Friday, June 10, 2016

The XYZ question concerning evidence

It goes like this. X is evidence for Y just in case Z.

I've answered the question here at various times, and people are dissatisfied with my answer. Fine. I want to know your XYZ answer. If you are going to tell me I don't have any evidence, then apparently you have a different answer to the XYZ question than I do. But when I ask people what their answer is, I never find out.

29 comments:

Cal Metzger said...

VR: "But when I ask people what their answer is, I never find out."

?!?!?

For the umpteenth time, evidence is something that is examinable -- something that can be "checked out" in ways that are objective, reliable, and verifiable.

And evidence isn't "some" piece (X) stripped away and isolated from the rest of the information, a part taken away to be viewed in isolation, and it's not "owned" by a case Z (it could belong to a case E, which would be a better explanation for it and all the other evicence.

Evidence is ALL the relevant data together, as its coalesced into something that is viewed and understood by rival explanations.

entirelyuseless said...

Cal has argued on Loftus's blog that Z here should include, "and I think that Y is true." That is, he will not admit the existence of evidence for anything that overall he believes to be false.

Victor Reppert said...

Well, it seems clear to me that there can be pieces of evidence for things that may turn out not to be true. There is also evidence that is not currently available. For example, my fingerprints on the murder weapon is evidence that I committed the murder even if the total evidence suggests that someone else did it. Also, is it neither true nor false that there is life on other planets similar in intelligence to our own? There may be evidence out there, but I haven't seen it either way.

If "there is no evidence" just means "the preponderance of the evidence, on my view, goes the other way," then it is easy to see how a rational person can believe all sorts of things for which there is no evidence. The no evidence claim amounts, in that instance to very little.

Finally, if one disciple says "I saw the risen Jesus," and a second one says "I did, too," doesn't that means the evidence can be, and was, checked, and therefore Jesus is risen?

Cal Metzger said...

VR: "Well, it seems clear to me that there can be pieces of evidence for things that may turn out not to be true."

There is information, and there are explanations for the information. The information doesn't serve the hypothesis; the hypothesis tries to best explain the information. If you stopped thinking about evidence as being "for" something I think you'd understand it better.

VR: "For example, my fingerprints on the murder weapon is evidence that I committed the murder even if the total evidence suggests that someone else did it."

Again, no. Your fingerprints on the murder weapon are evidence that your finger was the last to leave an impression on the murder weapon's trigger. Look at that evidence, AND ALL THE OTHER EVIDENCE, then explain it all. Explanations work for the evidence, not the other way around.

It truly boggles me that you can't grasp this fundamental and highly productive way of viewing evidence.

VR: "Finally, if one disciple says "I saw the risen Jesus," and a second one says "I did, too," doesn't that means the evidence can be, and was, checked, and therefore Jesus is risen?"

It's questions like the one directly above that incline me to think you will never understand evidence and basic critical thinking.

Cal Metzger said...

Entirely: "Cal has argued on Loftus's blog that Z here should include, "and I think that Y is true." That is, he will not admit the existence of evidence for anything that overall he believes to be false."

I don't think this is quite right. I am not talking about the "existence" of evidence, I am talking about the attribution (or use) of that evidence in an explanation.

Here's an easy example, using Victor's murder analogy: the murder weapon, with Victor's fingerprints on it, is discovered in a dumpster. Those are the facts. That is the evidence.

In this case, there are these two competing explanations: Victor murdered someone with that weapon, or, someone planted that weapon in an attempt to frame Victor for the murder.

Now imagine someone mails a letter, apparently written in Victor's handwriting, confessing to his intent to commit the murder.

Now imagine someone steps forward, stricken with guilt, and confesses that they had indeed been trying to frame Victor for murder, but now they confess and demonstrate how they planted the fingerprints, forged the letter, etc.

At this point, do you still think that the doctored murder weapon and the forged confession are evidence "for" Victor having committed the murder? Of course not -- they're evidence that supports the fact that someone tried to frame Victor for murder.

