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Tuesday, December 31, 2002 ( 11:11 PM ) (Permalink)

What's New?

I've added a "raw", real-life example—in place of the former cooked-up one—to the black-or-white fallacy, drawn from the Guardian article on superstition quoted in yesterday's entry.

Monday, December 30, 2002 ( 11:26 PM ) (Permalink)

Name that Fallacy!

Here's a quote from an article in The Guardian newspaper which seems to show that even animals commit fallacies:

"…[I]t was in 1947 that a dozen pigeons gave researchers at the University of Indiana what was to prove the most fundamental insight into the roots of superstition and magic—even, many would argue, of religion itself. These birds were put on restricted rations, so that before long their body weight had fallen by 25% and they were permanently hungry. When each bird had, in the words of Professor Burrhus Frederic Skinner, been 'brought to a stable state of hunger', it found itself spending several minutes every day in a special cage. At one end of the cage was an automatic food hopper, linked to a timer so that it would swing into place every 15 seconds, and remain in place for five seconds before disappearing.

"Crucial to the set-up was the fact that, no matter what the pigeon did, the food came and went at set intervals. For the purpose of the experiment was to observe what effect its comings and goings had on the pigeons. And, sad to say, it made them—and, by extension, us—look somewhat foolish.

"Before long, one of the pigeons had begun making strange counterclockwise turns in the intervals between the hopper's arrival. Others indulged in repetitive head movements, while two birds developed a complicated pendulum motion of the head and body. By the end of the experiment, six of the eight subjects were performing elaborate routines, clearly with the intention of hastening the return of the food. In each case, the routine grew out of some action that the bird had just happened to be performing when the hopper appeared.

"Describing what is now regarded as a classic experiment, Skinner was in no doubt as to the mechanism involved: 'The bird behaves as if there were a causal relation between its behaviour and the presentation of food, although such a relation is lacking,' he wrote."


Source: Critical Thinking on the Web

Monday, December 23, 2002 ( 1:30 AM ) (Permalink)

What's New?

Just in time for Christmas, the Fallacy Files proudly presents a "Grinching" (a holiday-themed "Fisking") of the famous "Yes, Virginia" editorial! If you still believe in Santa Claus (what are you doing using a computer?), don't go there!

Monday, December 16, 2002 ( 3:02 PM ) (Permalink)

What's New?

A new example for fallacy hunters.

Sunday, December 15, 2002 ( 2:03 PM ) (Permalink)


Eric Anderson writes to the Fallacy Files:

"You classify circular reasoning as being an informal fallacy. I question whether it is formal or informal. But first let me comment on the case you raise of mathematical circular reasoning. …

"You raise the question of why it is not fallacious for a mathematician to reason in a circle. I would respond by saying that each piece of the circle is an individual argument with a conclusion of the form 'Therefore, if Pj is true, then Pj+1 is true'. … None of these individual arguments needs to prove the truth of any individual proposition in order to show that they are all equivalent. There could be equivalent forms of a false claim, as well as equivalent forms of a true claim. Consequently, to prove all of them, or to disprove all of them, the mathematician must still independently establish that at least one of the equivalent forms is true or false. In some cases, this is done simply by citing an earlier result.

"In short, when the mathematician argues 'in a circle' to establish equivalency, this is not by itself a claim of having proved any of the individual equivalent forms of the proposition. I would say that is why it does not commit a fallacy of begging the question. On the other hand, if one claimed to have proven Pj+1 because Pj implies Pj+1 and Pj is true…, etc., then one would be committing the fallacy of begging the question or circularity. But that is not what the mathematician is claiming to show by the circle, which is only equivalence. …

"Now, none of what I have been saying above depends on knowing anything particular about the propositions P1 through Pn. I have discussed it completely in formal/abstract terms. Consequently, I question why begging the question is not a formal error. I suppose it is a matter of semantics, but I would think that a formal error would cover the cases where we could examine the error without regard to the details of the particular propositions. In other words, you don't need to know anything about P1, P2, …, other than their formal relationship to one another. Just as a circle is a shape/structure, a circular line of reasoning seems to be a form of reasoning that is defective regardless of the content of the individual propositions in the circle."

Eric, there are three reasons why I classify circular reasoning as an informal fallacy:

Thanks for the thoughtful question, Eric!

Saturday, December 14, 2002 ( 11:54 PM ) (Permalink)


"Implausibly precise statistics…are often bogus. Consider a precise number that is well known to generations of parents and doctors: the normal human body temperature of 98.6 degrees Fahrenheit. Recent investigations involving millions of measurements have revealed that this number is wrong; normal human body temperature is actually 98.2 degrees Fahrenheit. The fault, however, lies not with Dr. Wunderlich's original measurements—they were averaged and sensibly rounded to the nearest degree: 37 degrees Celsius. When this temperature was converted to Fahrenheit, however, the rounding was forgotten, and 98.6 was taken to be accurate to the nearest tenth of a degree. Had the original interval between 36.5 degrees Celsius and 37.5 degrees Celsius been translated, the equivalent Fahrenheit temperatures would have ranged from 97.7 degrees to 99.5 degrees."
(John Allen Paulos, A Mathematician Reads the Newspaper, Anchor, 1995, p. 139.)

Friday, December 13, 2002 ( 2:04 PM ) (Permalink)

What's New?

I've added a quote to the fallacy of "two wrongs make a right", and fixed a broken link to the example.

( 1:10 AM )

Fallacies in the News

"I'm not the President, but I play him on TV…."

Update (12/10/2007): This article seems to be no longer available online, but it concerned a silly celebrity actor―who happened to play the president of the United States on television―opining on politics.

Name that fallacy!

Tuesday, December 10, 2002 ( 8:59 PM ) (Permalink)


Karen writes to the Fallacy Files with the following query:

"What do you call an argument that depends on using one meaning of a term in the premiss and a different meaning in the conclusion? I was trying to point out such a 'fallacy' (maybe) in a 'net forum discussion on Libertarian philosophy. I read through your site…and couldn't really find a 'home' for it, although it seems to belong somewhere in the 'ambiguity' family. The discussion was several posts long, but I'll spare you the blow-by-blow description and try to briefly recap it:

"I was trying to point out the flaw I'd noted in Libertarian philosophy. The specific cite the poster used was Harry Browne's 'The Unselfishness Trap'. … In general, proponents of the philosophy make an argument that depends on changing the meaning of the term 'selfishness' in the middle of the argument. That is, the meaning that makes the premiss true is not the same meaning used in the conclusion. I called it 'semantic bait and switch' at one point, and 'semantic sleight of hand' at another."

Good names, especially "bait and switch"!

"Specifically, the term 'selfishness' is first defined to mean that all our actions come from 'self'—we do what we do because of who we are, and that it follows that what makes us happy depends on who we are. I doubt any thinking person could disagree with this; who else are you going to be, and how else are you going to define happiness? But then they argue that the logical conclusion of this premiss is that acting only in your own self interest is the 'natural order' of human interaction. In effect, they change the meaning of 'selfishness'—defining it as 'acting from self' for the proposition, then defining it as 'acting for self' for the conclusion.

"The point I was trying to make in the forum was that without this redefinition of 'selfishness,' the whole argument falls apart—that 'selfishness' as redefined is not a logical conclusion of 'selfishness' as originally defined; in terms of acting from self, acting for self is merely one choice that a person acting from self might make."

Saturday, December 07, 2002 ( 1:05 AM ) (Permalink)

What's New?

The fallacy of appeal to consequences is!

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