Linguistics update

Logical Fallacies

Logical fallacies are errors that occur in arguments. In logic, an argument is the giving of reasons (called premises) to support some claim (called the conclusion). There are many ways to classify logical fallacies. I prefer listing the conditions for a good or cogent argument and then classifying logical fallacies according to the failure to meet these conditions.

Every argument makes some assumptions. A cogent argument makes only warranted assumptions, i.e., its assumptions are not questionable or false. So, fallacies of assumption make up one type of logical fallacy. One of the most common fallacies of assumption is called begging the question. Here the arguer assumes what he should be proving. Most arguments for psi commit this fallacy. For example, many believers in psi point to the ganzfeld experiments as proof of paranormal activity. They note that a .25 success rate is predicted by chance but Honorton had some success rates of .34. One defender of psi claims that the odds of getting 34% correct in these experiments was a million billion to one. That may be true but one is begging the question to ascribe the amazing success rate to paranormal powers. It could be evidence of psychic activity but there might be some other explanation as well. The amazing statistic doesn't prove what caused it. The fact that the experiment is trying to find proof of psi isn't relevant. If someone else did the same experiment but claimed to be trying to find proof that angels, dark matter, or aliens were communicating directly to some minds, that would not be relevant to what was actually the cause of the amazing statistic. The experimenters are simply assuming that any amazing stat they get is due to something paranormal.

Another common--and fatal--fallacy of assumption is the false dilemma, whereby one restricts consideration of reasonable alternatives.

Not all fallacies of assumption are fatal. Some cogent arguments might make one or two questionable or false assumptions, but still have enough good evidence to support their conclusions. Some, like the gambler's fallacy, are fatal, however.

Another quality of a cogent argument is that the premises are relevant to supporting their conclusions. Providing irrelevant reasons for your conclusion need not be fatal, either, provided you have sufficient relevant evidence to support your conclusion. However, if all the reasons you give to support of your conclusion are irrelevant then your reasoning is said to be a non sequitur. The divine fallacy is a type of non sequitur.

One of the more common fallacies of relevance is the ad hominem, an attack on the one making the argument rather than an attack on the argument. One of the most frequent types of ad hominem attack is to attack the person's motives rather than his evidence. For example, when an opponent refuses to agree with some point that is essential to your argument, you call him an "antitheist" or "obtuse."

Other examples of irrelevant reasoning are the sunk-cost fallacy and the argument to ignorance.

A third quality of a cogent argument is sometimes called the completeness requirement: A cogent argument should not omit relevant evidence. Selective thinking is the basis for most beliefs in the psychic powers of so-called mind readers and mediums. It is also the basis for many, if not most, occult and pseudoscientific beliefs. Selective thinking is essential to the arguments of defenders of untested and unproven remedies. Suppressing or omitting relevant evidence is obviously not fatal to the persuasiveness of an argument, but it is fatal to its cogency. The regressive fallacy is an example of a fallacy of omission. The false dilemma is also a fallacy of omission.

A fourth quality of a cogent argument is fairness. A cogent argument doesn't distort evidence nor does it exaggerate or undervalue the strength of specific data. The straw man fallacy violates the principle of fairness.

A fifth quality of cogent reasoning is clarity. Some fallacies are due to ambiguity, such as the fallacy of equivocation: shifting the meaning of a key expression in an argument. For example, the following argument uses 'accident' first in the sense of 'not created' and then in the sense of 'chance event.'

Since you don't believe you were created by God then you must believe you are just an accident. Therefore, all your thoughts and actions are accidents, including your disbelief in God.

Finally, a cogent argument provides a sufficient quantity of evidence to support its conclusion. Failure to provide sufficient evidence is to commit the fallacy of hasty conclusion. One type of hasty conclusion that occurs quite frequently in the production of superstitious beliefs and beliefs in the paranormal is the post hoc fallacy.

Some fallacies may be classified in more than one way, e.g., the pragmatic fallacy, which at times seems to be due to vagueness and at times due to insufficient evidence.