And that's the point. Explanations revise the understanding of evidence, including what is and what isn't evidence. It's not set in stone because any set of information can give rise to an explanation, and sometimes a new explanation introduces additional evidence and discovers that some evidence is now extraneous, but that's just a natural part of the give and take.

Legion of Logic said...

Cal,

In the case of evidence for God, how would you apply the process outlined in your latest post to that subject?

unkleE said...

I'm not a philosopher, but I think the definition "evidence is something that is examinable -- something that can be "checked out" in ways that are objective, reliable, and verifiable." raises many issues for me.

1. Does this definition distinguish between good evidence and weak evidence? What if two witnesses in a court disagree, so "verifiable" is problematic? Is that still evidence? Who decides what constitutes verification, or what is reliable? I think this definition might allow people to dismiss evidence easily if they don't like it - e.g. b y poisoning the well.

2. If a public opinion survey asks 10,000 people for their voting intentions, and the results show 70% will vote for party X, is this evidence? Each opinion is not "examinable, objective, reliable", it is taken on trust, subjective and liable to change. Nevertheless, statistically, the outcome is fairly assured. I'd say it was evidence but it doesn't seem to meet this definition.

3. Likewise if a couple is in a relationship, and one tells the other they love them, is this sufficient evidence that they really do love them? Can the other base a decision on making the relationship more permanent on that basis?

I'm inclined to think all of these cases are evidence that is somewhat less than examinable, objective, etc. That may, or may not, make the information less reliable evidence, we could argue about that, but I can't think that the information isn't evidence at all. I wonder what others think.

Joe Hinman said...


For the umpteenth time, evidence is something that is examinable -- something that can be "checked out" in ways that are objective, reliable, and verifiable.


buy the book! it's in there. Verifiable, empirical . the whole 9 yards every study peer reviewed published in secular academia. buy it....

The Trace of Godrational Warrant for Belief. by Joseph Hinman on amazon.

Joe Hinman said...

logic can be evidence, one can checkout logic.

entirelyuseless said...

"At this point, do you still think that the doctored murder weapon and the forged confession are evidence "for" Victor having committed the murder? Of course not -- they're evidence that supports the fact that someone tried to frame Victor for murder."

They are, from the beginning, and remain, evidence for both theories. I don't need to repeat our argument from Loftus's blog; anyone who wants can still read it there and see the absurdity of your account.

Cal Metzger said...

Legion: "In the case of evidence for God, how would you apply the process outlined in your latest post to that subject?"

It doesn't seem to me that there is any good evidence for any gods -- I think at best there is evidence, misattributed, to a (theistic) god.

Is lightning evidence of Zeus's anger, or electrical discharge in the atmosphere? The second explanation (electrical discharge) moves the evidence into its corner, so to speak, by providing a better (simpler, better scope, consistent with experience, allows for prediction, etc.)

Are the stories told about Muhammed evidence of Yawheh changing his mind about his message, naming a speaker on his behalf, and offering eternal life to those who believe in him, or is it better explained as a religious cult forming around magical stories, offering cohesion and meaning and purpose and the support of a community to those who joined?

Are the stories found in the NT evidence for the claims of Christianity (a theistic god, resurrection, magical healing, etc.), or are they evidence of one of many religious cults forming around stories that fulfill peoples' needs for meaning, purpose, and offering support and cohesion?

All of the world's successful religions offer inducements for gaining and keeping adherents -- from the positive (a sharing community, a sense of purpose, a code of conduct, etc.) to the negative (the loss of family and friends from shunning all the way to the real risk of death for heresy, apostasy, etc.). That various religions are more or less good at doing all this is unquestionable. But it's the magical stories that they tell -- the uncheckable stories that aren't consistent with reality -- that sets them apart from more mundane systems (like clans, or nationalism, which offer similar benefits and inducements).

The problem with religion isn't that it doesn't work -- clearly, it does. The only real problem with religions is that they tell stories about things that they don't really know to be true, and that these stories have soooo much better explanations than that the stories actually happened once in reality.

