Part 20 (2/2)
I. This principle is in accordance with the principles of the Democratic party, since
A. The leader of the Democratic party believes in it, for
1. As the leader of the party, he naturally believes in Democratic principles.
II. AMBIGOUS TERMS. (EQUIVOCATION; CONFUSION OF TERMS.)
The fallacy of ambiguous terms consists of using the same term in two distinct senses in the same argument. Thus if one were to argue that ”no designing person ought to be trusted; engravers are by profession designers; therefore they ought not to be trusted,” it is quite apparent that the term ”design” means totally different things in the two premises. The same fallacy occurs in the argument, ”Since the American people believe in a republican form of government, they should vote the Republican ticket.” Again:--
”Interference with another man's business is illegal;
”Underselling interferes with another man's business;
”Therefore underselling is illegal.”
J. S. Mill in his _System of Logic_ discusses the fallacy of ambiguous terms with great care. In part he says:--
The mercantile public are frequently led into this fallacy by the phrase ”scarcity of money.” In the language of commerce, ”money” has two meanings: _currency,_ or the circulating medium; and _capital seeking investment,_ especially investment on loan. In this last sense, the word is used when the ”money market” is spoken of, and when the ”value of money” is said to be high or low, the rate of interest being meant. The consequence of this ambiguity is, that as soon as scarcity of money in the latter of these senses begins to be felt,--as soon as there is difficulty of obtaining loans, and the rate of interest is high,--it is concluded that this must arise from causes acting upon the quant.i.ty of money in the other and more popular sense; that the circulating medium must have diminished in quant.i.ty, or ought to be increased. I am aware that, independently of the double meaning of the term, there are in the facts themselves some peculiarities, giving an apparent support to this error; but the ambiguity of the language stands on the very threshold of the subject, and intercepts all attempts to throw light upon it.
As countless words and expressions have several meanings, there is almost no limit to the confusion which this fallacy can cause. Some of the most common terms that are used ambiguously are _right_, _liberty_, _law_, _representative_, _theory_, _church_, _state_, _student_.
By carefully defining all terms that have more than one meaning and by insisting on a rigid adherence to the one meaning wherever the term is used, a debater can easily avoid fallacies of this sort in his own argument and expose those of his opponent.
III. FALSE CAUSE.
The fallacy of false cause occurs whenever that which could in no way bring about the effect that is being established is urged as its cause. This fallacy in its most obvious form is found only in the arguments of careless and illogical thinkers. Some college students occasionally draw briefs that contain such reasoning as the following:--
I. The Panama ca.n.a.l should be of the sea-level rather than of the lock type, because
A. The Panama ca.n.a.l will do away with the long voyage around the Horn.
I. Southerners are justified in keeping the franchise away from the negro, for
A. Negroes should never have been brought to America.
B. The Fifteenth Amendment to the Const.i.tution ought not to have been pa.s.sed.
The error of such plainly absurd reasoning as occurs in the preceding ill.u.s.trations needs no explanation. There is one form of the fallacy of false cause, however, that is much more common and insidious and therefore deserves special treatment.
POST HOC ERGO PROPTER HOC. (After this, therefore, on account of this.) This phase of the fallacy consists of the a.s.sumption that since cause precedes effect what has preceded an event has caused it. The most frequent occurrence of the error is to be found in superst.i.tions.
If some one meets with an accident while taking a journey that began on Friday, many people will argue that the accident is the effect of the unlucky day. Some farmers believe their crops will not prosper unless the planting is done when the moon is in a certain quarter; sailors often refuse to embark in a renamed vessel. Because in the past, one event has been known to follow another, it is argued that the first event was the cause of the second, and that the second event will invariably follow the first.
But this fallacy does not find its only expression in superst.i.tions.
To _post hoc_ reasoning is due much of the popularity of patent medicines. Political beliefs, even, are often generated in the same way; prosperity follows the pa.s.sing of a certain law, and people jump to the conclusion that this one law has caused the ”good times.” Some demagogues go so far as to say that education among the Indians is responsible for the increased death rate of many of the tribes.
A slightly different phase of the _post hoc_ fallacy consists in attributing the existence of a certain condition to a single preceding event, when at the most this event could have been only a partial cause of what followed, and may not have been a cause at all. A medicine that could not have effected a cure may have been of some slight benefit. A law that could not possibly have been the sole cause of ”good times” may have had a beneficial effect. To avoid this fallacy, one must be sure not only that the a.s.signed cause is operative, but that it is also adequate.
<script>