3b. Analysis of Argument: Finding Errors

The Usual Suspects: Common Logical Fallacies

We have identified seven logical errors that appear commonly in the essay questions. When writing your essay argument you should explicitly identify the logical flaw. These flaws also tend to occur in the critical reasoning section of the Verbal Section, so your preparation here will benefit you when taking the Verbal section.

The E-rater will look for how well you express that you have identified the logical reasoning flaws. When you find an error, specifically identify it in the essay "this is a biased-sample fallacy." The E-rater will detect that you have identified the argument's flaw and will favor your essay.

1. Circular Reasoning

     Here, an unsubstantiated assertion is used to justify another unsubstantiated assertion, which is, or at least could be, used to justify the first statement. For instance, Joe and Fred show up at an exclusive club. When asked if they are members, Joe says "I'll vouch for Fred." When Joe is asked for evidence that he's a member, Fred says, "I'll vouch for him."

2. The Biased-Sample Fallacy

     The Fallacy of the Biased Sample is committed whenever the data for a statistical inference are drawn from a sample that is not representative of the population under consideration. The data drawn and used to make a generalization is drawn from a group that does not represent the whole.

Here is an argument that commits the fallacy of the biased sample:

ln a recent survey conducted by Wall Street Weekly, 80% of the respondents indicated their strong disapproval of increased capital gains taxes. This survey clearly shows that increased capital gains taxes will meet with strong opposition from the electorate.

     The data for the inference in this argument are drawn from a sample that is not representative of the entire electorate. Since the survey was conducted of people who invest, not all members of the electorate have an equal chance of being included in the sample. Moreover, persons who read about investing are more likely to have an opinion on the topic of taxes on investment different from the population at large.


3. The Insufficient Sample Fallacy

     The Fallacy of the Insufficient Sample is committed whenever an inadequate sample is used to justify the conclusion drawn.

Here's an argument that commits the fallacy of the insufficient sample:

I have worked with 3 people from New York City and found them to be obnoxious, pushy and rude. It is obvious that people from New York City have a bad attitude.

The data for the inference in this argument are insufficient to support the conclusion. Three observations of people are not sufficient to support a conclusion about 10 million.

4. Ad hominen

     One of the most often-employed fallacies, ad hominen means "to the man" and indicates an attack that is made upon a person rather than upon the statements that person has made. An example is: "Don't listen to my opponent, he's a homosexual."

 

5. The Fallacy of Faulty Analogy       

     Reasoning by analogy functions by comparing two similar things. Because they are alike in various ways, the fallacy is that it is likely they will share another trait as well. Faulty Analogy arguments draw similarities between the things compared that are not relevant to the characteristic being inferred in the conclusion.

Here's an example of a Faulty Analogy fallacy:

Ted and Jim excel at both football and basketball. Since Ted is also a track star, it is likely that Jim also excels at track.

In this example, numerous similarities between Ted and Jim are taken as the basis for the inference that they share additional traits.

 

6. Straw Man

     Here the speaker attributes an argument to an opponent that does not represent the opponent's true position. For instance, a political candidate might charge that his opponent "wants to let all prisoners go free," when in fact his opponent simply favors a highly limited furlough system. The person is portrayed as someone that they are not.

 

7. The "After This, Therefore, Because of This" Fallacy (Post hoc ergo propter hoc)

     This is a "false cause" fallacy in which something is associated with something else because of mere proximity of time. One often encounters - in news stories- people assuming that because one thing happened after another, the first caused it, as with "I touched a toad, I have a wart, the toad caused the wart." The error in arguments that commit this fallacy is that their conclusions are causal claims that are not sufficiently substantiated by the evidence.

Here are two examples of the After This, Therefore Because of This Fallacy:

Ten minutes after walking into the auditorium, I began to feel sick to
my stomach. There must have been something in the air in that building that caused my nausea.

The stock market declined shortly after the election of the president,
thus indicating the lack of confidence the business community has in the new administration.

     In the first example, a causal connection is posited between two events simply on the basis of one occurring before the other. Without further evidence to support it, the causal claim based on the correlation is premature.

     The second example is typical of modern news reporting. The only evidence offered in this argument to support the implicit causal claim that the decline in the stock market was caused by the election of the president is the fact that election preceded the decline. While this may have been a causal factor in the decline of the stock market, to argue that it is the cause without additional information and auxiliary hypotheses that make a causal connection plausible is to commit the After This, Therefore, Because of This Fallacy.

8. The Either-or Thinking

      This is the so-called black-or-white fallacy. Essentially, it says "Either you believe what I'm saying or you must believe exactly the opposite." Here is an example of the black-or-white fallacy:

Since you don't believe that the earth is teetering on the edge of destruction, you must believe that pollution and other adverse effects that man has on the environment are of no concern whatsoever.

The argument above assumes that there are only two possible alternatives open to us. There is no room for a middle ground.

9. The "All Things are Equal" Fallacy

     This fallacy is committed when it is assumed, without justification, that background conditions have remained the same at different times/locations. In most instances, this is an unwarranted assumption for the simple reason that things rarely remain the same over extended periods of time, and things rarely remain the same from place to place.

The last Democrat winner of the New Hampshire primary won the general election. This year, the winner of the New Hampshire primary will win the general election.

     The assumption operative in this argument is that nothing has changed since the last primary. No evidence or justification is offered for this assumption.

 

10. The Fallacy of Equivocation

    The Fallacy of Equivocation occurs when a word or phrase that has more than one meaning is employed in different meanings throughout the argument.

"Every society is, of course, repressive to some extent - as Sigmund Freud pointed out, repression is the price we pay for civilization." (John P. Roche- political columnist)

In this example, the word repression is used in two completely different contexts. "Repression" in Freud's mind meant rerstricting sexual and psychological desires. "Repression" in the second context does not mean respression of individual desires, but government restriction of individual liberties, such as that in a totalitarian state.

11. Non Sequitor

     This means "does not follow," which is short for: the conclusion does not follow from the premise. To say, "The house is white; therefore it must be big" is an example. It may be a big house but there is no intrinsic connection with its being white.

12. Argument ad populum

     A group of kindergartners are studying a frog, trying to determine its sex. "I wonder if it's a boy frog or a girl frog," says one student. "I know how we can tell!" pipes up another. "All right, how?" asks the teacher, resigned to the worst. Beams the child: "We can vote."

     This is argumentum ad populum, the belief that truth can be determined by more or less putting it to a vote. Democracy is a very nice thing, but it doesn't determine truth. Polls are good for telling you what people think, not whether those thoughts are correct.

Common Student Errors We've graded essays from thousands of students and we see recurring errors time and time again. The most common error on the Analysis of Argument essay is "Splitting Hairs." Splitting Hairs refers to trying to dissect errors that do no fall into the categories listed here. Remember that all questions have SERIOUS errors. The danger is that you could get distracted on a minor issue and miss the serious errors that the E-rater and the grader want to see.

This logic professor's site contains excellent examples.

>>continue to Analysis of Argument: Template (page 4 of 5 of chapter 5)