Cal Metzger said...

Unkle: "1. Does this definition distinguish between good evidence and weak evidence?"

Yes. Good evidence can be checked. Weak evidence can't be checked. It really is that simple.

Unkle: "What if two witnesses in a court disagree, so "verifiable" is problematic? Is that still evidence?"

Testimony (that can't be checked) is weak evidence.

Unkle: "Who decides what constitutes verification, or what is reliable? I think this definition might allow people to dismiss evidence easily if they don't like it - e.g. b y poisoning the well."

If something can be verified it can be checked again -- by you, or by someone else.

If something is repeatable, it is reliable.

I don't see how someone could "poison the well" over something so basic.

SteveK said...

"Is lightning evidence of Zeus's anger, or electrical discharge in the atmosphere?"

Depends on the type of cause you're looking to explain. By mere observation we can see that the proximate cause is not Zeus, God or any other being. From that perspective lightening is not evidence for either. Looking at the originating cause the answer can't be another proximate causes with the same contingent nature so Zeus is ruled out, but not God. From that perspective lightening is evidence for God.

Joe Hinman said...

the lightning analogy was meant to discredit abductive reason but abductive reasoning is legitimate and widely accepted ben in atheistic philosophy circles. The best explanation. Charles Sanders Peirce made an abductikve argument for God.

Cal Metzger said...

So, lightening is evidence for Yahweh?

You guys must be so proud.

SteveK said...

Yup

B. Prokop said...

Gotta agree with SteveK here. Lightning is indeed evidence for "Yahweh" [God]. As is anything whatsoever that exists, as well as each and every physical phenomenon, be it electromagnetism, gravity, the strong and weak forces, or atomic decay.. in short, everything. It's all evidence.

Jezu ufam tobie!

SteveK said...

As I like to say to people like Cal....

I just believe in one more God than you do. When you understand why I don't dismiss my God, you will understand why I do dismiss all the others.

Cal Metzger said...

SteveK: "I just believe in one more God than you do. When you understand why I don't dismiss my God, you will understand why I do dismiss all the others."

I do understand why you believe in your god. Because your god was part of the culture in which you grew up.

And you dismiss all the others because you didn't grow up with those gods.

Cal Metzger said...

So, to sum up, Victor says that whenever he asks why his method for considering evidenced is flawed, no one has ever been able to explain how evidence is supposed to work.

I point out that I've explained how evidence should work many, many times here, and I go on to explicate again.

Then I hear back things like this:
- When something can be known to be a forgery, it remains evidence that it is the real thing, and not a forgery.
- Lightning is evidence for Yahweh.
- Everything is evidence for Yahweh.

What are the odds that in the next 2 weeks to 3 months, Victor will post that no one can explain how evidence is supposed to work, and that the usual crew will enlighten with their takes, all around the theme that evidence is what their god belief is all about. All evidence to the contrary.



unkleE said...

Hi Cal, thanks for your comments on my questions. I'd like to explore them a little more if I may, because I think they reveal something about your original statement.

"Good evidence can be checked. Weak evidence can't be checked. It really is that simple."

I have two problems with this. (1) It is very binary, whereas the real world isn't. There is a gradation between good and weak evidence, and a gradation of how checkable something is. It isn't as simple as you say. (2) But more importantly, "weak evidence" is, by definition, evidence, yet you say here it can't be checked. Yet your original statement was "evidence is ... something that can be "checked out"". These two statements disagree. I agree with your second statement, which is partly why I questioned your first statement.

"Testimony (that can't be checked) is weak evidence."

So I agree with you here. But that means that things that can't be checked may still be evidence, though we would all agree that things that can be checked are better evidence.

"If something is repeatable, it is reliable. "

Repeatability is one aspect of reliability, but would you agree that it isn't the only aspect? For example, if Stephen Hawking told me something about cosmology that he thought was true but it couldn't be repeated, I would still think it was probably reliable information, certainly more reliable than if my plumber friend told me. So reliability is an assessment, and you might assess a source as more or less reliable than I might.

