An argument on the tariff, for example, sometimes runs off into appeals to save this grand country from ruin or from the trusts or from some other fate which the speaker pictures as hanging over an innocent and plain people.  An argument for the restoration of the classical system of education which should run off into eulogies of the good old times might easily become an argumentum ad populum; an argument in favor of a new park which should dwell on selfish advantages which might be gained by the abutters without regard to larger municipal policy would probably be an argumentum ad hominem.

Obviously these two forms of shifting the issue trench closely on the element of persuasion in an argument, and in making the distinction you must apply common sense.  Your adversary may reprove you for an argumentum ad hominem or ad populum, when you believe that you are keeping well within the bounds of legitimate persuasion; but in general it is safe to guard your self-respect by drawing a broad line between dodging and unworthy appeals to prejudice and justifiable appeals to feeling and personal interest.

EXERCISES

1.  Name a question of policy which would be settled by the establishment of some controverted fact.

2.  Find in the daily papers an account of a trial in which evidence was declared inadmissible under the rules of law which would have been taken into account by the average man outside the court in making up his own mind.

3.  Name three questions in which the evidence would be affected by temperamental and other prepossessions of the witness.

4.  Name a scientific question in which some important fact is established by reasoning from other facts.

5.  Cite a case, either from real life or from fiction, in which a fact was established by circumstantial evidence; analyze the evidence and show how it rests on reasoning from similarity.

6.  Give a case in which what you believed to be direct observation of a fact deceived you.

7.  Give an example from your own experience within a week where vague authorities have been cited as direct evidence.

8.  What would you think of the writer of the following sentences as a witness to the numbers and importance of the participants in the woman suffrage procession he is reporting?

Fifth Avenue has seldom, if ever, been more crowded than on Saturday afternoon, and never anywhere have I seen so many women among the spectators of a passing pageant.  Throngs, many tiers deep, flanked the line of march, and these throngs were overwhelmingly composed of women.  As I passed from block to block I could not get away from the thought that the vastest number of these were sick of heart and ashamed that they, too, were not in line behind the kilted band that headed the procession, the historic symbolic floats, and the