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February 27th, 2006 (Permalink)


What has 100 legs, 10 eyes, 1 tail, and purrs?


February 24th, 2006 (Permalink)


Q: [T]here appears to be a fallacy that is not included [in the Fallacy Files]: the treatment aetiology [or "etiology"] fallacy. This fallacy refers to falsely assuming that because taking a drug treats an illness, lack of it is therefore the cause of an illness. A common example would be inferring that serotonin abnormalities cause depression because taking selective serotonin reuptake inhibitors (e.g. Prozac) treat depression. The best counter-example is the classic:

Taking aspirin treats headaches.
Therefore, a lack of aspirin causes headaches.

This is obviously absurd. The fallacy appears to be a type of Non Causa Pro Causa, possibly Post Hoc, Ergo Propter Hoc. Is there a reason for this fallacy not being included? Perhaps because it is simply a typical causational fallacy?
―M. J. Parnell, UK

A: The reason that it is not included is that I hadn't heard of it. It appears to be a type of error specific to medicine, and perhaps identified and named by physicians. It doesn't commonly occur in books on logical fallacies; in fact, I have never come across it in any such source. I assume that it is most likely to be discussed in medical textbooks.

You are right to classify it as a type of Non Causa Pro Causa fallacy because that is the most general category of causal fallacy. However, it wouldn't be a type of Post Hoc, since that fallacy is committed by inferring that one event causes a second because the first event precedes the second. For instance, applying this to your example, it would be Post Hoc reasoning to infer that taking aspirin causes headache relief, though that is presumably correct. Note that in the treatment etiology fallacy one infers that not taking aspirin causes the headache. I suppose that you could say that the non-taking of the aspirin is an event that precedes the headache, but if non-taking of aspirin is an event then so are non-headaches, and many more non-aspirin-takings precede many more non-headaches than non-aspirin-takings precede headaches! In which case, one could conclude a fortiori that lack of aspirin prevents headaches.

I suspect that it would be a reasonable rule of thumb in medical research to hypothesize that a deficiency in a substance is the cause of a disease when supplying that substance treats it. Of course, the hypothesis would have to be tested before concluding that this is really so. There are, of course, vitamin deficiency diseases such as beriberi, ricketts, and scurvy which support this rule of thumb. However, applying the rule of thumb as if it were a universal generalization without exceptions would commit the fallacy of sweeping generalization.

My only doubt about this fallacy is whether it is common enough, and general enough, to warrant being considered a logical fallacy, as opposed to a mistake in medical research. Nonetheless, thanks for drawing it to my attention!

February 22nd, 2006 (Permalink)

More on Breaking the Spell

The New York Times has an odd review of Daniel Dennett's new book Breaking the Spell by Leon Wieseltier of the New Republic. Much of it sounds like a series of straw men, though I can't be certain as I haven't yet read the book. Wieseltier accuses Dennett of committing the genetic fallacy:

And why is Dennett so certain that the origins of a thing are the most illuminating features of a thing, or that a thing is forever as primitive as its origins? Has Dennett never seen a flower grow from the dust? Or is it the dust that he sees in a flower? …

It will be plain that Dennett's approach to religion is contrived to evade religion's substance. … You cannot disprove a belief unless you disprove its content. If you believe that you can disprove it any other way, by describing its origins…, then you do not believe in reason.

This sounds as though Wieseltier has a grasp of what's wrong with the fallacy, but in the remainder of the paragraph, he seems to commit the very fallacy he has just denounced:

Dennett's natural history does not deny reason, it animalizes reason. It portrays reason in service to natural selection, and as a product of natural selection. But if reason is a product of natural selection, then how much confidence can we have in a rational argument for natural selection? The power of reason is owed to the independence of reason, and to nothing else. (In this respect, rationalism is closer to mysticism than it is to materialism.) Evolutionary biology cannot invoke the power of reason even as it destroys it.

So, if human reason has its origin in natural selection, then it loses its "independence"―whatever that is―and "power", and is destroyed. However, it is due to its "power" that reason would be selected for, if not its independence. In other words, reason contributes to human survival because it helps us to figure out the truth. Such an evolutionary explanation of the origins of human reason does not undermine reason because if it did it would undermine the explanation itself.

No matter what our religious beliefs are, we should all be able to agree that at least some religious beliefs are irrational―in the era of the suicide bomber, this should not be controversial. Surely, it's this element of irrationality that makes these beliefs puzzling and in need of explanation. It's not hard to see why we evolved to be reasonable, but how in the world did we evolve to believe such nonsense?

