Posted on 12/30/2003 11:34:11 AM PST by general_re
It is obvious that any reasoning that relies on treating as the cause of some thing or event what is not really its cause must be seriously mistaken. But often we are tempted to suppose, or led to suppose, that we understand some specific cause-and-effect relation when in fact we do not. The nature of the connection between cause and effect, and how we determine whether such a connection is present or absent, are central problems of inductive logic and scientific method. These problems are discussed in detail in Part Four of this book. Presuming the reality of a causal connection that does not really exist is, in any event, a common mistake; in Latin the mistake is called the fallacy of non causa pro causa; we call it simply the fallacy of false cause.
It sometimes happens that we presume that one event is caused by another because it follows that other closely in time. We know, of course, that mere temporal succession does not establish a causal connection, but it is easy to be fooled. If an aggressive move in foreign policy is followed by a distantly related international event for which we had been aiming, some may mistakenly conclude that the aggressive policy was the cause of that event. In primitive science such mistakes were common; we now reject as absurd the claim that beating drums is the cause of the sun's reappearance after an eclipse, despite the undeniable evidence that every time drums have been beaten during an eclipse the sun subsequently did reappear.
Mistakes in reasoning of this kind remain widespread: Unusual weather conditions are blamed on some unrelated celestial phenomenon that happened to precede them; an infection really caused by a virus is thought to be caused by a chill wind or wet feet, and so on. This variety of false cause is called the fallacy of post hoc ergo propter hoc ("after the thing, therefore because of the thing"); an example of it appeared in a recent letter to The New York Times, in which the correspondent wrote:
The death penalty in the United States has given us the highest crime rate and greatest number of prisoners per 100,000 population in the industrialized world.
Post hoc ergo propter hoc is an easy fallacy to detect when it is blatant, but even the best of scientists and statesmen are on occasion misled.
To beg the question is to assume the truth of what one seeks to prove, in the effort to prove it. That would seem to be a silly mistake, evident to all — but how silly or obvious the mistake is depends largely on the way in which the premisses of the argument are formulated. Their wording often obscures the fact that buried within one of the premisses assumed lies the conclusion itself. This fallacy is illustrated by the following argument, reported long ago by the logician Richard Whately: "To allow every man unbounded freedom of speech must always be, on the whole, advantageous to the state; for it is highly conducive to the interests of the community that each individual should enjoy a liberty, perfectly unlimited, of expressing his sentiments."
Sometimes we fall into this mistake when, in the effort to establish our conclusion, we cast about in search of premisses that will do the trick. Of course the conclusion itself, disguised in other language, certainly will do the trick! Most fallacies, we noted earlier, can be viewed in some light as fallacies of relevance — but the petitio principii cannot. The premisses of the argument, in this case, are not irrelevant; they certainly do prove the conclusion — but they do so trivially. A petitio principii is always technically valid — but always worthless, as well.
This is another of those mistakes that often go unrecognized by those who commit them. The presumption buried in the premisses may be obscured by confusing or unrecognized synonyms, or by a chain of intervening argument. Every petitio is a circular argument, but the circle that has been constructed may — if it is large or fuzzy — go quite undetected.
Powerful minds sometimes are snared by this fallacy, as is illustrated by a highly controversial issue in the history of philosophy. Logicians have long sought to establish the reliability of inductive procedures by establishing the truth of what is called the "principle of induction." This is the principle that the laws of nature will operate tomorrow as they operate today, that in basic ways nature is essentially uniform, and that therefore we may rely on past experience to guide our conduct in the future. "That the future will be essentially like the past" is the claim at issue, but this claim, never doubted in ordinary life, turns out to be very difficult to prove. Some thinkers have claimed that they could prove it by showing that, when we have in the past relied on the inductive principle, we have always found that this method has helped us to achieve our objectives. They ask, "Why conclude that the future will be like the past?" and answer, "Because it always has been like the past."
But as David Hume pointed out, this common argument is a petitio, it begs the question. For the point at issue is whether nature will continue to behave regularly; that it has done so in the past cannot serve as proof that it will do so in the future — unless one assumes the very principle that is here in question: that the future will be like the past. And so Hume, granting that in the past the future has been like the past, asked the telling question with which philosophers still tussle: How can we know that future futures will be like past futures? They may be so, of course, but we may not assume that they will be for the sake of proving that they will.
The example I still remember from a long-ago logic course is this:
1. If it rains, the streets will be wet.
2. The streets are wet.
3. Therefore it must have rained.
Your're probably right; if recollection serves, the "No True Scotsman" is actually a special case -- a an example of two types of fallacy being committed at the same time. I think comes down to "equivocation" and "begging the question" at the same time. The equivocation involves narrowing the definition [of a "true Scotsman"] as needed to avoid refutation, and the begging of the question is used to justify it.
Moving along, I've noticed that your wonderful series on logical fallacies isn't generating the sort of enthusiastic response it deserves. In order to rectify this, I propose the following: for each fallacy type, participants should provide actual examples culled from the archives of FR, as originally posted by, ummmmm...... let's just say "FReepers-no-longer-in-residence." THe Freeper posting the best example of a given fallacy will win a prize, say a one week stay on a deserted island with those hilarious and fun-loving former Freepers "ALS" and "Gore3000." The second place prize is a TWO weeks on the island with them......
That should liven things up a bit....
P1: If it rains, the streets will be wet.
P2: It did not rain.
C1: Therefore, the streets are not wet.
or:
If p, then q.
~p.
Therefore, ~q.
1. All communists are atheists.This, in various clumsy versions, was used by virtually all the now-gone creationists. Not only is the structure of the argument fallacious, but the premise is false.
2. Darwin was an atheist.
3. Ergo ...
Kewl - you keep giving me opportunities to introduce new stuff ;)
As you say, the structure of such an argument is incorrect, which makes the basic logical error in this argument a formal error, as opposed to the informal errors that this series has been devoted to thus far. Essentially, the argument is this:
P1: All communists are atheists.
P2: Darwin was an atheist. (effectively equivalent to the universal affirmative proposition that "All men named Charles Darwin are atheists", or "All 'Darwins' are atheists")
C1: Therefore, Darwin was a communist.
Or some such.
A term in a syllogism is said to be "distributed" when the proposition refers to all members of the class designated by that term. And in a standard syllogism, the middle term (in this case, "atheists") must be distributed in at least one of the premises. But the middle term is undistributed in both premises - no claims about all the members of the class "atheists" are advanced - and hence the syllogism is invalid on its face. Not surprisingly, this formal error is known as the fallacy of the undistributed middle. The fact that the second premise is known to be false is merely the icing on the fallacy cake, so to speak.
P1: All men named Charles Darwin are atheists.
P2: All atheists are communists.
C1: Therefore, all men named Charles Darwin are communists.
Notice that the middle term, "atheists", is now properly distributed, by virtue of the fact that the second premise refers to all members of the class. However, while the logic is now valid, it is still unsound, insofar as the premises are known to be false.
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