Contextual examples of logical fallacies

[Dr B]

I thought I would start a thread for everyone to post up contextual examples of logical fallacies. This should help all readers here get a better understanding of what fallacies are and how they work.

Can I suggest that people merely pick some simple example arguments (from the literature, their own observations, or even around here) describe them here and then the fallacy that the argument represents. If we get enough here and it seems successful we can make this thread a sticky so that it stays in people's minds so to speak.

This is open to all (newbies and regulars)

I will return with some examples of my own - but just wanted to kick things of with this opening statement.

Note - any discussions of the fallacies (i.e., if we do not totally agree with each other) can be placed in a sister thread. I would rather this thread remained a clear documentation, not just of fallacies, but some nice contextual examples of them. O0

[Jocky]

Hi Doc,

Just to get things started, here's an old chestnut.

My mother recently told me why she believes in Homeopathy. Several years ago she was diagnosed with arthritis. A friend of hers then gave her a bottle of homeopathic pills, and after she took them the pain of the arthritis lessened for a while. She did not claim to have been cured, but she was quite sure that the homeopathic remedy had eased the pain.

I explained to her the difference between anecdotal evidence and that gathered through blinded, controlled trials, but this could not shake her belief that the pills she took had made a difference. "But you see, the arthritis only went away after I took them!" she proclaimed, quite certain that this represented the clinching argument.

The logical fallacy at work here is "Post hoc ergo propter hoc" - the assumption that there is necessarily a causal link between sequential events. Not so: just because one event occurs before another, it is not safe to assume that the former contributed to the latter.

[Mongrel]

There's a lovely Appeal to Authority in this thread (http://pandasthumb.org/archives/2007/12/young-earth-ris.html#comment-137559) at Pandas Thumb.

FL, one of their Intelligent Design trolls, is trying to use a quote from Kurt Vonnegut (http://en.wikipedia.org/wiki/Kurt_Vonnegut) (probably taken out of context) to back his position regarding Evolution.


…Which essentially answers Mplavcan’s question. You see, Vonnegut wasn’t just a influential sci-fi writer. He was an honorary president of the American Humanist Association.

For somebody like of his level of cultural influence to finally come around and be willing to publicly ascribe a measure of merit to design as opposed to natural selection regarding the human body, is no small thing.

[Admin]

Chilly posted this link recently: http://www.dianelloyd-hughes.co.uk/about.php

It contains the claim that Diane Lazarus 'helped the police' in the Jill Dando case.


The Wales on Sunday newspaper also took me to the scene of the Jill Dando Murder and information was then passed onto the Police to assist them in their enquiries. The police later arrested the person who was recently convicted of her murder.Obviously, it's quite clear that her information didn't necessarily contribute to the arrest in any way. To conclude it did is making a simple Post Hoc fallacy.

What I want to discuss here though is whether there's a linguistic equivalent of contiguity (the tendency to assume that events that occur close in space or time are related). If so, what is it called?

I think that writing statements close together like that gives the illusion of contiguity "I gave info to the police. The police made an arrest". i.e. the deliberate linguistic pairing of two unconnected events can make them appear to be linked or that one led to the other.

Our propensity to make connections between things that occur together could make these two statements look a lot more convincing than they actually are.

It looks like a good way to encourage people to form a false conclusion without the writer actually having claimed anything.

[Lord Muck oGentry]

John,

You may find this interesting, especially the section on the Cooperative Principle:
http://plato.stanford.edu/entries/implicature/

[Admin]

Thanks for that Lord Muck! O0

Yes, that looks like the sort of thing that is going on. There's more than just a simple logical fallacy. Lazarus does not say that her information led to the arrest but by the way it's presented, she certainly implies it. It's the conclusion she wants people to make.

[Lord Muck oGentry]

Here is a beauty:
http://www.conservapedia.com/Logical_fallacy#Your_theory_does_not_work_under_my _theory.2C_so_your_theory_must_be_wrong

This fallacy occurs when one theory is judged by the premises and assumptions of another theory, rather than against its own premises and assumptions. This form of fallacy follows the form:

* Theory A says that if P then Q
* Theory B says that if P then R
* Therefore theory A is wrong

For example: "Dinosaurs died 65,000,000 years ago, so the earth couldn't have been created 6,000 years ago."

Not so much nonsequitur as anacoluthon. In the first place, the " example" does not " follow the form" of the supposed fallacy ( does the author actually understand the word form?). In the second place, judging a theory " against its own premises and assumptions" is better known as circular reasoning. In the third place... Oh, bugger it, I give up!

