Top 5 Skeptical Fallacies

[Giordano]

Dinwar, I've tried to be clear, but I think I'm failing

In your specific line of work, in this specific context, it is sufficient to deduce a lack of existence based on a lack of evidence.

Outside of specific contexts, however, it is NOT sufficient. It is not universally true. You cannot say "lack of evidence is evidence of lack" as a generality.

We lack evidence to support the hypothesis of dark energy. That does not imply that it does not exist. Until recently, we lacked evidence for the Higgs Boson - that did NOT mean that we had evidence that it didn't exist.

Outside of your field's use, lack of evidence cannot be used in the way you're using. It makes sense to deduce a lack of existence in your field. It does not make sense to do so in other contexts. Logic is universal, it is not context-dependent. Deductive reasoning is not universal, and is context dependent.

This thread is about logical fallacies. In order to discuss logical fallacies, we need to begin with formal logic.

If I may break in: there are many contexts in which lack of evidence is evidence of lack. These are the contexts in which a piece of evidence should be observable if something existed, yet that piece of evidence is not observed. Thus the car example (if there was a car in my garage I should be able to see it, and I don't, so there is no car in my garage) and the opposing dark matter example (if there was dark matter, we don't know exactly what we would expect to see, so not seeing something doesn't necessarily mean that there is no dark matter). So they are both consistent. By the way- dark matter, as it typically defined, is used to explain a real observation (the way galaxies behave), so there is evidence for "dark matter" even though exactly how to define this entity is unclear. And people use this logic all the time (If my spouse was home I would see, hear, and feel them. I do not. Therefore they are not home).

Of course one must be careful that the predicted observation is indeed a correct interference (if I was blind then my prediction that I should see my spouse if they were home would be an incorrect inference). Very similarly, one must be careful that one's lack of observation is sufficient to apply to the logical inference: if I only checked the living room and kitchen of my house, then my observation is too incomplete to allow me to say that my spouse is not home.

 

[Donn]

… we're the only scientific field I know of where explosives have been banned because paramilitary tactics and scientific exploration don't go together....

Ah, din and war are now making sense.

 

[Dinwar]

You seem very argumentative, where I'm not really trying to argue with you.

You came in saying "You are wrong". OF COURSE I'm going to defend myself. The fact that I think you are wrong should be self-evident. And while your tone may be more moderate than mine, the implications of your arguments are far worse.

I disagree with you stating it as a generality. It is not universally true.

Allow me to clarify: I differentiate between evidence as such, good evidence, and proof.

Evidence merely needs to support a conclusion.

Good evidence needs to support ONE conclusion (evidence supporting multiple conclusions is evidence, but not good evidence).

Proof needs to disallow any other conclusion.

Given those definitions, a lack of evidence IS EVIDENCE OF A LACK--in as much as one explanation for the lack of evidence is that the thing in question is nonexistent. Alternative explanations may be possible, so we can debate whether it's good evidence or not.

Your job, since you disagree with me, is to show that my definitions are wrong, or that my logic contradicts the definitions or itself.

Thus far you have failed to do so. You have merely repeated that I am wrong, and appealed to unnamed authorities supporting this.

Hypotheses and mathematical models do NOT constitute evidence.

This demonstrates your lack of understanding of the scientific process. The question you are refusing to ask is "What are those hypotheses and mathematical models based on?" They didn't perform a craniorectal extraction to produce them; they are based on data. Those data support the hypotheses--some better than others, but never the less they support it. THAT is the data I was referring to.

The way you present it, hypotheses are these mystical disembodied entities that scientists merely produce, and THEN look for evidence to support. Nothing could be further from the truth. The reality is that hypotheses are based on deep understanding of the available data, and are typically a consequence thereof. Mathematical models are the same, with the additional step of ground-truthing (meaning no model excapes into the literature without being tested a few times, and each test is data supporting it).

You are performing a very shallow analysis of these issues, something that does not bode well for someone making an argument from formal logic.

Otherwise you're in the position of saying we had evidence for an earth-centered solar system, it just wasn't "firm" proof.

