framerate is ~.04 per second. That means the amount of time for the Yin Yang to make one revolution is ~every .84 seconds (actually, the transition between frames will be slower depending on the speed of your processor... on most computers, the image will appear to rotate a bit slower than once per .84 seconds).
Yahweh Ayay ashay ayay Join Date: Apr 2003 Posts: 9,029