This problem has an interesting relationship to fallacy studies, since in studying logical fallacies we are studying common ways in which human beings are irrational. It is easy to see why we evolved to reason using, say, Barbara, but why in the world would we have evolved to reason with undistributed middles? An animal that reasons by affirming the consequent, is likely to end up as a meal for one that reasons using modus ponens. For this reason, I'm eager to read Dennett's book, as it may cast some light in passing on the evolution of fallacious thinking.

Source: Leon Wieseltier, "The God Genome", New York Times, 2/19/2006

Resource: Baggini on Dennett on Religious Belief, 2/8/2006

Update (2/23/2006): Philosopher Brian Leiter has a harsh review of Wieseltier's harsh review. His main complaints are Wieseltier's sneering tone (which is the pot calling the kettle black, but then there's nothing logically wrong with that!) and his lack of credentials for reviewing a book in philosophy. Interestingly, Leiter seems to think that Dennett gives a genetic argument, but not a fallacious one:

[Wieseltier] does not seem to realize that an account of the historical genesis of a belief can have bearing on the epistemic status of that belief, that beliefs with the wrong kind of etiology are epistemically suspect. But quite apart from the banal epistemic point, the material quoted by Mr. Wieseltier suggests that Professor Dennett's concern is not purely epistemological, but also rhetorical and psychological: namely, how does one get people to give up on religion? Like Nietzsche (and perhaps, in a different way, Hume), Dennett apparently puts his hopes in a convincing historical narrative. …

It is true that you cannot show a belief to be false by explaining its origin, but it is clear you can show that holding the belief is not warranted by explaining its origin. … If you believe buying stock in High Tech Miracle, Inc. is a good investment based on recommendation of your broker, and then you discover that your broker recommended it because he is an investor in the company and a beneficiary of its rising stock fortunes, you no longer have a reason to believe it's a good investment―though it might turn out to be one, of course, but you no longer are warranted in believing that.

From Leiter's language―namely, "suggests" and "apparently"―I presume that he has not read Dennett's book, either, and is relying on Wieseltier's account of it, which is probably a mistake. He gives a good example of a nonfallacious argument which criticizes a belief by attacking its origin, for when dealing with testimony―as opposed to argument―one has to rely upon the credibility of the source. So, to the extent that religious beliefs have their source in testimony, criticism of the source of the testimony is logically legitimate.

As with all informal fallacies, there are cogent arguments with the form of a genetic fallacy. So, one has to examine the content of the argument to determine whether a fallacy is committed. To do so, we must go to the source, which is Dennett's book. I hope to do that soon.

Source: Brian Leiter, "Why Review a Book When You Can Sneer?", Butterflies and Wheels, 2/19/2006

February 18th, 2006 (Permalink)

Water, Water Everywhere

So-called "psychic" detectives usually make vague statements to the police about the locations of missing persons which can later be interpreted as "hits" no matter where they turn up, assuming they're ever found. Here's a case in point:

On television show Sensing Murder last night, mediums Sue Nicholson, Kelvin Cruickshank and Australian Scott Russell-Hill independently identified an area of bush about six metres south of a carpark at McLaren Falls as the spot where [Luana "Laverne"] Williams' body lay. Her disappearance on June 5, 1986, aged 25, has remained unsolved since it was re-opened as a homicide inquiry in 1994. …

The psychics confirmed only what some in the Williams' family already believed. Younger sister Melanie, who lives in Australia but has come home to support her family, said she had a "gift" that had already helped her understand her sister's death. She has already approached police with information "communicated" to her about the McLaren Falls site. …

Ms Williams said family members were frustrated police did not take psychic visions more seriously. She had a vision of "a bridge and water" similar to one experienced by a psychic on the show but she did not go to police, as she expected them to dismiss it. This was confirmed by Detective Warren Gerbich on the show when he said: "A bridge and water, that's New Zealand…Everything is close to a bridge and water."

Source: Rachel Tiffen, "Police Reject Psychic Advice", Bay of Plenty Times, 2/1/2006

Resource: "Not Ready for 'Primetime'", 4/16/2004

Via: Robert Todd Carroll, "Rational Police Frustrate Irrational Citizens", Skeptic's Dictionary Newsletter 64, 2/16/2006

Fallacy: Vagueness

February 14th, 2006 (Permalink)

What's New?

The Fallacy Files is now all natural! No preservatives! No artificial flavors! No artificial colors! Now, with new appeal to nature!