I'm perfectly happy to accept this conclusion. There is evidence for a geocentric model of the universe. It's not good evidence, as it also is evidence of the standard model now in use, a heliocentric model, and a few others. And it contradicts other evidence, further degrading its value. However, one can easily find data supporting the conclusion that the Earth is the center of the universe; therefore there is in fact evidence for it. I'm not someone who consideres my intellectual ancestors incompetant, drooling morons; their conclusions were often wrong, but NOT unsupported, and understanding how they were wrong is critical to understanding how WE might be wrong.

Again, where you err is in assuming "evidence" and "proof" are the same. This is patently untrue. There's evidence for all kinds of nonsense; systematic and critical evaluation of the evidence is necessary to draw valid conclusions.

Of course one must be careful that the predicted observation is indeed a correct interference (if I was blind then my prediction that I should see my spouse if they were home would be an incorrect inference). Very similarly, one must be careful that one's lack of observation is sufficient to apply to the logical inference: if I only checked the living room and kitchen of my house, then my observation is too incomplete to allow me to say that my spouse is not home.

Well said, and certainly worth bearing in mind. If we'd only looked in one small portion of North America, we could not use the lack of bigfoot remains to draw any conclusions; it is the fact that there have been repeated, systematic explorations of the area looking specifically for such evidence (and believe me, you have no idea how many there have been--bio, cultural, and paleo compliance alone provides hundreds of such surveys a year) that allows us to do so.

 

[jt512]

You cannot say "lack of evidence is evidence of lack" as a generality.

Yes you can, if you state it rigorously: If hypothesis H1 predicts that evidence E should have been observed, and if the complementary hypothesis, H0, predicts that the absence of evidence E should have been observed, then observing the absence of evidence E is evidence against hypothesis H1 (and in favor of H0).

Until recently, we lacked evidence for the Higgs Boson - that did NOT mean that we had evidence that it didn't exist.

Let's assume that that was true at the time. Then it was because at that time we lacked the ability to observe such evidence. Therefore, the Higgs hypothesis did not predict that there was evidence that should have been observed at that time. In other words, there is a difference between a lack of evidence that should have been observed and lack of evidence that no one has looked for, or been able to look for.

 

[Emily's Cat]

You came in saying "You are wrong". OF COURSE I'm going to defend myself. The fact that I think you are wrong should be self-evident. And while your tone may be more moderate than mine, the implications of your arguments are far worse.

Actually, I didn't. I came in saying:

Logically, this isn't true. Lack of evidence is NOT evidence of lack. This is an established proposition for argumentation.

Lack of expected evidence is sufficient reason to reject a claim.

In fact, at no point in this discussion have I said you are wrong. You are the only person to have made such a blanket claim. What I have said, and you seem to be unable to grasp, is:

In some situations, it is reasonable to conclude a lack of existence due to a lack of evidence, but it is not a general axiom, and presenting it as if it is a general axiom is supporting errant logic on the whole. The worst thing I've asked of you is that you be more specific in your application of that particular yardstick.

Allow me to clarify: I differentiate between evidence as such, good evidence, and proof.

Evidence merely needs to support a conclusion.

Good evidence needs to support ONE conclusion (evidence supporting multiple conclusions is evidence, but not good evidence).

Proof needs to disallow any other conclusion.

Given those definitions, a lack of evidence IS EVIDENCE OF A LACK--in as much as one explanation for the lack of evidence is that the thing in question is nonexistent. Alternative explanations may be possible, so we can debate whether it's good evidence or not.

Your job, since you disagree with me, is to show that my definitions are wrong, or that my logic contradicts the definitions or itself.

Thus far you have failed to do so. You have merely repeated that I am wrong, and appealed to unnamed authorities supporting this.

I have done neither thing.

This demonstrates your lack of understanding of the scientific process. The question you are refusing to ask is "What are those hypotheses and mathematical models based on?" They didn't perform a craniorectal extraction to produce them; they are based on data. Those data support the hypotheses--some better than others, but never the less they support it. THAT is the data I was referring to.

The way you present it, hypotheses are these mystical disembodied entities that scientists merely produce, and THEN look for evidence to support. Nothing could be further from the truth. The reality is that hypotheses are based on deep understanding of the available data, and are typically a consequence thereof. Mathematical models are the same, with the additional step of ground-truthing (meaning no model excapes into the literature without being tested a few times, and each test is data supporting it).