The real joy of this one is that it comes from a site solemnly purporting to explain fallacious reasoning.

[Mongrel]

Here is a beauty:
http://www.conservapedia.com/Logical_fallacy#Your_theory_does_not_work_under_my _theory.2C_so_your_theory_must_be_wrong


Not so much nonsequitur as anacoluthon. In the first place, the " example" does not " follow the form" of the supposed fallacy ( does the author actually understand the word form?). In the second place, judging a theory " against its own premises and assumptions" is better known as circular reasoning. In the third place... Oh, bugger it, I give up!
Sounds like a creationist argument attempt (if I'm reading it right) "If we can prove Evolutionary theory wrong then creationism\ID is right!"


The real joy of this one is that it comes from a site solemnly purporting to explain fallacious reasoning.

My irony meter broke again :-[

I'm guessing this came about after the editor of conservapedia got pwned (to use the vernacular) by an Evolutionary Biologist
(http://pandasthumb.org/archives/2008/06/lenski-gives-co.html) ;D

[Lord Muck oGentry]

Sounds like a creationist argument attempt (if I'm reading it right) "If we can prove Evolutionary theory wrong then creationism\ID is right!"



My irony meter broke again :-[

I'm guessing this came about after the editor of conservapedia got pwned (to use the vernacular) by an Evolutionary Biologist
(http://pandasthumb.org/archives/2008/06/lenski-gives-co.html) ;D

Excellent link! I particularly enjoyed this bit:

P.P.P.P.S. I noticed that you say that one of your favorite articles on your website is the one on "Deceit." That article begins as follows: "Deceit is the deliberate distortion or denial of the truth with an intent to trick or fool another. Christianity and Judaism teach that deceit is wrong. For example, the Old Testament says, 'Thou shalt not bear false witness against thy neighbor.'" You really should think more carefully about what that commandment means before you go around bearing false witness against others.

As we say in Glasgow: Ye couldnae shame these craiturs!

[vbloke]

I find creationism to be a form of Ignotum Per Ignotius.
Explaining the unknown by the unknowable.

[MollyMac]

From the Humanist Society of Scotland's Primary Education Resource Package:


The Golden Rule is used in so many religions that it must be a very good rule.argumentum ad populum

[Lord Muck oGentry]

The Decoy Duck is one of my favourites.

We don't need telling that a decoy duck, unlike a brown duck, isn't a duck. Or that a forged fiver isn't a fiver, or that a fake Rembrandt isn't a Rembrandt. The adjective warns us off.

But there are related adjectives that neither beckon us on nor warn us off. For example, an alleged murderer may be a murderer, but he needn't be. An apparent obstacle to our plans may turn out to be an obstacle, but it needn't. Or an arguable case may turn out to be unanswerable —or no case at all.

Adjectives of this second sort seem to attract bad arguments. For example, in many debates about abortion, there will be at least one participant who thinks that if a foetus is a potential person then it simply must be a person. Well, if it is, that isn't the way to prove it.
Similarly, in political debates about the passing or repealing of controversial measures, there is sure to be someone who thinks that if he can point to a perceived injustice, he has thereby identified an injustice. It doesn't occur to him that the perception may be wrong.
Or— to get onto territory familiar to skeptics— there are those who will insist that if they have had subjective experience of ghosts or psi or pixies, then they have had, in the ordinary sense, experience of these things. It never occurs to them that a similar argument could be applied to the drunkard's pink elephants.

Any of these arguments can be attacked in other ways. But when I see one of the dangerous adjectives, I like to ask: decoy duck, brown duck or alleged duck?

[bindeweede]

The Decoy Duck is one of my favourites.

We don't need telling that a decoy duck, unlike a brown duck, isn't a duck. Or that a forged fiver isn't a fiver, or that a fake Rembrandt isn't a Rembrandt. The adjective warns us off.

But there are related adjectives that neither beckon us on nor warn us off. For example, an alleged murderer may be a murderer, but he needn't be. An apparent obstacle to our plans may turn out to be an obstacle, but it needn't. Or an arguable case may turn out to be unanswerable —or no case at all.

Adjectives of this second sort seem to attract bad arguments. For example, in many debates about abortion, there will be at least one participant who thinks that if a foetus is a potential person then it simply must be a person. Well, if it is, that isn't the way to prove it.
Similarly, in political debates about the passing or repealing of controversial measures, there is sure to be someone who thinks that if he can point to a perceived injustice, he has thereby identified an injustice. It doesn't occur to him that the perception may be wrong.
Or— to get onto territory familiar to skeptics— there are those who will insist that if they have had subjective experience of ghosts or psi or pixies, then they have had, in the ordinary sense, experience of these things. It never occurs to them that a similar argument could be applied to the drunkard's pink elephants.

