Diagnostic Test - Arguments - Common Fallacies - Review

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COMMON FALLACIES

Contradiction
A Contradiction is committed when two opposing statements are simultaneously asserted. For example, saying "it is raining and it is not raining" is a contradiction. Typically, however, the arguer obscures the contradiction to the point that the argument can be quite compelling. Take, for instance, the following argument:

"We cannot know anything, because we intuitively realize that our thoughts are unreliable."

This argument has an air of reasonableness to it. But "intuitively realize" means "to know." Thus the arguer is in essence saying that we know that we don't know anything. This is self-contradictory.

Equivocation
Equivocation is the use of a word in more than one sense during an argument. This technique is often used by politicians to leave themselves an "out." If someone objects to a particular statement, the politician can simply claim the other meaning.

Example:
Individual rights must be championed by the government. It is right for one to believe in God. So government should promote the belief in God.

In this argument, right is used ambiguously. In the phrase "individual rights" it is used in the sense of a privilege, whereas in the second sentence right is used to mean proper or moral. The questionable conclusion is possible only if the arguer is allowed to play with the meaning of the critical word right.

Circular Reasoning
Circular reasoning involves assuming as a premise that which you are trying to prove. Intuitively, it may seem that no one would fall for such an argument. However, the conclusion may appear to state something additional, or the argument may be so long that the reader may forget that the conclusion was stated as a premise.

Example:
The death penalty is appropriate for traitors because it is right to execute those who betray their own country and thereby risk the lives of millions.

This argument is circular because "right" means essentially the same thing as "appropriate." In effect, the writer is saying that the death penalty is appropriate because it is appropriate.

Shifting The Burden of Proof
It is incumbent on the writer to provide evidence or support for her position. To imply that a position is true merely because no one has disproved it is to shift the burden of proof to others.

Example:
Since no one has been able to prove God's existence, there must not be a God.

There are two major weaknesses in this argument. First, the fact that God's existence has yet to be proven does not preclude any future proof of existence. Second, if there is a God, one would expect that his existence is independent of any proof by man.

Unwarranted Assumptions
The fallacy of unwarranted assumption is committed when the conclusion of an argument is based on a premise (implicit or explicit) that is false or unwarranted. An assumption is unwarranted when it is false--these premises are usually suppressed or vaguely written. An assumption is also unwarranted when it is true but does not apply in the given context--these premises are usually explicit.

Example: (False Dichotomy)
Either restrictions must be placed on freedom of speech or certain subversive elements in society will use it to destroy this country. Since to allow the latter to occur is unconscionable, we must restrict freedom of speech.

The conclusion above is unsound because (A) subversives do not in fact want to destroy the country (B) the author places too much importance on the freedom of speech (C) the author fails to consider an accommodation between the two alternatives (D) the meaning of "freedom of speech" has not been defined (E) subversives are a true threat to our way of life

The arguer offers two options: either restrict freedom of speech, or lose the country. He hopes the reader will assume that these are the only options available. This is unwarranted. He does not state how the so-called "subversive elements" would destroy the country, nor for that matter, why they would want to destroy it. There may be a third option that the author did not mention; namely, that society may be able to tolerate the "subversives" and it may even be improved by the diversity of opinion they offer. The answer is (C).

Appeal to Authority
To appeal to authority is to cite an expert's opinion as support for one's own opinion. This method of thought is not necessarily fallacious. Clearly, the reasonableness of the argument depends on the "expertise" of the person being cited and whether she is an expert in a field relevant to the argument. Appealing to a doctor's authority on a medical issue, for example, would be reasonable; but if the issue is about dermatology and the doctor is an orthopedist, then the argument would be questionable.

Personal Attack
In a personal attack (ad hominem), a person's character is challenged instead of her opinions.

Example:
Politician: How can we trust my opponent to be true to the voters? He isn't true to his wife!

This argument is weak because it attacks the opponent's character, not his positions. Some people may consider fidelity a prerequisite for public office. History, however, shows no correlation between fidelity and great political leadership.