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 canal should be of the sea-level rather than of the
lock type, because
A. The Panama canal 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 Constitution ought not to have been passed.
The error of such plainly absurd reasoning as occurs in the preceding illustrations 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 assumption 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 superstitions. 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 superstitions. 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 passing 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.