Any of these arguments can be attacked in other ways. But when I see one of the dangerous adjectives, I like to ask: decoy duck, brown duck or alleged duck?

Lord Muck,

I think you are very right about what I might call "adjectives of implication" - you mention "alleged", "apparent", "arguable", "potential". Mr Murat has been a victim of this kind of thing. And the tabloid press thrives on it.

Sadly, I think the BBC News is becoming as bad.

Sorry for rambling. It is what I do......

[Lord Muck oGentry]

Absolutely, bw! " Alleged" faces in whichever direction the user or the hearer likes.

[bindeweede]

"Alleged" faces in whichever direction the user or the hearer likes.

Me likee. Am writing it down ATM.:smiley:

[Tony Williams]

I came across a classic the other day on another forum, from someone defending his belief that there could be an alien origin to UFOs:


"Prove that they aren't real! You can't do it. There's no evidence that they exist, but no evidence that they don't exist."

Naturally I responded:


It is faulty logic to demand proof of the non-existence of a highly improbable event (alien visitations). All of the onus of proof lies on those who claim that UFOs have anything other than human or natural causes.

Remember what I posted earlier: "extraordinary claims require extraordinary proofs". Well, a claim that there are aliens flying around in our skies is certainly extraordinary, and therefore requires an extremely high level of evidential proof before it could be taken seriously. No UFO sightings reported so far come even remotely close to that.

[Mulder]

I came across a classic the other day on another forum, from someone defending his belief that there could be an alien origin to UFOs:


"Prove that they aren't real! You can't do it. There's no evidence that they exist, but no evidence that they don't exist."


On the other hand, there IS good evidence that UFO sightings are caused by the misinterpretation of a large number of different aerial phenomena, from balloons to satellites.

[Tony Williams]

On the other hand, there IS good evidence that UFO sightings are caused by the misinterpretation of a large number of different aerial phenomena, from balloons to satellites.

Certainly - that point had been made earlier in the thread.

I feel that the attitude of so many people to topics like this reflects the subtitle of the latest X-Files film: "I want to believe"!

[Dr B]

It all comes down to the fact that most woo's have never been taught, or are not familiar with informal logic.

I tried to teach some people from another association about this a couple of years ago and the association nearly imploded!!!!! Even members of the committee showed their complete ignorance on the matter.....shame really.

[Allo Allo]

On the other hand, there IS good evidence that UFO sightings are caused by the misinterpretation of a large number of different aerial phenomena, from balloons to satellites.

But some can't be explained as mis-interpretations - so this is not really evidence they don't exist. This is an illogical argument to the guy who says you can't prove they don't exist because, on the other hand, there ARE examples of unidentified flying objects that don't fall into the category you put forward... God, I'm even confusing myself! It's the logic - not the UFOs I'm trying to get straight here....:confused:

[Tony Williams]

Bearing in mind that the overwhelming majority of UFO reports have been found to have non-alien causes, it is reasonable to suppose (without convincing evidence to the contrary) that the same will be true of the remainder - if sufficient evidence exists to reach any conclusions at all.

After all, there is no proof that the residue of unexplained UFO sightings is not the Flying Spaghetti Monster having some fun with us...

[Tim the Mage]

But some can't be explained as mis-interpretations - so this is not really evidence they don't exist. This is an illogical argument to the guy who says you can't prove they don't exist because, on the other hand, there ARE examples of unidentified flying objects that don't fall into the category you put forward... God, I'm even confusing myself! It's the logic - not the UFOs I'm trying to get straight here....:confused:

If it's flying and I don't know what it is...? An UFO!

[Allo Allo]

It all comes down to the fact that most woo's have never been taught, or are not familiar with informal logic.


Ordinary people have never been taught, or are not familiar with informal logic. I know nothing about the education system in UK - is any kind of logic ever taught in schools?

[Allo Allo]

If it's flying and I don't know what it is...? An UFO!