Notice that you are speaking within a specific context of scientific research? That is a boundary constraint on the occasions where absence of evidence implies evidence of absence.

You are performing a very shallow analysis of these issues, something that does not bode well for someone making an argument from formal logic.

I'm perfectly happy to accept this conclusion. There is evidence for a geocentric model of the universe. It's not good evidence, as it also is evidence of the standard model now in use, a heliocentric model, and a few others. And it contradicts other evidence, further degrading its value. However, one can easily find data supporting the conclusion that the Earth is the center of the universe; therefore there is in fact evidence for it. I'm not someone who consideres my intellectual ancestors incompetant, drooling morons; their conclusions were often wrong, but NOT unsupported, and understanding how they were wrong is critical to understanding how WE might be wrong.

A mathematical model is an attempt to explain physical phenomena. It does not constitute evidence of a cause until such point as that model has validated predictions of the phenomenon in question. A mathematical model by itself is not evidence.

The geocentric model of the solar system failed because it did not validate predictions. It came close, but with each subsequent set of observations, errors were observed, and the model was further tinkered with to try to explain those observations. It was never a stable model.

The heliocentric model is viewed as evidence because it makes predictions that are validated by observation. It has been a stable model without the need for subsequent tinkering for what? A couple hundred years now?

Just because maths can be invented to describe or explain a phenomenon does not make that pile of formulas "evidence". If it were, then any set of explanatory wiffling would be acceptable as evidence. Any hypothesis that explains why we find no physical evidence of bigfoot would then have to be accepted as evidence of bigfoot's existence. That's clearly absurd.

Again, where you err is in assuming "evidence" and "proof" are the same. This is patently untrue. There's evidence for all kinds of nonsense; systematic and critical evaluation of the evidence is necessary to draw valid conclusions.

There are explanatory hypotheses for all kinds of nonsense. There is not evidence for them all. I can toss together an unfalsifiable collection of hogwash for why my sister's dog ate her homework. That doesn't make it evidence.

 

[Emily's Cat]

Yes you can, if you state it rigorously: If hypothesis H1 predicts that evidence E should have been observed, and if the complementary hypothesis, H0, predicts that the absence of evidence E should have been observed, then observing the absence of evidence E is evidence against hypothesis H1 (and in favor of H0).

That's never what H0 means. You're assuming a perfectly bifurcated solution set... which would need evidence to support your assumption that only two possible outcomes are possible.

H0 is always "we can't tell". Your specific H1 then is "If we observe E then we can reject the null - we will be able to tell for sure".

H0 is NEVER a falsifiable hypothesis. That's why it's a null hypothesis. You can reject the null hypothesis if you H1 pans out, but you can never accept the null. That would require you to have exhausted every possible Hn that could possibly be imagined ever in the entirety of time .

In the context of bigfeet, H0 is "bigfoot is indistinguishable from imagination". All of your set of Hns then are cases of "Evidence En exists to show that bigfoot is not imaginary". We have a repeated set of Hns that fail to reject the null. It is reasonable to conclude that bigfoot is indistinguishable from imagination, and assume that such a creature does not exist. But you cannot conclude that bigfoot does not exist and simply shut the book on it - because you cannot prove nonexistence of a thing.

Let's assume that that was true at the time. Then it was because at that time we lacked the ability to observe such evidence. Therefore, the Higgs hypothesis did not predict that there was evidence that should have been observed at that time. In other words, there is a difference between a lack of evidence that should have been observed and lack of evidence that no one has looked for, or been able to look for.

We tried many different approaches to find evidence of the Higgs. We looked quite hard, we simply didn't have any luck with those approaches. That did NOT lead us to conclude that the Higgs did not exist. All it led to is that we could not tell whether it existed or not.

 

[John Nowak]

The heliocentric model is viewed as evidence because it makes predictions that are validated by observation. It has been a stable model without the need for subsequent tinkering for what? A couple hundred years now?

Sixty, maybe? Einstein changed the way gravity worked, which explained some issues with Mercury's orbit.

 

[Emily's Cat]

Sixty, maybe? Einstein changed the way gravity worked, which explained some issues with Mercury's orbit.

