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.

[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 at Pandas Thumb.

FL, one of their Intelligent Design trolls, is trying to use a quote from 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!

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..._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..._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

[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

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.