;D of course! but its a GAP - so the residue of unexplained UFO sightings is not the Flying Spaghetti Monster having some fun with us but an alien civilisation doing the same. We all know there are not really Flying Spagetti Monsters - no evidence - but there is evidence that some UFO sightings are some thing other than balloons, clouds etc.They appear to be craft - air craft. So, if you use Occam's razor and cut out all the explanations of balloons and other guesses, if it looks like a craft, is identified as a looking like a craft (by pilots maybe), the simplest explanation is that it is an aircraft - unidentified maybe - but a craft, not an unidentified 'object'. The same would apply to identifying a cup of tea on a table as looking like a cup of tea. If it looks like a cup of tea - then, using occams razor, the best conclusion (cutting out all other explanations such as an illusion, imagination, or fantasy) would be that it is a cup of tea on a table where one would expect a cup of tea to be! That would seem more logical to me.:undecided:

[Dr B]

We all know there are not really Flying Spagetti Monsters - no evidence -

Logically speaking - Does that mean it's impossible?



but there is evidence that some UFO sightings are some thing other than balloons, clouds etc.

Is there? Where? There are a number of different explanations for different instances - but none of these require an ET-type explanation. Can you point us to this evidence?



They appear to be craft - air craft.


Yes - commercial and military



So, if you use Occam's razor and cut out all thee explanations of balloons and other guesses, if it looks like a craft, is identified as a looking like a craft (by pilots maybe), the simplest explanation is that it is an aircraft - unidentified maybe - but a craft, not an unidentified 'object'.

Actually the razor should only be applied to evidence - not merely anecdotal reports. you are falling into the trap of using your prior biases to set up a conclusion in order to argue that the conclusion is the most likely - this is somewhat circular - at least to me. O0

[Allo Allo]

Logically speaking - Does that mean it's impossible? I hope so! :smiley:


Is there? Where? There are a number of different explanations for different instances - but none of these require an ET-type explanation. Can you point us to this evidence? I agree with you that none require ET explanation. Logically - I am trying to exercise logic here - is that explanations of balloons or clouds aren't evidence. So neither side in an argument on UFOs can prove anything - it's pointless.


Yes - commercial and military Is it logical to think that pilots would know what they are looking at if the craft were commercial? I don't know. If use my common sense, military would seem more likely. If it were that.


Actually the razor should only be applied to evidence - not merely anecdotal reports. Yet anecdotal reports are dismissed without evidence as the evidence is an explanation and not evidence. I have seen Occams razor quoted over and over again with the explanation that this removes what is known to be impossible (like ET's or a multidimensional universe) - but do we know what's possible? I don't accept a flying spaghetti monster only because there are not constant reports of flying spagetti monsters being seen, nor videos of them. My common sense tells me that not ALL video recordings necessarily have to be fakes.


you are falling into the trap of using your prior biases to set up a conclusion in order to argue that the conclusion is the most likely - this is somewhat circular - at least to me. O0 Not at all. It sort of followed on from Mulder's post "On the other hand, there IS good evidence that UFO sightings are caused by the misinterpretation of a large number of different aerial phenomena, from balloons to satellites." where I wondered whether 'evidence' was the correct word. 'Explanations' would be a better one? Logically! Whereas a pilot reporting a strange craft behaving abnormally on his transmission and describing what he sees as he is seeing it would seem more like evidence rather than post hoc explanations of what 'might have been'.

I am not replying again if it concerns believing in Alien UFO's. I don't actually know what I think on this issue. So my bias is to listen to everyone! Fortunately it is not life and death to me currently to have any opinion one way or the other! ;D I think its a very fascinating topic. I perceive that skeptics fall down in their arguments 'against' by what I have tried to explain in my posts.

[Tim the Mage]

I hope so! :smiley:

I agree with you that none require ET explanation. Logically - I am trying to exercise logic here - is that explanations of balloons or clouds aren't evidence. So neither side in an argument on UFOs can prove anything - it's pointless.

Is it logical to think that pilots would know what they are looking at if the craft were commercial? I don't know. If use my common sense, military would seem more likely. If it were that.

Yet anecdotal reports are dismissed without evidence as the evidence is an explanation and not evidence. I have seen Occams razor quoted over and over again with the explanation that this removes what is known to be impossible (like ET's or a multidimensional universe) - but do we know what's possible? I don't accept a flying spaghetti monster only because there are not constant reports of flying spagetti monsters being seen, nor videos of them. My common sense tells me that not ALL video recordings necessarily have to be fakes.

Not at all. It sort of followed on from Mulder's post "On the other hand, there IS good evidence that UFO sightings are caused by the misinterpretation of a large number of different aerial phenomena, from balloons to satellites." where I wondered whether 'evidence' was the correct word. 'Explanations' would be a better one? Logically! Whereas a pilot reporting a strange craft behaving abnormally on his transmission and describing what he sees as he is seeing it would seem more like evidence rather than post hoc explanations of what 'might have been'.