Fallacy: Loaded Questions and Complex Claims

1. Your father: Did you enjoy spoiling the dinner for everyone else?
2. Your mother: Well, I hope you enjoyed making a fool of me in front of all my friends.
3. Your boss: Can you begin to appreciate this wonderful opportunity I'm making available to you?
4. Your significant other: Have you finally stopped flirting with Dana?
5. Your critical thinking instructor: Aren't you ashamed about how little effort you've made in this class?

Complex claims and questions--that is, ones that combine two or more questionable terms--present a special problem, if they are constructed in such a way that agreement or disagreement with one term seems to imply agreement with the second. In the first example above, the reply, "No I didn't," can be taken to mean, "I didn't enjoy it, but I did spoil the dinner," when it may actually be intended as a denial that the dinner was spoiled. Questions like the one in the first example are usually called loaded questions, because, like loaded dice, they seem to produce a predictable outcome: as long as the response to a complex question or claim is simple, usually just "yes" or "no," then the person responding seems to be assenting to something he or she normally would not. The impulse to give a simple response is strongest in reply to certain questions, and so loaded questions are the more common form of this fallacy. But complex claims can have the same effect, as in the second example above. You might protest, "Mom! No, I certainly didn't," but that would only sound as though you made a fool out of her in front of her friends, and didn't even enjoy it! The relationship between the speaker and the responder, and the situation in which the question is asked, greatly affects the "success" of a loaded question. But just as important is that the question must be constructed in a way that clearly prompts a "yes" or "no" answer, and that the least agreeable element of complexity be buried in the sentence. Consider the third example. Since you would want to appear properly appreciative to your boss, you might answer this question affirmatively before considering whether such a response would commit you to agreeing that the opportunity is, in fact, wonderful, and that your boss has, in fact, made it available to you. In the same way, the fourth example seems to demand a quick denial, but saying simply "No," suggests not only that you have been flirting with Dana, but that you are continuing to do so. But would you ever answer "yes"? Finally, the fifth example shows that critical thinking instructors are not above fallaciously promoting a little guilt to get students to study harder. Answering the question as asked, with "yes" or "no," would only accept or deny the claim that you are ashamed, but in either case it would also seem to acquiesce in the notion that you haven't made much of an effort. The solution to this fallacy is simple: A complex question or claim requires a complex response. Do not allow the question to dictate your answer. Instead, without prefacing your response with "yes" or "no," indicate whether you agree or disagree with the characterization implied by each term in succession: "Dad, I didn't mean to spoil the dinner, I don't think I did, and I certainly wouldn't have enjoyed it if I thought I had"; "Mom, I hope I didn't make a fool of you, in front of your friends or at any other time, and I certainly wouldn't have enjoyed it had I done anything that might make you think that"; "Boss, I do appreciate the opportunity, but I just don't think it's very wonderful"; "Honey, I wasn't flirting with Dana, so I can't stop something I wasn't doing"; "Professor, aren't you ashamed of yourself, fallaciously attacking my self-esteem with an intentionally loaded question?" Sometimes, answering a loaded question with another loaded question is the best reply.

http://www.sjsu.edu/depts/itl/graphics/adhom/loaded.html

Replication of Scientific Studies

A student who did very well in my Logic and Critical Reasoning course sent the following news item along with the suggestion that I might need to revise my thinking about lunar effects. I replied that I might need to emphasize more strongly what I teach: Look for what is not mentioned in the study, not just at what is mentioned. And don't forget how important replication of a study is.

Aug 11, 2003. (Bloomberg) -- Car accidents occur 14 percent more often on average during a full moon than a new moon, according to a study of 3 million car policies by the U.K.'s Churchill Insurance Group Plc.

The data show a rise in all types of accidents, involving single vehicles or multiple cars, the company said in an e-mailed press release. The next full moon will be tomorrow night.

``We know that the moon is a strong source of energy, as it affects the tides and weather patterns, but were surprised by this bizarre trend,'' Craig Staniland, head of car insurance at Churchill, said in the release.

The company, which Royal Bank of Scotland Group Plc agreed to buy from Credit Suisse Group in June, speculated that eastern philosophy's concepts of yin and yang may explain the accident rate. It cited a feng shui expert, Simon Brown, saying that the full moon radiates more of the sun's yang energy onto earth, making people more aggressive and impatient.