"I don't see how someone could "poison the well" over something so basic."

I see it all the time. Someone offers what they believe is evidence and instead of discussing the strength or otherwise of the evidence, their opponent argues it isn't evidence at all on some grounds like your original statement. Because reliability is an assessment, it is in some senses subjective. So opponents often denigrate the person offering the evidence to justify their low assessment of reliability.

So my point is, it seems from your replies that the matter isn't as simple as your first definition suggested. There are complexities, and a wide range of apparent facts may be evidence, albeit of varying quality. Would you agree?

planks length said...

"I do understand why you believe in your [G]od. Because your [G]od was part of the culture in which you grew up."

Irrelevant. You grew up in the same culture, and do not believe in Him. Therefore, there is no cause and effect relationship. (And here I thought "repeatability" was supposed to be an essential element of evidence. I guess that only counts when you want something to repeat.)

Cal Metzger said...

Unkle: "I have two problems with this. (1) It is very binary, whereas the real world isn't."

The real world can be very binary. Your being dead is a very binary event. Same with pregnant. Etc.

Unkle: "There is a gradation between good and weak evidence, and a gradation of how checkable something is. It isn't as simple as you say."

Some things can be checked, and some things can't. That is both simple, and correct. The laws of physics can be checked. A video or photo or other recording can be checked. An archaeological structure can be checked. Any extant physical thing can be checked. This is simple, and true.

Unkle: "(2) But more importantly, "weak evidence" is, by definition, evidence, yet you say here it can't be checked."

You introduced the term "weak evidence" here, and you say it is evidence. I agree that what you call "weak evidence" is something, but calling something like hearsay "evidence" and abandoning all the caveats that make it "weak" is a kind of sleight of hand. So I resist it, and point out that what we should mean by evidence is good evidence, and good evidence can be checked.

Unkle: "Yet your original statement was "evidence is ... something that can be "checked out"". These two statements disagree."

Seeing as how the second term "weak evidence" is yours, and you are disagreeing with my characterization of evidence, then you are just pointing out that your statement disagrees with mine. I don't see what I need to clarify for you in my statements.

Unkle: "Repeatability is one aspect of reliability, but would you agree that it isn't the only aspect? For example, if Stephen Hawking told me something about cosmology that he thought was true but it couldn't be repeated, I would still think it was probably reliable information, certainly more reliable than if my plumber friend told me."

By reliable I mean repeatable. If Hawking told you what he thought I would consider it interesting, but if the thing he was talking about wasn't reliable (repeatable), then his talking about it wouldn't make it reliable (repeatable). It would make it something that Hawking thought about, but that that thing wasn't a reliable (repeatable) event. I don't think there's any other way I can explain it for you -- Hawking's saying something about something doesn't make that something reliable. Our ability to check out that thing that Hawking talked about, to observe again what he had observed, that is what would make the thing reliable.

Unkle: "So reliability is an assessment, and you might assess a source as more or less reliable than I might."

An event is reliable, or it is not. We could disagree, but the event should be able to arbitrate our difference.

Unkle: "I see it all the time. Someone offers what they believe is evidence and instead of discussing the strength or otherwise of the evidence, their opponent argues it isn't evidence at all on some grounds like your original statement."

I'm starting to think I know the reason you hear this all the time.

unkleE said...

Hi Cal, thanks again for your elaboration. I must say I'm a little concerned about your last comment. I don't really know what you mean, but it seems like you're having a go at me. I'm sorry if I have offended you or caused you to think badly of me. If you would prefer I stopped discussing this, please say so.

"The real world can be very binary."

Of course I agree with this, but we were talking about evidence. Do you mean you think evidence is binary then - either good or weak, but nothing in between? That seems to be what you are saying. But we all know that things can be known to certain degrees of probability, which is far from binary. So I'm unsure what you mean.

"Some things can be checked, and some things can't."

