Since 07-17-99
FALLACIES IN GENERAL A fallacy is a certain kind of defect in an argument. One way that an argument can be defective is by having one or more false premises. Another way is by containing a fallacy. Both deductive and inductive arguments may be affected by fallacies. If either kind contains a fallacy, it is either unsound or uncogent, depending on the kind of argument. |
2. Hasty Generalization (Converse
Accident) Hasty generation is a fallacy that affects inductive generalizations. An inductive generalization is an argument that draws a conclusion about all members of a group from evidence that pertains to a selected sample. The fallacy occurs when there is a likelihood that the sample is not representative of the group. Such likelihood may arise if the sample is either too small or not randomly selected. Here are two examples:
In these arguments a conclusion about a whole group is drawn from premises that mention only two instances. Because such small, atypical samples are not sufficient to support a general conclusion, each argument commits a hasty generalization. The second example indicates how hasty generalization plays a role in racial (and religious) prejudice |
The mere fact
that a sample may be small, however, does not necessarily entail that it is atypical.
Sometimes other factors intervene that cause the argument to be strong in spite of
the fact that the sample may be small. Examples:
Neither of these arguments commits the fallacy of hasty generalization because in neither case is there any likelihood that the sample is atypical of the group. In the first argument the fact that the mice died in only two minutes suggests the existence of a causal connection between eating substance Z and death.; If there is such a connection, it would hold for other mice as well. In the second example the fact that the taste of beer typically remains constant from bottle to bottle causes the argument to be strong, even though only three bottles were sampled. |
| Hasty generalization is otherwise called "converse accident" because it proceeds in a direction opposite to that of accident. Whereas accident moves from the particular to the general. The premises cite some characteristic affecting one or more atypical instances of a certain class, and the conclusion then applies that characteristic to all members of the class. |
**By Irving M. Copi. Introduction to Logic In seeking to understand and characterize all cases of a certain kind, one can usually pay attention to only some of them. But those examined should be typical rather than atypical. If one considers only unusual or atypical cases and generalizes to a rule that fits them alone, the fallacy committed is the Fallacy of Converse Accident. For example, observing the value of opiates when administered by a physician to alleviate the suffering of those who are seriously ill, one may be led to propose that narcotics be made available to everyone. Or considering the effect of alcohol only on those who indulge in it to excess, one may conclude that all liquor is harmful and urge that its sale and use should be forbidden by law. Such reasoning is faulty, and it illustrates the Fallacy of Converse Accident. |
3. Begging the Question Begging the question occurs when an arguer uses some form of phraseology that tends to conceal the questionably true character of a key premise. If the reader or listener is deceived into thinking that the key premise is true, he or she will accept the argument as sound, when in fact it may not be. Two requirements must be met for this fallacy to occur:
The kind of phraseology used varies from argument to argument, but it often involves using the conclusion to support the questionable premise. One way of accomplishing this is to phrase the argument so that the premise and conclusion say the same thing in two slightly different ways. Example:
To say that capital punishment is "justified" means the same thing as to say that it is "legitimate and appropriate." Because premise and conclusion mean the same thing, it is obvious that if the premise is true, the conclusion is also true; so the argument is valid. The only question that remains is whether the premise is true. When read apart from the context of the argument, the premise is questionable, at best. But when it is preceded by the conclusion, as it is here, the alleged truth is strengthened. This strengthening is caused by the psychological illusion that results from saying the same thing in two slightly different ways. When a single proposition is repeated in two or more ways without the repetition becoming obvious, the suggested truth of the proposition is reinforced.
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Another form of begging the question affects chains of arguments. Example:
In this chain of arguments the final conclusion is stated first. The truth of this conclusion depends on each link in the chain, and ultimately on the first premise (stated last), which asserts the same thing as the final conclusion (stated first). This example illustrates why begging the question is frequently called circular reasoning. The artifice used in arguments such as this depends on the fact that several statements intervene between the final conclusion and the first premise. The reader or listener tends to get lost in the maze of arguments, and since every statement appears to be supported by some other statement, he or she can be fooled into thinking that the final conclusion is necessarily true. What the reader or listener may fail to recognize is that the truth of the final conclusion is really reported only by itself, and therefore by nothing at all.
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A third
form of begging the question occurs when a questionably true premise, which is needed to
make the argument valid, is completely ignored. Example:
The questionable premise that is ignored is, "Abortion is a form of murder." The argument begs the question, "How do you know that abortion is a form of murder?" The premise that is stated, of course, is indisputably true, and the phrase "This being the case" makes it appear that the stated premise is all that is needed. If the reader or listener concentrates on the truth of the stated premise and overlooks the fact that a highly questionable premise is needed to complete the argument, he or she is liable to accept the argument as immediately sound. An essential characteristic of begging the question is that some form of phraseology be used that tends to conceal the questionably true character of a key premise. If this premise is obviously true, then no such concealment is relevant, and the fallacy cannot occur. Consider the following argument:
This argument is valid and the premise is true. The argument is therefore sound and contains no fallacies. Many logic texts consider arguments such as this to be instances of begging the question, but according to the position taken here, these views are mistaken. Obviously, the argument is trivial, but mere triviality is not a fallacy Here is another example:
This argument is valid but has a false premise. Accordingly, the argument is unsound, but it commits no fallacy. Although the premise is false, there is no phraseology that tends to hide this fact, and so begging the question is not committed. Literally, petitio principii means "postulation of the beginning." In other words, what argument sets out to do in the beginning is postulated instead of proven. "Begging the question" means the same thing. The argument begs the question at issue; it asks that the statement to be proved be granted beforehand.
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4. Suppressed Evidence The fallacy of suppressed evidence is committed when an arguer ignores evidence that would tend to undermine the premises of an otherwise good argument, causing it to be unsound or uncogent. Suppressed evidence is a fallacy of presumption and is closely related to begging the question. As such, its occurrence does not affect the relationship between premises and conclusion but rather the alleged truth of the premises. The fallacy consists in passing off what are at best half-truths as if they were the whole truth, thus making what is actually a defective argument appear to be good. The fallacy is especially common among arguers who have a vested interest in the situation to which the argument pertains. Another form of suppressed evidence is committed by arguers who quote passages out of context from sources such as the Bible, the Constitution, and the Bill of Rights to support a conclusion that the passage was not intended to support.
To detect the fallacy of suppressed evidence, the reader or listener must be cautious that the arguer is not ignoring evidence that has a bearing on the premises. This, in turn, requires a general knowledge of the topic to which the argument pertains and a familiarity with the devices used by unscrupulous individuals to pass off half-truths as the whole truth.
(will be continued) |
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07-17-99
Since 07-17-99