More like 80, with that. Einstien's stuff was around WWII, wasn't it? That puts it in the 30s, and we're now in the teens.

 

[Pixel42]

More like 80, with that. Einstien's stuff was around WWII, wasn't it? That puts it in the 30s, and we're now in the teens.

Nope. Special relativity 1905, General 1915. So more like 100.

 

[John Nowak]

Nope. Special relativity 1905, General 1915. So more like 100.

Wikipedia agrees with you -- apparently General Relativity was used to account for Mercury's orbit in 1915. 100 years, then, although that will likely change.

 

[Emily's Cat]

Glad we got that sorted!

 

[John Nowak]

Glad we got that sorted!

I think the point, though, is that both geo- and heliocentric models were tweaked over time as observational techniques and records improved. Such tweaking is likely to continue in the future - I don't believe anyone's accounting for dark matter in solar-system sized models yet, just because the model doesn't call for adjustments which are detectable at this time. Both theories evolved over their lifetimes.

 

[Dinwar]

Actually, I didn't. I came in saying:

This reads as "I didn't say you were wrong, I merely said you weren't right."

I have done neither thing.

Fine. You ALSO have not addressed my arguments.

Notice that you are speaking within a specific context of scientific research? That is a boundary constraint on the occasions where absence of evidence implies evidence of absence.

Notice how you ignored the underlying principle? THAT is what I'm complaining about. Being scientific is not a magical incantation that makes lack of evidence transmorgify into evidence for abscense; there's a REASON for it. That reason is not confined to the scientific process.

The geocentric model of the solar system failed because it did not validate predictions.

And this addresses the fact that the geocentric model had evidence supporting it how, exactly?

We can dismiss the paragraph before, and everything that came after, this statement because it all is based on the false premise that I was saying the evidence consisted of a mathematical model. I was not. The evidence conists of how the stars, planets, and other celestial bodies moved through the sky. The ancients observed that, and observed that they felt no motion, and concluded the heavens revolve around the Earth. They were wrong, and increasing amounts of data forced them to revise those views--which is where epicycles and the like came from--but none of that invalidates the earliest observations. THOSE OBSERVATIONS are the evidence. Incomplete? Sure. But it takes a lot of gaul to fault someone for an incomplete dataset when they didn't have access to a more complete one.

You have a rather bad habit of assuming I'm talking about X, and arguing against X, when in fact I've said nothing of the sort and was actuallying thinking about Y. I can't WAIT to see what you think I had in mind regarding my statement about mathematical models never being evidence. Five'll get you ten you're pretty far off base.

There are explanatory hypotheses for all kinds of nonsense. There is not evidence for them all.

None? Doubt that. No STRONG evidence, sure. No PROOF, certainly. No evidence AT ALL? NO data supporting the conclusion? That's a pretty bold statement, and one that relies upon ignoring what the other side says.

I can toss together an unfalsifiable collection of hogwash for why my sister's dog ate her homework. That doesn't make it evidence.

Possibly, possibly not. "My sister's dog ate my homework" is a conclusion, and therefore not evidence at all.

Secondly, the evidence for geocentrism isn't unfalsifiable. We know that because it was falsified. Or, more accurately, better understanding led to revised interpretations. We don't feel motion because we share the same inertial frame of reference, like tossing a ball up and down on a moving train. That sort of thing. There's a reason we gave up the notion, and by accepting that our ancestors weren't morons I by no means am attempting to refute the modern views (I'm curious as to how a geologist COULD honestly refute at least the helocentric model; too much relies upon it).

All I'm saying is that I'm willing to accept that people have reasons for what they believe, and often they are real reasons. The error is generally, in my experience, not that a false belief has no evidence--it's that the false belief relies on poor evidence, incomplete datasets, or erronious interpretations. Your basic assumptions are the underpinnings of intellectual sloth.

H0 is NEVER a falsifiable hypothesis.

False. See Strong Inferrence. If you're going to take this tone, you should at least have a compete dataset yourself.

 

[Dinwar]

I think the point, though, is that both geo- and heliocentric models were tweaked over time as observational techniques and records improved.