Does this mean you think that they are the only possibilities? Again, isn't it possible that some things can be checked well (e.g. the measurement of a water quality indicator) while other things can only be checked approximately (e.g. the identification and dating of pottery shards by archaeologists)? So evidence isn't always binary asa far as I can see.

"You introduced the term "weak evidence" here, and you say it is evidence. I agree that what you call "weak evidence" is something, but calling something like hearsay "evidence" and abandoning all the caveats that make it "weak" is a kind of sleight of hand. So I resist it, and point out that what we should mean by evidence is good evidence, and good evidence can be checked."

I wasn't attempting any "sleight of hand", I was just pointing out that while I introduced the term "weak evidence", you also used the term. So unless you think you are having second thoughts about your usage, it illustrates again that there is some gradation of evidence. I'm trying to understand if you really think only perfectly reliable and repeatable information can be classed as evidence, or whether you accept (say) 95% confidence limits, whether you would accept (say) 75% confidence limits etc - i.e. where you draw the line. That still isn't clear to me.

"Hawking's saying something about something doesn't make that something reliable. "

Does this mean you don't accept expert opinion as evidence, as a court does? Take my example of ancient pottery shards - if they cannot be dated by some form of radiometric dating, archaeologists rely on their location in the site and their expert knowledge of other pottery finds to make an informed estimation of dating. There will be some margin for error, but the period they come from will be assessed. Do you think that is not evidence-based?

Or take another example. I used to work as an environmental manager of rivers and catchments in NSW, Australia. We have a large land area and a small population, so we don't have the resources to collect all the scientific data we would like - less indicators that we'd like, measured less often and over a shorter period of time than we'd like. Yet management decisions need to be made, or many riverine ecosystems would be destroyed before we ever collected enough data to make a reliable choice. So we would augment our inadequate data with a review by an "expert panel" made up of scientists from different environmental disciplines, who would give the best judgment on questions which the data couldn't fully resolve. So I think we were using an evidence-based approach at the only practical level possible. Would you say the inadequate data we collected and the expert advice was evidence, albeit not as much as we would like, or would you say it wasn't? Would you have made management on that basis, or would you have waited?

I am interested to better understand what you think. Thanks.

Cal Metzger said...

Unkle: "Do you mean you think evidence is binary then - either good or weak, but nothing in between?"

I am saying that the term "evidence" should be reserved for what you are distinguishing as "good evidence," and that what you are calling "weak evidence" we should call what it is -- testimony, hearsay, an educated consensus, a story, etc. When someone uses the term "evidence" to mean both the effects of gravity AND an archaelogical site AND an extant document AND a story told by anonymous sources, then we have a clear problem of equivocation. I am pointing that out.

Me: "Some things can be checked, and some things can't."
Unkle: "Does this mean you think that they are the only possibilities? Again, isn't it possible that some things can be checked well (e.g. the measurement of a water quality indicator) while other things can only be checked approximately (e.g. the identification and dating of pottery shards by archaeologists)? So evidence isn't always binary asa far as I can see."

It seems that you are confusing checkability with precision, accuracy, analytical method, margin of error, etc. A shard of pottery can be checked. That is a binary classification. A story told by an anonymous source cannot be checked. That is binary. What we should conclude about these things is subject to our judgments, yes, but that is separate from the fact that some things can be checked, and other cannot. So, no, it's not true that the checkability of evidence isn't binary -- for most practical purposes, it is.

Unkle: " I'm trying to understand if you really think only perfectly reliable and repeatable information can be classed as evidence, or whether you accept (say) 95% confidence limits, whether you would accept (say) 75% confidence limits etc - i.e. where you draw the line. That still isn't clear to me."

Yes, I saying that only those things that are objective, reliable, and verifiable (that can be checked) should be classified as evidence. Do we regularly rely on other, less rigorous methods to make everyday determinations? Of course we do. But just because we make determinations (heuristic judgments) on stuff that isn't reliable, verifiable, and objective (that can't be checked) doesn't mean that we should call those things "evidence."