I am not replying again if it concerns believing in Alien UFO's. I don't actually know what I think on this issue. So my bias is to listen to everyone! Fortunately it is not life and death to me currently to have any opinion one way or the other! ;D I think its a very fascinating topic. I perceive that skeptics fall down in their arguments 'against' by what I have tried to explain in my posts.

I don't think anyone is trying to hide from evidence becuase there isn't any solid evidence supporting UFOs. However, the onus is on proving the existence of these alien spacecraft not by playing with statistical approaches and shouting 'gap' all the time. The presence of unexplained phenomena cannot be taken as proof of alien visitation. Which isn't at all the same as saying we haven't been visited by aliens - all we can say is that there is no proof of this happening.

Surely Occam's razor says that ceteris paribus the most likely explanation from the evidence is most likely to be the truth. Which means the answer isn't aliens or bug-eyed monsters but natural or technical phenomena.

[Tony Williams]

Many years ago there was a programme on UFOs on UK TV. It was that rare thing, a good one - in that the producer didn't take the "mystical" approach but rather the hard-headed "let's look for evidence".

One of the examples was quite remarkable. A chap was on an internal flight with his cine camera and filmed out of the window. When the film was processed he had a shock. The film appeared to show a lens-shaped craft which approached the plane at terrific speed, hovered for a moment beside it and then zoomed away again equally quickly. The image was sharp and clear, and a pattern of irregular markings could clearly be seen around the rim of the craft. Now I've alway been a sceptic but, even so, I was impressed and rather shaken - I'd never seen anything so convincing before.

Fortunately, the producer (who deserved a medal) did the right thing: he borrowed the chap's camera, loaded it with the same kind of film, gave it to a TV cameraman who sat in the same seat on the same plane on the same route, and awaited results. What was discovered was a salutary lesson. It turned out that the edge of the window was bevelled, and this had the effect, when the camera was held in exactly the right position, of distorting the view so that a part of the tailplane appeared to be detached from the rest of the plane, the optical aberration causing it to form a lens shape. The markings around the rim were where paint had worn away on the leading edge of the tailplane. Just by moving the camera slightly it was possible to make this "craft" appear and disappear, apparently at high speed.

The lesson is that it really doesn't matter how good photographic evidence is (let alone eye-witness evidence, which is hopelessly unreliable as we've discussed on another thread). To prove that a sighting is of a craft which does not have a human origin requires a very high level of evidence, with corroboration from multiple sources.

[Mulder]

... Not at all. It sort of followed on from Mulder's post "On the other hand, there IS good evidence that UFO sightings are caused by the misinterpretation of a large number of different aerial phenomena, from balloons to satellites." where I wondered whether 'evidence' was the correct word.

The point I'm making is this:

a) people see things they cannot identify in the sky - I think we can all agree on that
b) it is entirely possible that if other observers saw the same object they would recognise it as a known object
c) there is no positive evidence to suppose that if someone sees something they cannot identify in the sky, it is an alien space craft - that is just an assumption drawn from popular culture

Though there are cases involving apparent sightings of aliens and abductions and so on, none stands up to close scrutiny. We still await the space ship landing on the White House lawn! If that happened, we'd have to believe!

[Lord Muck oGentry]

http://www.guardian.co.uk/science/blog/2008/sep/11/michael.reiss.creationism/print

Nice example of False Opposition:

I feel that creationism is best seen by science teachers not as a misconception but as a world view.
It is both a world view and a misconception.



Nice example of Conflation and Warm Words:

I do believe in taking seriously and respectfully the concerns of students who do not accept the theory of evolution, while still introducing them to it.
Well, the concerns of Flat-Earther students too ought to be treated with great seriousness. And with no respect at all.

[Lord Muck oGentry]

Pendant to post #12 and the pitfalls of potential and related words:
http://forums.randi.org/showthread.php?t=134845


But what got me thinking about this (and I can see arguments for both sides) is this: the act of choosing not to have kids in your lifetime means that someone who would have existed does not exist because of your action.

Before seeing this, I should not have thought it possible, except as a joke, for anyone to confuse possible persons with persons. Oh well— wrong again. And not for the last time, either.

As Xavielly Tartakower once observed of the chessboard: " The blunders are all there, waiting to be made."

[Admin]

He's actually correct. ???

However, looking at the linked to post - I'm too tired to wade through that and try to make sense of it at the moment. ;D