Not my original point, no. My original point was merely that the ancients had data supporting their conclusions--and therefore had evidence. This argument is entirely independent of any discussion of the quality of the conclusions, or the quality of the evidence (though I've agreed it was not good evidence, as it supported multiple hypotheses or was later disproven).

 

[John Nowak]

Not my original point, no. My original point was merely that the ancients had data supporting their conclusions--and therefore had evidence. This argument is entirely independent of any discussion of the quality of the conclusions, or the quality of the evidence (though I've agreed it was not good evidence, as it supported multiple hypotheses or was later disproven).

Of course, it depends which theories you're talking about. The Greeks got the size of the Earth better than Columbus did, but some of the natural history stuff is kind of weird.

 

[Dinwar]

Of course, it depends which theories you're talking about. The Greeks got the size of the Earth better than Columbus did, but some of the natural history stuff is kind of weird.

Agreed. Some conclusions really did come out of thin air (see Aristotle's work on physics, and the assumptions therein!). But many--I would say most--have SOME basis in reality. The difference between me and a Geocentrist isn't that I rely on data and they do not; the difference is which data we both use.

 

[Emily's Cat]

This reads as "I didn't say you were wrong, I merely said you weren't right."

More to the point, I didn't say you were wrong; I said that what you said isn't ALWAYS right. Holy cow, man. Is it seriously that hard for you to back down a teensy bit and say "Well, absence of evidence is sufficient to assume evidence of lack in many case, but may not always be universally true"? Because that's is the only thing I've taken issue with. You're presenting it as if it is universally true all the time, because it is true in a particular context.

Notice how you ignored the underlying principle? THAT is what I'm complaining about. Being scientific is not a magical incantation that makes lack of evidence transmorgify into evidence for abscense; there's a REASON for it. That reason is not confined to the scientific process.

And that reason is ALSO not universally true all the time!

None? Doubt that. No STRONG evidence, sure. No PROOF, certainly. No evidence AT ALL? NO data supporting the conclusion? That's a pretty bold statement, and one that relies upon ignoring what the other side says.

Holy cow. LEARN TO READ. Try it again:

There are explanatory hypotheses for all kinds of nonsense. There is not evidence for them all.

Show me where I said or even implied "none". Show me where anything that you're saying here even remotely follows from my statement.

Secondly, the evidence for geocentrism isn't unfalsifiable.

Jesus. Evidence is evidence - it is facts. The hypothesis for geocentrism was falsifiable, and I certainly never claimed it wasn't. I mean, I guess tefchnically if you're dealing with fraud, the evidence could be falsifiable, but that makes this an entirely different discussion altogether!

False. See Strong Inferrence. If you're going to take this tone, you should at least have a compete dataset yourself.

The null hypothesis is the hypothesis that there is no discernible difference between the thing being measured and the starting position. It is literally the hypothesis that the difference is not statistically significant. This does NOT mean that they ARE the same - it means only that the test in question cannot conclude that they're different. That's what the null hypothesis is! That is it's entirety!

There is NEVER enough evidence to conclude that they are the same. You can only fail to reject the null; you cannot accept the null. That's how inferential statistics works. That's how hypothesis testing works.

All I'm saying is that I'm willing to accept that people have reasons for what they believe, and often they are real reasons. The error is generally, in my experience, not that a false belief has no evidence--it's that the false belief relies on poor evidence, incomplete datasets, or erronious interpretations. Your basic assumptions are the underpinnings of intellectual sloth.

So let me get this straight... You simultaneously want to argue that 1) Absence of evidence is Evidence of Absence and 2) That false beliefs don't rely on absence of evidence, just on poor evidence.

Wouldn't that invalidate your first claim? You want to simultaneoulsy hold that 1) Bigfoot doesn't exist because there is no evidence for him and 2) Bigfoot Believers believe in bigfoot because of bad evidence?

Wouldn't that imply that there IS evidence for bigfoot (albeit poor evidence), and thus you cannot conclude that he doesn't exist?


++++++++++++++++++++++++++

Look Dinwar - this is the most absurd argument on the face of the planet. Neither you nor I think there is sufficient evidence to support a bigfoot hypothesis. We both think it's a load of hooey.

