“‘Upon the first hypothesis, the assumption is that phenomena of Nature similar to those exhibited by the present world have always existed; in other words, that the universe has existed from all eternity in what may be broadly termed its present condition.
“‘The second hypothesis is, that the present state of things has had only a limited duration; and that at some period in the past, a condition of the world, essentially similar to that which we now know, came into existence, without any precedent condition from which it could have naturally proceeded. The assumption that successive states of Nature have arisen, each without any relation of natural causation to an antecedent state, is a mere modification of this second hypothesis.
“‘The third hypothesis also assumes that the present state of things has had but a limited duration; but it supposes that this state has been evolved by a natural process from an antecedent state, and that from another, and so on; and on this hypothesis, the attempt to assign any limit to the series of past changes is usually given up.’
“Huxley thus destroyed the first two hypotheses and left the third—since called the Theory of Evolution—standing alone. Following this indirect, destructive method of proof, Huxley offered direct, constructive proof of the probable soundness of the Theory of Evolution. Such positive proof should always be offered in corroboration of negative proof, for the method of residues is, at best, only an indirect argument. The chances of overlooking a possibility, or of failing completely to destroy those dealt with, are so great that the result of the indirect method should be reinforced by direct argument.”
V. Inconsistencies.
When a witness testifies in a court of law he injures his own credibility as soon as one part of his story contradicts another part. His entire account of the events about which he has been called to give testimony must be consistent. Any inconsistency may prove fatal to the acceptance of his testimony. In like manner any inconsistency in an argument may prove fatal to its acceptance. The exposure of such inconsistencies in an opponent’s argument is one of the most important methods of refutation. In most cases the difficulty of the task is greatly increased by the form in which such inconsistencies usually occur. Seldom are they apparent. In most cases the error is revealed only after the argument has been carefully analyzed and the inconsistent parts stripped of their covering of confusing language.
The following quotation taken from the argument of Lincoln in one of the Lincoln-Douglas debates shows the application of this method. Douglas had maintained that slavery could be lawfully excluded from a territory in spite of the Dred Scott decision. In refuting this argument by exposing the inconsistency which it contained, Lincoln said:—
“The Dred Scott Decision expressly gives every citizen of the United States a right to carry his slaves into the United States Territories. Now, there was some inconsistency in saying that the decision was right, and saying, too, that the people of the Territory could lawfully drive slavery out again. When all the trash, the words, the collateral matter, was cleared away from it,—all the chaff was fanned out of it,—it was a bare absurdity: no less than that a thing may be lawfully driven away from a place where it has a lawful right to be. Clear it of all the verbiage, and that is the naked truth for his proposition—that a thing may be lawfully driven from the place where it has a lawful right to stay.”
VI. Adopting an opponent’s evidence.
This method of refutation consists in taking evidence which an opponent has introduced in favor of his own argument and showing that in reality it supports the opposite contention. This method of refutation is so effective that it should never be neglected when an opportunity to use it is presented. The opportunity may arise from the failure of an opponent to grasp the full bearing of the evidence which he offers, or it may arise from an unexpected turn in the discussion. Evidence may be introduced in the beginning of a discussion to support a particular contention by which it favors the writer or speaker who introduces it. Later this same evidence may be interpreted as supporting a contention entirely adverse to the writer or speaker who introduced it. An excellent example of this method of refutation is found in Bouton’s Lincoln and Douglas Debates in Lincoln’s Cooper Institute Speech, where he turns the warning of Washington against those who had been quoting it against him.