Update (2/17/2006): You may see a Google ad in the scrolling pane to the left for a school that teaches homeopathy. One of the problems with Google's ads is that they use Google's indexing of the page to pick ads that should be relevant to the page's content. This means that if you criticize homeopathy by name, as I did last November, then you will get a lot of ads from Google advertising homeopathic remedies. In this case, it appears to be the words "nature" and "natural" which have triggered this ad, since the school calls itself a "college of natural health". This name is a good example of an appeal to nature which exploits the vagueness of "natural", since it's hard to see what's particularly natural about homeopathy. Normally, I would remove such an ad, since the ads are supposed to offer products that might interest critical thinkers, as well as help defray the expenses of maintaining the files. However, I have left this ad alone, as it's unusually honest:

Blank College of
Natural Health
offers BS…

Resource: "Bad Science Theatre 2005", 11/26/2005

February 11th, 2006 (Permalink)

Check it Out

There's a new book out by Steven Poole entitled Unspeak which appears to be concerned with the political use of doublespeak and loaded language. I haven't read it, but the Guardian has just published a rather unfavorable review. However, the review was written by Alastair Campbell, a former press secretary and communications director for Tony Blair, so he may be a little biased!

P.S. I especially like the P.S.

Source: Alastair Campbell, "We Must Talk", Guardian, 2/11/2006

Fallacy: Loaded Language

February 8th, 2006 (Permalink)

Baggini on Dennett on Religious Belief

Philosopher Julian Baggini, who used to write the excellent "Bad Moves" column, has written a short comment―not a full-fledged review―on philosopher Daniel Dennett's new book Breaking the Spell: Religion as a Natural Phenomenon. The title of the article, "Should we treat religion as a science?"―which I suspect was supplied by an editor, rather than by Baggini―is misleading, since the question is not the silly one of whether to treat religion as a science. Of course not! Rather, the question is whether to scientifically study religious thought as we do other natural phenomena. Of course! Why not? Religious thinking, as all thinking, is a natural phenomenon. What else could it be?

However, Baggini rightly warns against using scientific explanations of the origin of religious beliefs to commit the genetic fallacy. This is a common philosopher's fallacy in which an idea is rejected as irrational because it originates from some non-rational process. This type of argument is fallacious because all ideas can ultimately be explained in terms of some non-rational process―such as electrochemical reactions in the brain. So, if this type of argument were cogent, then all ideas would be irrational, including this type of argument itself. So, if it were cogent, then it wouldn't be cogent! Not having read Dennett's book, I don't know whether he commits this fallacy, but based on having read other works of his, I rather doubt it. Moreover, Baggini doesn't actually say that he does. Nonetheless, it's a common enough mistake to be a logical boobytrap.

Source: Julian Baggini, "Should we treat religion as a science?", Guardian, 2/7/2006

Update (2/9/2006): Adam Kirsch has reviewed Dennett's book in the New York Sun. I've never heard of Kirsch―which is no criticism, but I don't know what his background is, and the article doesn't have a biographical note. He accuses Dennett of committing a fallacy, though Kirsch calls it "the genealogical fallacy". However, I can't tell from the following confusing description whether this is supposed to be the same as the genetic fallacy:

[I]n his application of evolutionary biology to religious practice, Mr. Dennett falls prey to the common fallacy of neo-Darwinists, which might be called the genealogical fallacy: the assumption that a human phenomenon can be fully explained by an explanation of its origins. Drawing on recent, speculative work by evolutionary theorists, Mr. Dennett sketches a picture of how religion might have arisen as a naturally selected adaptation to the early human environment. … But even if such Darwinian just-so stories were confirmed…it would make no difference to the fact of religious experience. Mr. Dennett believes that explaining religion in evolutionary terms will make it less real; that is the whole purpose of his book. But this is like saying that because water is made of two parts hydrogen and one part oxygen, it is not really wet; or because the color red represents a certain frequency of light, it is not really red. To human beings, the wetness of water, the redness of red, is existentially prior to their physical composition. Just so, the reality of religious experience cannot be abolished by explaining it as an adaptation to our prehistorical environment.

There's an ambiguity in talking about the "fact" or "reality" of religious experience. Surely, Dennett doesn't mean to deny that there are such things as religious experiences; otherwise, there wouldn't be anything to explain. Of course, an explanation of religious experience cannot deny the fact or reality of religious experience in this sense, since it presupposes it. However, in another sense, the "fact" or "reality" of religious experience may refer, not to the experiences themselves, but to some supposed object of those experiences, such as God or the supernatural. An explanation of religious experiences could undermine their reality in this sense if it made no reference to the supernatural, just as an explanation of alien abduction experiences could undermine their "reality", in the second sense, if it made no reference to aliens.

So, I doubt that the "genealogical fallacy" is a common error, since in one case it isn't common, and in the other case it isn't an error. In any case, it doesn't sound like the genetic fallacy, which is the endorsement or condemnation of an idea because of its past association with some favored or disfavored thing. Often, it takes the form of believing that something once associated with an idea is somehow passed down―"genetically", as it were―to the present. For instance, it is a genetic fallacy to argue that if an idea has a non-rational origin, then it must continue to be non-rational. Whether an idea is rational depends upon what evidence is for or against it now.

