The chapter on Argument from Analogy treated of the requirements for validity to which such an argument must conform. We may expose the fallacy of an argument from analogy by showing—
1. That the two factors in the analogy are not alike in all the particulars affecting the conclusion.
2. That the alleged facts upon which the analogy is based are not true.
3. That the conclusion established by analogy is disproved by positive evidence.
No test of an analogy is absolute. Its very nature makes it more susceptible to fallacy than are the other forms of argument. At its best it creates only a high degree of probability. As already stated, its chief use is to give clearness and force to persuasive writing and speaking. In the search for fallacies, here as well as elsewhere, the best guarantee of success is an unprejudiced mind equipped with a thorough working knowledge of all the argumentative processes of reasoning and of the numerous fallacies to which they are subject.
EXERCISES IN FALLACY
I. Point out clearly the kind of fallacies, if any, involved in the following arguments.
1. The only people excluded from the privilege of voting are children, idiots, foreigners, convicts, and women. How much longer will the civilized nations of the earth permit their women to be classed with the incompetent and the criminal classes of society?
2. Political parties are a necessity to free institutions. The United States is the oldest democracy on earth and in it political parties have always ruled.
3. The election of a Republican president in 1896 was followed by a period of prosperity unrivalled in our history. Who can doubt that had a Democratic president been elected it would have worked the beginning of a sure decline of our industrial supremacy?