Absence of Evidence and the Evidence of Absence

In the comments section of my review of Stenger's book, a person calling himself ReallyEvilCanine raised an interesting question:


The common aphorism "Absence of evidence is [...?] evidence of absence" is the same fallacious logic used by those who believe in some deity. There's no difference between the following two versions of the Appeal to Ignorance:
* There's no evidence to disprove X, therefore X exists.
* There's no evidence to prove X, therefore X doesn't exist.


I've had this discussion before, and it can be complex. Is there evidence for Christianity or not? There is evidence. But what is it evidence of? Stenger claims science can test the evidence, and when it does, there is a lack of evidence for Christianity. Christians dispute this, of course, but Stenger makes a good case, nonetheless.

Most all of the evidence on behalf of Christianity is that science cannot explain everything, i.e., "if there's no evidence to disprove X, therefore X exists." If science cannot fully explain consciousness, the origins of morality, logic, the laws of science, and the origin of this universe itself, Christians take this as evidence that their faith is true. This is called the God of the gaps defense. God is to be found in the gaps of our knowledge.

There are twin problems for this kind of defense. One problem, as Martin Gardner explains, is that there will always be gaps in our understandings. Therefore, there will always be room for the theist to believe. The other major problem is that the believer is demanding an unreasonable standard before the evidence can actually show his faith to be wrong. The believer is demanding that the evidence must eliminate all possibility that what the believer claims is true. That's an impossible evidential standard, as I've indicated. In no other area of belief do we demand this impossible standard.

What the believer should admit is that at best, "if there's no evidence to disprove X, therefore it's possible that X exists." But you see, since there are a great many things that are possible but not actual, such a conclusion doesn't gain the believer much ground at all.

Furthermore, the scientist does not claim "if there's no evidence to prove X, therefore X doesn't exist." What he actually says is this: "if there's no evidence to prove X, therefore X probably doesn't exist." Does this appeal to ignorance in the same way as the believer does? I think not. Consider how science confirms theories. Science confirms theories based upon logical fallacies. Consider this scientific argument:

If scientific hypothesis P is true, then experiment Q will obtain.
Experiment Q obtains,
Therefore scientific hypothesis P is true.

The form of this argument is invalid. It looks like this:

P-->Q
Q
.: P

This is a fallacy called affirming the consequent, and yet that's how science proceeds for the most part when it comes to confirming hypotheses. Science doesn't prove hypotheses, even if the experiment obtains, because the hypothesis could still be false even if it does. Perhaps the experiment didn't actually test the hypothesis accurately? Perhaps premise one is a non-sequitur?

If this is true of science in general, then it becomes even more problematic when science investigates metaphysical beliefs. When it comes to these beliefs there comes a point when one person's fallacy is another person's anomally.

Think of it this way. If the claim is that the Russian government massacred 800 people in a farmland near Moscow in 1968, and there is no physical evidence that they did, what should we conclude? At that point all we have is the lone survivor's claim. Whether he is believable depends on whether we believe the tale he tells and what we think the Russian government might have done to the people he claims were killed.

What about the claim that Santa Claus or an Easter Bunny exists? What about the claim that Zeus or Apollo exists? There is no scientific evidence for such beliefs that I know of. None. So we must examine those claims pretty much the same way we would do with the claim that the Russian government killed 800 people in 1968, with an exception. We would have an additional problem with believing in so-called supernatural beings, since we have seen them come and go depending upon the culture of those who believe.

As best as I can determine it, the phrase, "absence of evidence is evidence of absence," merely describes how science operates. Science looks for evidence to support a theory. If no evidence is found for the theory, then this lack of evidence is taken to be reason to think the theory is not probable. That's all science can say, and it does it's job well.

8 comments:

Lee Randolph said...

I’m glad you brought this up. I have been wanting to say this for a while.

In an inquiry, when an argument from ignorance has investigated a domain looking for a true proposition and does not find one, then the argument from ignorance turns into an argument from knowledge.
The more you search through a knowledge base, the more you know about it until you know enough about it to say whether a given proposition is true or not.

- If I had an older brother I would know about it. Robert C. Moore calls this type of reasoning Autoepistemic Reasoning.
- I did not find my dog in my house, if he were in my house, I would have found him.

Another way to say it is as follows.
D is a domain of knowledge, K is a knowledge base in D.
It has not been established that all true propositions in D are contained in K.
A is a special type of proposition such that if A were true, A would normally or usually be expected to be in K.
A is in D.
A is not in K.
For all A in D, A is either true or false.
Therefore it is plausible to presume that A is false (subject to further investigations in D).

Walton, Douglas N. 1996. Arguments from Ignorance. Pennsylvania State University Press. P.149.

In my walk with God, I thought I found him but I was wrong. If he were there I would have found him, unless he were hiding.