The ONLY place we actually seem to differ in on a nuance:
You seem to be saying "No evidence that meets my criteria means that big foot does not exist, and means ONLY that".
I, on the other hand, am saying "Insufficient credible evidence for the existence of bigfoot leads to the inference that there is no reason to conclude that big foot exists"

My sole disagreement with you is in the presentation of "Absence of Evidence -> Evidence of Absence" as a universally true statement. I've tried again and again to make it clear that I understand the application in this context, and that I don't disagree with it being treated as a litmus test in this context. I only disagree with it being presented as an axiomatically true statement.

Why are we arguing?

 

[Dinwar]

More to the point, I didn't say you were wrong; I said that what you said isn't ALWAYS right.

Which is inherent in my repeated statement of the fact that I'm basing this off a logical principle.

Is it seriously that hard for you to back down a teensy bit

You are continuously mis-stating my argument, presenting made-up nonsense as my argument, and refusing to acknowledge arguments I have made. GIVE ME A REASON to back down a teensy bit.

And that reason is ALSO not universally true all the time!

Do you understand what the underlying principle is? The fact that you keep attempting to put ad-hoc limitations on the use of lack of evidence is a pretty good indication that you do not. Here's a hint: the principle was stated simply and clearly in this thread.

Evidence is evidence - it is facts.

If you'd continued reading, you'd see that I addressed that issue (for someone who capitalized "LEARN TO READ", I find this error quite obnoxious on your part). Facts can be interpreted numerous different ways--that's what gives rise to poor evidence. It is a FACT that we do not feel the Earth move. What causes that has been disputed. It is a FACT that we see the various celestial bodies move across the sky; the explanation of this has been disputed.

The null hypothesis is the hypothesis that there is no discernible difference between the thing being measured and the starting position.

Not always.

I assume, by your response, that you did not google the concept "Strong Inferrence"?

For someone demanding I learn to read, you've done a poor job of it yourself thus far.

You simultaneously want to argue that 1) Absence of evidence is Evidence of Absence and 2) That false beliefs don't rely on absence of evidence, just on poor evidence.

I want to argue the following:

Pretty much, yeah, though you've stated both in the worst possible light. Absence of necessary evidence is evidence of absence; that's what "necessary" means. And most false beliefs have very bad evidence supporting them, which is why we must look for necessary evidence. To use bigfoot as an example: The evidence supporting it is personal sightings, ie, eye witness accounts. It's data, but it's just about the worst type. The necessary evidence--evidence that the hypothesis demands be present--are remains, scatt, and the like; the absence of those is evidence for the absence of the organism.

The fact that you wish to present my arguments in the worst possible light is where your views that they contradict one another come from. It has nothing to do with what I'm actually proposing.

The ONLY place we actually seem to differ in on a nuance

That's right. However, it's a vital nuance. Your view is not practical, is not applied by literally ANYONE outside the most ivory-tower philosophers in the most formal settings, contradicts common usage, and encourages the sort of intellectual slovenliness that characterizes the worst aspects of this forum.

My sole disagreement with you is in the presentation of "Absence of Evidence -> Evidence of Absence" as a universally true statement.

No, it's not. It's really not. Our disagreements are over how, fundamentally, to apply logic--you taking, as far as I can tell, a very rule-based approach, while I focus on the principles guiding those rules. Note that I keep referencing a principle for why lack of evidence is evidence of lack, while you keep attempting to establish ad hoc boundaries to it.

Why are we arguing?

Because mistakes like the ones you are making are dangerous. They infect one's thinking in other areas. I see no reason to give you a pass merely because we agree on the conclusions.

 

[Emily's Cat]

Which is inherent in my repeated statement of the fact that I'm basing this off a logical principle.

You are continuously mis-stating my argument, presenting made-up nonsense as my argument, and refusing to acknowledge arguments I have made. GIVE ME A REASON to back down a teensy bit.

What reasons? What have I failed to acknowledge? Let's see...

1) First, I objected to the universality, and simultaneously provided alternative wording that does completely cover the situations you've described for application of absence of evidence.

Logically, this isn't true. Lack of evidence is NOT evidence of lack. This is an established proposition for argumentation.

