A Magical Journey through the Land of Logical Fallacies - Part 1
An examination of many of the most common logical fallacies.
| Skeptoid #73 November 06, 2007 Podcast transcript | Listen | Subscribe |
|
If you've ever had a conversation with anyone about their supernatural or pseudoscientific beliefs, you've almost certainly been slapped in the face with a logical fallacy or two. Non-scientific belief systems cannot be defended or supported by the scientific method, by definition, and so their advocates turn elsewhere for their support. In this episode, we're going to examine a whole bunch of the most common logical fallacies that you hear in reference to various pseudosciences. When you hear one that you recognize, be sure to wave and say hello.
Let's begin with:
The Straw Man Argument
We're starting with this one because it's the most common and also one of the easiest to spot. This is where you state your position, and your opponent replies not to what you said, but to an exaggerated and distorted caricature of what you said that's obviously harder to defend.
Starling says: "People who commit minor offenses should be let out of jail sooner."
Bombo replies: "Emptying out all the jails would create havoc in society."
Well, maybe Bombo's right, but that's not relevant, because "emptying the jails" is not what Starling advocated. In fact Bombo did not refute Starling's point at all — he invented a different point that was easier to argue against. He created a straw man — one of those dummies stuffed with straw that soldiers use for bayonet practice. It's too weak to fight back. And Bombo can then take satisfaction in having made a point that no reasonable person would argue with, and he appears to have successfully defeated Starling's argument, when in fact he dodged it.
Ad Hominem
From the latin for "to the person", an ad hominem is an attack against the arguer rather than the argument. This doesn't mean that you simply call the person a jerk; rather, it means that you use some weakness or characteristic of the arguer to imply a weakness of the argument.
Starling: "I think Volvos are fine automobiles."
Bombo: "Of course you'd say that; you're from Sweden."
Starling's Swedish heritage has nothing to do with the quality of Volvo automobiles, so Bombo's is an attempt to change the subject and is an avoidance of the issue at hand. Bombo is trying to imply that Starling's Swedish heritage biases, and thus invalidates, his statement. In fact, one thing has nothing to do with the other. Ad hominem arguments try to point out fault with the arguer, instead of with the argument.
Appeal to Authority
This type of argument refers to a special authoritative source as validation for the claim being made. Every time you see an advertisement featuring someone wearing a white lab coat, or telling you what 4 out of 5 dentists surveyed said, you're seeing an appeal to authority.
"Acupuncture is valid because it's based on centuries-old Chinese knowledge."
"This article in a peer-reviewed scientific journal says that people are getting fatter."
"A growing number of scientists say that evolution is too improbable."
"Wired Magazine says that Skeptoid is an awesome podcast."
An appeal to authority is the opposite of an ad hominem attack, because here we are referring to some positive characteristic of the source, such as its perceived authority, as support for the argument. But a good authority supports a position because that position has been shown to be otherwise justified or evidenced, not the other way around. If you say that scientists support Theory X, are those scientists claiming that Theory X is true because they believe it? No, good scientists attach no significance at all to their own authority. Theory X needs to stand on its own; an appeal to authority does not provide any useful support.
Special Pleading
An argument by special pleading states that the justification for some claim is on a higher level of knowledge than your opponent can comprehend, and thus he is not qualified to argue against it. The most common case of special pleading refers to God's will, stating that we are not qualified to understand his reasons for doing whatever he does. Special pleadings grant a sort of get-out-of-jail-free exemption to whatever higher power lies behind a claim:
Starling: "Homeopathy should be tested with clinical trials."
Bombo: "Clinical trials are not adequate to test the true nature of homeopathy."
No matter what Starling says, Bombo can claim that there is knowledge outside of Starling's experience or at a level that Starling cannot comprehend, and the argument is therefore ended. Bombo might also point out that Starling lacks some professional qualification to discuss the topic, thus placing the topic out of Starling's reach.
Bombo: "You're not a trained homeopath, so you shouldn't be expected to understand it."
A special pleading makes no attempt to address the opponent's point, it is just another diversionary tactic.
Anecdotal Evidence
One of the most common ways to support just about any non-evidence based phenomenon is through the fallacious misuse of anecdotal evidence. Anecdotal evidence is information that cannot be tested scientifically. In practice this usually refers to personal testimonials and verbal reports. Anecdotal evidence often sounds compelling because it can be more personal and captivating than cold, uninteresting factual evidence.
Anecdotal evidence is not completely useless. You could say "We saw the Bigfoot corpse at such a location", and if that information helps with the recovery of an actual body, then the anecdotal evidence was of tremendous value. But, note that it's the Bigfoot corpse itself that comprises scientific evidence, not the story of where it was seen.