Or another way to look at it is until there is evidence to support a presumption for the supernatural, the presumption for the natural has a greater weight, until there is evidence for the supernatural.
In this case, the burden of proof falls to the claimant with the least favor of presumption which would be the proponent for the supernatural.

This is defeasible, subject to reconsideration upon the presentation of new information.

Lee Randolph said...

Hi John,
I didn't have time to say everything I wanted to yesterday.
The traditional study of fallacies to some degree is a fallacy in itself.

This is a fallacy called affirming the consequent, and yet that's how science proceeds for the most part when it comes to confirming hypotheses.
At its base level Affirming the consequent is a reasoning scheme. Depending on how it is applied determines whether it is a fallacy or not. In the study of science it is a reasoning scheme correctly applied, therefore not a fallacy. Some other examples follow.
- Don’t stick you hand in the fire or you will get burned. Appeal to consequences
- Don't murder or you will go to jail. Appeal to force.
- Don’t take the stuff that has been left at the door of the charitable organization because poor people need it. Appeal to pity.
- Don't point that gun a people because it may be loaded. Appeal to ignorance.
etc…..

I didn't realize this until I read a book about informal logic. Douglas Walton and his ilk are all over this.
Here is a link to some free papers written by Walton, and here is a link to the journal of informal logic

Daniel said...

I as a believer am not looking for scientific reasons to disprove God because I know there is a God. All science proves it! I feel very sorry that you have fallen into the trap of the Devil. He rebelled against God by his free will to try and take over Heaven by attempting to prove his creation a failure by getting humans to sin and by rebelling against God while knowing him for God to be infallible we shall come to him on our own accord! That is faith and the proof of his existance is all around you and the fact that Jesus Christ was ressurected. You will remember all this in Judgement and I hope you repent before that comes!

live-n-grace said...

Well said Daniel. There is that feeling inside, undescribable, that you know there is a God. That is why so many people are religious or believe in a God because we were created to. If there really was no God, than there would be no reason that the majority of humans believe in some sort of God. Just look at the beauty of nature, a child, a fingerprint, the entire human body. Any time I study or see these things I go, wow, there is no way this could of come from nothing and by chance.

skeptic griggsy said...

Here the absence does not entail the argument from ignorance but the auto-epistemic rule that since no probable evidence will be forthcoming the absence is justified as right.

AJCSIV said...

...
You do realise that your beliefs do not match anything in biblical teachings? I can tell you where your theology dates to, in fact I'll go one step back further to get you to think about what you are saying.

The first time Satan was ever considered evil was 257 CE. Before that he was believed to be an agent of God in all respects.
Now, if we assume Moses was about 1500 {assuming he existed first and foremost}, that's exactly 1750 years of people who believe in one God who thought Satan was, wait for it, GOOD {and linguistically/biblically speaking, he is, in the same way that an angel is a messenger like your local postman}. 257 CE is exactly 1751 years from 2008, and we only went back to Moses. As an added piece, in many of the treaties against witches a witch could only use magic if Satan let them, Satan could only let them if God let him. Therefore all Satanical magic is allowed by God. Therefore, is it really evil? {Different argument, but I just thought I'd throw it in}.

Sorry, I'm a theologian, I have to do that.

As for the beauty of nature. Heck yeah, it's beautiful. Why can't it be beautiful and not require God? Why can't we conceive of beauty without God? Why can't it come from scientifically reasoned permises?

As for the internal urge that tells us God exists. That's not a very persuasive argument for anyone other than yourself, especially if they do not feel that urge. If they do not feel that urge, can you really argue that yours is truer than what they believe? What if they have a similar urge, but to Apollo? Or to Allah? Or any other deity you can name? What about that intrinsic urge that someone you know is telling you the truth, even after all evidence {including fingerprints, DNA and a voluntary confession} points the other way? Are you really justified in maintaining that belief?

Please note, I'm not trying to disuade you from HAVING a belief, if you believe that the Devil/Lucifer/Satan are the same entity {opposed by all to many literary sources including the bible} and rebelled from God etc then that's fine, but do realise that you're not actually following the same theology as those who wrote the Old and New Testaments, the leading Theologians of history from Moses to the Late Medieval/Early Renaisance period and are adhering to a common theology only developed only since the Bible was translated into English and many translation flaws were taken as cannon.

Also I must point out that evidence is first and foremost something that can be recognised as a cause for an effect. These things are empirically true. An intrinsic urge that God exists is conceptual and the only empirical thing about it is the chemical relationship occurring in your brain. This is not evidence {in the empirical sense} for God, or any other supernatural deity.

John W. Loftus said...

AJCSIV, I see you're reading through our FAQ sheet and commenting. Thanks for your comments. We read them but we cannot always respond like you'd like us to.

AJCSIV said...

Oh that's fine, I'm just longwinded and occassionally have a lot of time on my hands. Very occasionally. I just enjoy engaging in the conversation and if I say something compelling then that's just a bonus.