Meanwhile, Salon has published an interview with Dennett by Gordy Slack―whom I don't know from Adam―in which he discusses the book. He doesn't appear to commit the genetic fallacy in the interview, or the fallacious argument attributed to him by Kirsch, so Kirsch may be committing a straw man fallacy. However, I can't be sure without reading the book.

As in Baggini's case, both articles have bad titles, presumably provided by editors who don't understand what they're about.


Update (2/10/2006): John Congdon writes in with the following comments―since his remarks are long, I have interpolated my replies:

Baggini's comment "Science can show a correlation between religious belief or experience and natural phenomena, but that doesn't prove that a sense of God's presence is nothing more than a function of a suitably stimulated brain" is very much on point. He seems to be pointing out that Dennett may be committing (as do so many critics of religion) the informal fallacy non causa pro causa. Specifically, this is cum hoc, ergo propter hoc, taking the form "Mystical experience is accompanied by certain brain activity. Therefore, certain brain activity causes mystical experience."

I suspect that Dennett's view would be that the brain activity just is the mystical experience, rather than causes the experience, for the reason that all experiences are activities in the brain. Of course, this fact tells us nothing about what in the world if anything outside the brain is causing the activity. So, I doubt that Dennett is committing a causal fallacy, though the proof is again in the reading of his book, which I still haven't done!

The further implication, that mystical experience is therefore not "real", is also dependant on bad logic. This might be phrased thus:

In order to be real, a mystical experience cannot have a physical cause.
Mystical experiences have physical causes.
Therefore, mystical experiences are not real.

There is no problem with the form of this syllogism, but since the first proposition is debatable and the second is itself false (at least, insofar as it depends on the cum hoc, ergo propter hoc assertion), the argument is fallacious.

It would certainly be unsound if one or more premisses are false, but not, at least for that reason, fallacious. Not every unsound argument is fallacious.

Baggini may be correct in his suggestion that "Perhaps that [brain activity] is simply the mechanism by which the real God makes himself known." However, he is quite correct in phrasing this as an uncertainty; it would be equally fallacious to assert without qualification that God's presence causes the brain to be stimulated in a certain way. Baggini would perhaps put himself on even safer ground by saying "perhaps that is simply a mechanism by which the real God makes himself known", since we cannot assume that God would restrict himself to revelation by temporal and parietal lobe disturbance.

Also, the Economist has an unsigned―so, I really don't know who the reviewer is―review of Dennett's book that makes it sound quite different than the Kirsch review does. Moreover, it has a reasonable, if not exciting, title!

Source: "Let's Cool Down and Look at this Rationally", The Economist, 2/9/2006

Fallacy: Genetic Fallacy

February 3rd, 2006 (Permalink)

Blurb Watch: Annapolis

Pity the poor adwriter stuck with a critically panned movie, such as the new movie "Annapolis", whose Metacritic rating is 37 out of 100―meaning "Generally Unfavorable Reviews"―and whose Tomatometer rating is a "Rotten" 10%. However, with some creative editing, gratuitous capitalization, and exclamation point, even an unfavorable review can sound like a rave:

Blurb Context
Christy Lemire, Associated Press
The location is the U.S. Naval Academy, but you've been to "Annapolis" before, several times over. This rousing, crowd-pleasing drama crams in every underdog cliche, as well as every boxing-movie cliche and military-movie cliche. Surely one of these alone would have been sufficient.


Fallacy: Quoting Out of Context

February 2nd, 2006 (Permalink)

STATS on Sex

Maia Szalavitz of the Statistical Assessment Service has a cogent criticism of a New York Times article which reported on research into the connection between media portrayals of sex and teenage sexual behavior. While the article repeatedly mentions that almost nothing is known about the effects of sex in the media on teenagers, the language of the article frequently suggests otherwise. For instance, the results of two telephone surveys are described as follows:

The research indicated that adolescents who watched shows with sexual content tended to overestimate the frequency of certain sexual behaviors and to have more permissive attitudes toward premarital sex.

This wording suggests that watching such shows leads to the overestimates and permissive attitudes. However, the sentence could have just as accurately been worded as follows:

The research indicated that adolescents who overestimate the frequency of certain sexual behaviors and have more permissive attitudes toward premarital sex tended to watch shows with sexual content.

All that a telephone survey can show is a positive correlation between the type of shows watched and permissive attitudes, not the causal relation between them. Though it's plausible that watching a lot of sex on TV might lead to permissive attitudes, it's just as plausible that permissive attitudes may lead to watching sex on TV.


Fallacy: Cum Hoc, Ergo Propter Hoc

Answer to the Puzzle: A cat. The numbers are in binary notation.

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