"I know for a fact that ghosts exist. My friend, who is a very reliable person, has seen ghosts on many occasions."
Anecdotal evidence is great for suggesting new directions in research, but by itself it is not evidence. When it is presented as evidence or in place of evidence, you have very good reason to be skeptical.
Observational Selection
Observational selection is the process of keeping the sample of data that agrees with your premise, and ignoring the sample of data that does not. Observational selection is the fallacy behind such phenomena as the Bible Code, psychic readings, the Global Consciousness Project, and faith healing. Observational selection is also a tool used by pollsters to produce desired survey results, by surveying only people who are predisposed to answer the poll the way the pollster wants.
Bombo: "The face of Satan is clearly visible in the smoke billowing from the World Trade Center."
Starling: "And in one of the other 950,000 frames of film, the smoke looks like J. Edgar Hoover; in another, it looks like a Windows XP icon; and in another it looks like a map of Paris."
Remember that one out of every million samples of anything is an incredible one-in-a-million rarity. This is a mere inevitability, but if observational selection compels you to ignore the other 999,999 samples, you're very easily impressed.
Appeal to Ignorance
Argumentum ad ignorantiam considers ignorance of something to be evidence that it does not exist. If I do not understand the mechanism of the Big Bang, that proves that there is no knowledge that supports it as a possibility and it therefore did not happen. Anything that is insufficiently explained or insufficiently understood is thus impossible.
Starling: "It is amazing that life arose through the fortuitous formation of amino acids in the primordial goo."
Bombo: "A little too amazing. I can't imagine how such a thing could happen; creationism is the only possibility."
Using the absence of evidence as evidence of absence is a common appeal to ignorance. People who believe the Phoenix Lights could not have been simple flares generally don't understand, or won't listen to, the thorough evidence of that. Their glib layman's understanding of what a flare might look like is inconsistent with their interpretation of the photographs, so they use an appeal to ignorance as proof that flares were not the cause.
Non-Sequitur
From the Latin for "It does not follow", a non-sequitur is an obvious and stupid attempt to justify one claim using an irrelevant premise. Non-sequiturs work by starting with a reasonable sounding premise that it's hoped you will agree with, and attaching it (like a rider to a bill in Congress) to a conclusion that has nothing to do with it. The sentence is phrased in such a way to make it sound like you have to accept both or neither:
"Corporations are evil, thus acupuncture is good."
"The government is evil, thus UFOs are alien spacecraft."
"Allah is great, thus all Christians should be killed."
When we do science, it takes more than simply connecting two phrases with the word "thus" to draw a valid relationship. Thus, non-sequiturs are not valid devices to prove a point scientifically.
Post Hoc
The idea that some event must have been caused by a given earlier event, simply because it happened later, is post hoc ergo propter hoc — "It happened later so it was caused by". The assumption of cause and effect is the type of pattern that our brains are hardwired to find, and so we find them everywhere. He took a homeopathic remedy, and his cancer was cured — one happened after the other, and so the faulty assumption is that the homeopathy caused the remission.
Starling: "I bought this car from you, and the heater is broken."
Bombo: "It worked before you bought it, so you must have broken it yourself."
Bombo sees that the breakage happened after Starling made the purchase, so he assumes that one caused the other. In fact there are no grounds for such a correlation. Combined with observational selection, faulty post hoc assumptions account almost entirely for the proliferation of alternative therapies and widespread belief in psychic powers.
Confusion of Correlation and Causation
Closely related to post hoc, but a little bit different, is the confusion of correlation and causation. Post hoc assumptions do not necessarily include any correlation between the two observations. When there is a correlation, but still no valid causation, we have a more convincing confusion.
Starling: "Chinese people eat a lot of rice."
Bombo: "Therefore the consumption of rice must cause black hair."
Due to the nature of Chinese agriculture, there is indeed a worldwide correlation between rice consumption and hair color. This is a perfect example of how causation can be invalidly inferred from a simple correlation.
Slippery Slope
A slippery slope argument presumes that some change will inevitably result in extreme exaggerated consequences. If I give you a cookie now, you'll expect a cookie every five minutes, so I shouldn't give you a cookie.
Starling: "It should be illegal to sell alternative therapies that don't work."
Bombo: "If that happened, any minority group could make it illegal to sell anything they don't happen to like."
No matter what Starling suggests, multiplying it by ten or a hundred is probably a poor proposition. Bombo can use a slippery slope argument to exaggerate any suggestion Starling makes into a recipe for disaster.