The insurer said it won't change its underwriting criteria to take the full moon into account, the company said.

In addition to yin and yang, there might be other explanations for this data, but before searching for explanations one should make sure there is something that needs to be explained. The study seems to claim that there are 14% more accidents on nights when there is a full moon than on nights when there is a new moon. (When the moon is full, if the weather is clear, it will generally be very bright. When the moon is new, even if the weather is clear, the moon will hardly be visible.)* The results of a single study may be suggestive but they are not usually considered conclusive. This study may have been well-designed but we are not told anything about how it was conducted or how it was designed, so we can't be sure. The Churchill Insurance Group may have a flawless study, but note that they didn't take the results seriously enough to alter their underwriting criteria. Why not? I don't know. What I would like to know is how was the study done?

The press release mentions a study of 3 million car policies but that's a bit vague. Did they analyze 3 million policies and separate those who made accident claims from those who didn't? Then, did they find that claims that involved accidents that happened at night when there was a full moon occurred 14% more frequently than claims that involved accidents that happened at night when there was a new moon? Did they control for weather? That is, did they review their data to make sure that there were about the same number of stormy nights on both full and new moon nights? Otherwise, they might just be measuring an effect of bad weather, not moon phases.

How many accidents are we talking about? Without knowing the numbers we can't determine whether this study had a sufficient number of cases to analyze. But even if it had many thousands of cases, we don't know over how long a period of time this study was conducted. If it analyzed data over a very long period of time, that would be more impressive than if it analyzed data over a very short period of time. Why? Over a short period of time they are more likely to get skewed results. For example, maybe the period they evaluated had two full moons in 30 days and both occurred on Saturdays. With smaller numbers it becomes more important to control for factors like the weather or weekends.

We need to know exactly how many accidents were involved in the study, the beginning date and end date of the data collection, the exact number of nights involved, and the exact number of full and new moons during the study. We should also be assured that only accidents that occurred after the rising and before the setting of the full moon were included in the study. If the accidents happened during the day or before the full moon was present, the likelihood that the moon had anything to do with diminishes significantly.

Finally, even if the study was based on a sufficient number of cases over an adequate period of time and included only data it should include (and didn't include data it shouldn't include), and even if the data were analyzed properly by professional statisticians, we should still wait until it is replicated before worrying about finding an explanation for the 14% statistic. A single study with statistically impressive results should not be taken as sufficient to base any important decisions on.

Now, trying to prove the statistic is due to yin and yang is another matter altogether. I have no idea how anyone could construct a scientific study to test that hypothesis.

But we can at least correct one misconception put forth in this press release: the moon is not a strong source of gravitational energy on earthlings. George Abell claims that a mosquito would exert more gravitational pull on your arm than the moon would. Ivan Kelly put it this way: "A mother holding her child "will exert 12 million times as much tidal force on her child as the moon."*

Why would anyone cite this study favorably? Confirmation bias. If you already believe in lunar effects, this study confirms your belief. You will be less likely to be critical of it than if it goes against your beliefs. Also, the suburban myth that the moon is a strong source of energy continues to be reported in the media, giving many people the impression that it must be true.

http://www.blogger.com/post-create.g?blogID=4178106086788702272

divine fallacy (argument from incredulity)

The divine fallacy, or the argument from incredulity, is a species of non sequitur reasoning which goes something like this: I can't figure this out, so God must have done it. Or, This is amazing; therefore, God did it. Or, I can't think of any other explanation; therefore, God did it. Or, this is just too weird; so, God is behind it.

This fallacy is also a variation of the alien fallacy: I can't figure this out, so aliens must have done it. Or, This is amazing; therefore, aliens did it. Or, I can't think of any other explanation; therefore, aliens did it. Or, this is just too weird; so, aliens are behind it.

Another variation of the fallacy goes something like this: I can't figure this out, so paranormal forces must have done it. Or, This is amazing; therefore, paranormal forces did it. Or, I can't think of any other explanation; therefore, paranormal forces did it. Or, this is just too weird; so, paranormal forces are behind it.

http://www.skepdic.com/dvinefal.html