I am proposing disambiguation of the term "evidence." Maybe that's what isn't clear.

Unkle: "Does this mean you don't accept expert opinion as evidence, as a court does?"

I think the legal definition for evidence is something separate from what we are talking about. If the expert opinion is about something that is checkable, then I think we're talking about evidence. If the expert opinion is about something that isn't checkable, then I wouldn't use the term "evidence." But courts call testimony "evidence," and I a) think that testimony that can't be checked isn't evidence, and b) will point out that testimony is famously unreliable (and that calling evidence is misleading).

Unkle: "Or take another example.... would you have waited?

Data from riverbeds should be checkable, so I would consider riverbeds data evidence. Not having enough data to make a good determination is something different, but that doesn't change the fact that there is evidence upon which a determination is made.

SteveK said...

"Do we regularly rely on other, less rigorous methods to make everyday determinations? Of course we do. But just because we make determinations (heuristic judgments) on stuff that isn't reliable, verifiable, and objective (that can't be checked) doesn't mean that we should call those things "evidence.""

If evidence (as you have defined it here) isn't needed for much of your everyday living and everyday knowledge why do you spend so much time arguing about the need for evidence?

Cal Metzger said...

SteveK: "If evidence (as you have defined it here) isn't needed for much of your everyday living and everyday knowledge..."

Not really what I'm saying.

We enjoy and rely on technology, for instance, because we have made a vast, vast number of decisions based on evidence. And we have organized the use of these technologies in such as way that we don't normally need to made judgments about them, because a) they work, and b) they can be checked on. We live in a market society with constant information and feedback, and these mechanisms all surround us in a cloud that does a pretty good job, more or less, of identifying those things that are based on evidence. Things based on evidence tend to work (or they're not adopted), and they are checkable.

People make an unfortunate number of detrimental decisions, though, based on claims that aren't really based on evidence -- and things that aren't really based on evidence often don't work, and there's no way to check on those claims beforehand to find out if they're going to work or not.

Mostly, though, I don't like equivocation -- equivocation is a kind of dishonesty. And I just can't help myself from being compelled to expose it.

unkleE said...

Hi Cal,

Thanks again for your explanations. I think it is probably time for me to sum up and close. I see this statement of yours as key to understanding your view: "I am saying that the term "evidence" should be reserved for what you are distinguishing as "good evidence," and that what you are calling "weak evidence" we should call what it is -- testimony, hearsay, an educated consensus, a story, etc."

I have no problem with distinguishing evidence from hearsay. The difference between us seems to be that you see those things as qualitatively different, and your answers indicate you think everything is either one or the other.

I can't see that myself. It seems clear to me that there is a continuum between good evidence and poor evidence or hearsay, and there are many things (probably most things) that come somewhere in the middle. You seem to want to avoid that. I think yours is a very unusual usage, but at least I can understand it.

Thanks.

Cal Metzger said...

Unkle: "I have no problem with distinguishing evidence from hearsay. The difference between us seems to be that you see those things as qualitatively different..."

The reason you distinguish between evidence (what can be checked) from hearsay is because they ARE qualitatively different.

Unkle: "...and your answers indicate you think everything is either one or the other."

Well, no. That's why I wrote, among other things, "If the expert opinion is about something that is checkable, then I think we're talking about evidence."

Unkle: "It seems clear to me that there is a continuum between good evidence and poor evidence or hearsay, and there are many things (probably most things) that come somewhere in the middle. You seem to want to avoid that."

And again, no. That's why I wrote, "Do we regularly rely on other, less rigorous methods to make everyday determinations? Of course we do. But just because we make determinations (heuristic judgments) on stuff that isn't reliable, verifiable, and objective (that can't be checked) doesn't mean that we should call those things "evidence." "

Unkle: "I think yours is a very unusual usage..."

My "unusual usage" is really just basic science.

Unkle: "..., but at least I can understand it."

You summary of my position seems odd, so I'm not so sure I've made myself clear to you. But whatever. Cheers.