The slippery slope is probably the most common subset of the larger fallacy, argument from adverse consequences, which is the practice of inventing almost any dire consequences to your opponent's argument:
Starling: "They should remove 'Under God' from the Pledge of Allegiance."
Bombo: "If that happened, all hell would break loose. Students would have sex in the hallways, school shootings would skyrocket, and we would become a nation of Satan worshippers."
That's enough for one day. Any more than this at one sitting would turn anyone into a quivering lump of irrational jelly, just like the one that first took shape in the primordial goo. Next week we'll continue and wrap up our list of logical fallacies. Until then, digest all of these that your system won't reject.
References
© 2009 Skeptoid.com
Discuss!
5 most recent comments | Show all 16 comments
Remember, you should always read with skepticism the comments of anyone too lame to put their real name & city.
I am kind of curious how you did the special voices in the podcast. Were they entirely computer generated or simply a computer modifying words spoken by a person? If the former, I am curious what program you used. They actually sounded a lot more natural than text-to-spoken word generators I have experimented with.
Next, in the spirit of identifying poor arguments, I will accuse Robert of also making something of a straw-man argument. You are unfairly characterizing what I believed to be a well-thought out and evidence-based negative look at criticisms of farm-fishing by only two of many statements. These were meant more to be jokes and satire of the ridiculousness of the arguments in favor of subject matter than serious points.
And to prevent me from being counter-accused of strawing your argument, I acknowledge that you made the point about these statements being simply rhetorical flare. But, suggesting that these were the best, and not the worst, arguments he offered is dishonest.
P.s. still want to know about those voice generators.
Patrick, Orlando
November 22, 2008 3:29pm
Okay, having just read this one, I would like to put it to the test. I'll field a dual question here (using Skeptoid's most heated topic) and invite anybody to give me an answer, without falling into any of the logical fallacies listed in this epidode.
Ready? (I'll try to make this question as clear as possible with a bit of "qualifying intro"):
INTRO
In the ongoing controversy between the two opposing views of Evolution [EVo] and Special Creation [SCr], the first one deals with biological processes and life sciences but also with earth sciences, geological evidences, paleontology, astronomy, physics, and cosmology. SCr also deals with the same fields.
EVo claims organic evolution involving micro and macro sets, and with speciation (separate species diversifying into newer species) and with biogenesis.
SCr accepts microevolution processes, but rejects speciation via macroevolution. EVo has an old-world view; SCr has a young-world view.
QUESTION: (a) If all of the Earth's (and universe) systems and processes which involve these sciences are to be viewed and interpreted in their various dynamic changes, is it fairer to follow the process back as far as possible to a Beginning, and state what that beginning would likely be (thus implying SCr)? OR (b) is it fairer to observe microevolution - which is possible - and state that macroevolution occurs and is inferred in those processes, (thus implying EVo)?
I particularly hope for no Straw Man Arguments here.
Joe Boudreault, Hanover, Ontario, Canada
May 04, 2009 5:53pm
It depends on which you try to confirm; if you don't want to confirm SCr, then don't go all the way back. If you want to prove SCr, go all the way back.
The key to that is knowing that EVo doesn't even remotely claim that it knows how everything was created; if a Deity is necessary and irrefutable, then EVo is simply a very good toolset the Deity could use to make sure the system is self-sustaining.
There should not be a controversy to bein with; EVo could be a suset of SCr's premise, or you can treat them separately and unrelated (with SCr defining the beginning and EVo defining how the Deity's creatures continue with or without Him).
Joseph, Norman
June 08, 2009 8:09am
Yes, Joseph, there are those two possibilities there. But evolution always demands a huge amount of time and creation sticks to the straight and narrow of young time.
I want to engage in a conversation or discussion of the possibility that we live in a very young universe (ie 10,000 years) as opposed to an ancient evolving universe. I believe the science supports only a young universe. Who's willing to debate this seriously?
I wish to confirm that special creation is the answer which supports the scientific evidence which we now have and can see before us.
A logical fallacyn is one in which the supposed argument says that one point of view is silly and the other poinht of view is valid. Which is true?
Joe Boudreault, Hanover, On, Canada
June 17, 2009 5:19pm
Make a comment about this episode of Skeptoid (please try to keep it brief & to the point). Anyone can post:
You can also discuss this episode in the Skeptoid Forum, hosted by the James Randi Educational Foundation.
Join the Skeptalk email discussion list.
What's the most important thing about Skeptoid?
![[Valid RSS]](/images/valid-rss.png "Validate my RSS feed"){kind=small}
Scientific American just posted an interesting article on the Ad Hominem:
http://www.sciam.com/article.cfm?id=character-attack
Rob Hooft, The Netherlands
June 01, 2008 12:19pm