I remember Richardson's grandson well; he was a clergyman in the city of London; he was a most upright and excellent man; but he had conceived a strong prejudice against works of fiction. He thought all novel-reading not only frivolous but sinful. He said—this I state on the authority of one of his clerical brethren who is now a bishop—he said that he had never thought it right to read one of his grandfather's books.
I will give another instance. One of the most instructive, interesting, and delightful books in our language is Boswell's Life of Johnson. Now it is well known that Boswell's eldest son considered this book, considered the whole relation of Boswell to Johnson, as a blot in the escutcheon of the family.
Thomas Babington Macaulay: Copyright, 1841
Analogy. In argument by analogy the speaker attempts to prove that because certain things are known to be true in something that can be observed they are likely to be true in something else which in so far as it can be observed is quite like the first. We continually argue by analogy in daily life. Lincoln was really using analogy when he replied to the urging to change his army leaders during the Civil War, that he didn't think it wise to "swap horses while crossing a stream." Scientists use this method to draw conclusions when it is impossible to secure from actual observation or experiment a certain last step in the reasoning. The planet Mars and the earth are similar in practically all observable matters; they are about the same distance from the sun, they have the same surface conditions. The earth has living creatures upon it. Hence—so goes the reasoning of analogy—Mars is probably inhabited. Reasoning by analogy is used to prove that universal suffrage is good for the United States because it has been good for one particular state. A student may argue by analogy that the elective system should be introduced into all high schools, because it has been followed in colleges. It may be asserted that a leading bank president will make a good university president, because he has managed one complex institution. The essence of all good reasoning by analogy is that the two things considered must be so nearly alike in all that is known that the presumption of belief is that they must also be alike in the one point the arguer is trying to establish. This is the test he must apply to his own analogy arguments.
Our community frowns with indignation upon the profaneness of the duel, having its rise in this irrational point of honor. Are you aware that you indulge the same sentiment on a gigantic scale, when you recognize this very point of honor as a proper apology for war? We have already seen that justice is in no respect promoted by war. Is true honor promoted where justice is not?
Charles Sumner: The True Grandeur of Nations, 1845
Residues. The method of residues is frequently employed when the speaker is supporting a policy to be carried out, a measure to be adopted, a change to be instituted, or a law to be passed. Granting the assumption that something must be done he considers all the various methods which may be employed, disposes of them one by one as illegal, or unsuited, or clumsy, or inexpedient, leaving only one, the one he wants adopted, as the one which must be followed.
This is a good practical method of proof, provided the speaker really considers all the possible ways of proceeding and does show the undesirability of all except the one remaining.
A speaker pleading for the installation of a commission form of city control might list all the possible ways of city government, a business manager, a mayor, a commission. By disposing completely of the first two, he would have proven the need for the last. A good speaker will aways go farther than merely to reach this kind of conclusion. He will, in addition to disproving the unworthy choices, strongly support his residue, the measure he wants adopted. In supporting amounts of taxes, assessments, etc., this method may be used. One amount can be proven so large as to cause unrest, another so small as to be insufficient, a third to produce a total just large enough to meet all anticipated expenses with no surplus for emergencies; therefore the correct amount must be just larger than this but not reaching an amount likely to produce the result caused by the first considered. Used in trials of criminal cases it eliminates motives until a single inevitable remainder cannot be argued away. This may be the clue to follow, or it may be the last one of all suspected persons. Burke considered several possible ways of dealing with the American colonies; one he dismissed as no more than a "sally of anger," a second could not be operated because of the distance, a scheme of Lord North's he proved would complicate rather than settle matters, to change the spirit of America was impossible, to prosecute it as criminal was inexpedient, therefore but one way remained, to conciliate the spirit of discontent by letting the colonies vote their own taxes. It is interesting that what Burke described as the sally of anger was the way the matter was actually settled—Great Britain had to give up the American colonies.
This method is also called elimination.