Lack of expected evidence is sufficient reason to reject a claim.

You responded by literally declaring that I was wrong. Now, you did also say:

IN GENERAL lack of evidence is not evidence of a lack, sure. But a lack of evidence that is necessary due to the hypothesis, despite repeated systematic analysis, is evidence for that hypothesis being wrong. If the hypothesis is "bigfoot exists", that means that the lack of bigfoot remains counts as evidence against bigfoot's existence.

but you also went on to toss about some snide implied insults too, but hey, whatever. At that point, I'm fairly certain that I DID acknowledge your points, and pretty explicitly too:

I understand what you're say, Dinwar. I don't even disagree with this approach as a valid methodology. But it isn't logic; it's deductive reasoning. It's shorthanding "The probability of non-avian dinosaurs existing after the K/Pg boundary is vanishingly small, therefore, it is reasonable to deduce that there are none"

And that's a perfectly valid thing to do. It is pragmatic and sensible, and has enormous utility.

And yet... "Lack of evidence" does not incontrovertibly equate to "evidence of lack".

Lack of evidence given sufficient rigor and research is sufficient to deduce lack. But lack of evidence is not evidence of lack.

See the salient points: absence of something isn't "evidence" in any common usage of the term, and an admittedly nit-picky distinction between formal logic and deductive reasoning. One relies on absolutes, the other on most likely.

At that point... you pretty much dug your heals in as if I hadn't understood you at all, despite my explicit acknowledgment of the validity of that approach in that context.

Heck, I even tried to soften my approach, and tried to be even more clear, and reiterated that the topic of the discussion is not specifically bigfoot, but the application of logic:

Dinwar, I've tried to be clear, but I think I'm failing

In your specific line of work, in this specific context, it is sufficient to deduce a lack of existence based on a lack of evidence.

Outside of specific contexts, however, it is NOT sufficient. It is not universally true. You cannot say "lack of evidence is evidence of lack" as a generality.

...

This thread is about logical fallacies. In order to discuss logical fallacies, we need to begin with formal logic.

Holy cow. I've said several times now that in the context of bigfoot, it's perfectly reasonable to deduce nonexistence in this fashion. I've repeatedly, over and over, specified that it's not universally true in all contexts.

What exactly do you think I've failed to say that would smooth your ruffled feathers?

I assume, by your response, that you did not google the concept "Strong Inferrence"?

I did. It is described as a method for testing multiple alternative hypotheses simultaneously, and in a rigorous fashion. What is it that you think is actually relevant here?

Pretty much, yeah, though you've stated both in the worst possible light.

...

The fact that you wish to present my arguments in the worst possible light

As opposed to the open-minded and gracious way in which you've considered my points?

That's right. However, it's a vital nuance. Your view is not practical, is not applied by literally ANYONE outside the most ivory-tower philosophers in the most formal settings, contradicts common usage, and encourages the sort of intellectual slovenliness that characterizes the worst aspects of this forum.

No, it's not. It's really not. Our disagreements are over how, fundamentally, to apply logic--you taking, as far as I can tell, a very rule-based approach, while I focus on the principles guiding those rules. Note that I keep referencing a principle for why lack of evidence is evidence of lack, while you keep attempting to establish ad hoc boundaries to it.

Because mistakes like the ones you are making are dangerous. They infect one's thinking in other areas. I see no reason to give you a pass merely because we agree on the conclusions.

Let's see.

Explain to me how it is dangerous, ivory-towerish, and rule-bound, mistakes for me to say (again):

In many cases, an absence of evidence is sufficient to deduce absence of the thing in question, but it's not universally true that absence of evidence is evidence of absence.

Please explain:
1) the mistakes that I'm making
2) the danger involved
3) the rules that I'm so bound to
4) impractical
5) only used by the most ivory-tower philosophers.

 

[catsmate]

I would buy a ticket to that conference, SO MUCH...

As I've heard it, Friends of the Echinoderm had to stop advertising their meetings at GSA for a while (they may still be banned, been a while since I've gone) because the police got tired of breaking up the riots. Plus, we're the only scientific field I know of where explosives have been banned because paramilitary tactics and scientific exploration don't go together....

Well theoretical physics never had the Bone Wars...