CHAPTER IV

ARGUMENT FROM ANALOGY

Analogy is such a resemblance between some of the known characteristics of two different things as will lead to the conclusion that they are alike in other characteristics. For example, an egg and a seed are two different things but they have many characteristics in common. From the characteristics in which we know that an egg is like a seed we reason that they must be alike in other characteristics which we know one to possess but which we do not know the other to possess. We know that heat is required to develop an egg and by analogy we may conclude that heat is required to develop a seed. In this, as in other forms of reasoning, we proceed from the known to the unknown. The basis of inference is the general resemblance which one thing bears to another thing. Experience has led us to expect that when we find two different things alike in many points we shall find them alike in many other points regarding which no actual investigation has been made.

The argument applies the principle above suggested to the subject-matter of the discussion. The standard illustration of this form of argument usually quoted in books of logic and argumentation is found in Reid’s _Intellectual Powers_. It is as follows:—

“We may observe a very great similitude between this earth which we inhabit, and the other planets, Saturn, Jupiter, Mars, Venus, and Mercury. They all revolve around the sun, as the earth does, although at different distances and at different periods. They borrow all their light from the sun, as the earth does. Several of them are known to revolve on their axis like the earth, and by that means have like succession of day and night. Some of them have moons that serve to give them light in the absence of the sun, as our moon does to us. They are all in their motions subject to the same law of gravitation as the earth is. From all this similitude it is not unreasonable to think that these planets may, like our earth, be the habitation of various orders of living creatures. There is some probability in this conclusion from analogy.”

Another frequently quoted illustration of the argument from analogy is the reply of Abraham Lincoln to those who urged him to carry on the war more vigorously.

“Gentlemen, I want you to suppose a case for a moment. Suppose that all the property you were worth was in gold, and you had put it in the hands of Blondin, the famous rope-walker, to carry across the Niagara Falls on a tight rope. Would you shake the rope while he was passing over it, or keep shouting to him, ‘Blondin, stoop a little more! Go a little faster!’ No, I am sure you would not. You would hold your breath as well as your tongue, and keep your hands off until he was safely over. Now the government is in the same situation. It is carrying an immense weight across a stormy ocean. Untold treasures are in its hands. It is doing the best it can. Don’t badger it! Just keep still and it will get you safely over.”

The argument from analogy is most effective when a comparison is made to something that is plain, ordinary, and commonplace. In this way abstract arguments may be made simple and concrete. No debater of modern times has shown more discrimination in the use of material which would make an analogy strong and convincing than has Lincoln. The strength of the argument is greatly increased if it is apparent that the analogy is perfect so far as the point at issue is concerned. In the following quotation no exercise of the imagination is necessary to bring the two factors of the analogy together. The argument is presented by David Dudley Field in favor of the training of homeless children by the state.

“The question of safety is more vital still. Every one of these boys may be a voter in ten or twenty years hence. His vote will then be as potent as yours or mine. In countries where the sovereign is a prince it has ever been thought prudent to bestow especial care upon the training of an heir to the throne.—Here the people are sovereign, and the little boy, now wandering about the streets, neglected or led astray, is in one sense joint heir to the throne. Every dictate of prudence points to his being fitted to fulfill the duties of his station.”

The foregoing examples with the accompanying explanations will serve to make plain the meaning of argument from analogy and to suggest the innumerable circumstances under which it may be used. Seldom is a situation encountered in which an apt analogy cannot be employed. The homelier the comparison, the more vivid and lasting will be the impression conveyed, provided, of course, that the analogy is apt and appropriate.

The search for an appropriate analogy is best begun by gaining a clear conception of the universal principle upon which the proposition is based. The student must be able to see the broadest application of the reason which he offers in support of any particular contention. Having grasped this fundamental principle it is easy to see its application in other things of a more tangible form and which are more familiar to the average mind. For example, Lincoln saw that it would not do to pursue the Civil War too vigorously. He realized that the government was in a very perilous position, that every step must be taken with care and deliberation and that the least disturbance from those whose interests were at stake might mean failure and the loss of everything. This was the principle underlying the situation which he was facing. Now, he must make this situation plain and its gravity clear to those who were demanding that he hasten the progress of the war. Therefore he began looking for the application of this principle in something which was more familiar and more real and tangible. The newspapers had been full of the wonderful feats of Blondin, the rope-walker. In this circumstance Lincoln saw an opportunity to give a tangible exhibition of the application of the principle under which he was acting.

The argument from analogy which he constructed is a model of completeness. He compared abstract things which could not be seen and appreciated with tangible things which could be seen and appreciated. He compared the Government to Blondin. Blondin, walking on a rope across Niagara Falls, was in a very dangerous position where it was necessary that he move slowly and cautiously because the least misstep would dash him to destruction. The situation of the government was analogous. It was engaged in a very dangerous undertaking, a great civil war. It had to move slowly and cautiously because the least misstep would mean destruction. In order to make the analogy more complete Lincoln supposed the case of Blondin performing this feat carrying with him all the worldly possessions of the men who were urging that the war be pushed more vigorously. The government was carrying out the dearest desire of the people, the patriotic desire to save the grandest of all nations. If the government failed it would mean the blighting of their dearest hopes and to many it would mean financial ruin. Therefore the analogy was complete in that particular. Now these men were here in Washington doing the same thing to the government that they would be doing if, under the above circumstances, they shook the rope or scolded Blondin while he was walking across Niagara Falls. The forcibleness of the analogy and the vividness of the impression which it conveyed was an argument powerful enough to silence those who were demanding more aggressive action on the part of the government.

An argument from analogy is never conclusive proof of the truth or falsity of a proposition. At best it creates only a high degree of probability. Its greatest use is to give force and vividness to an argument already established by other means. Nevertheless, its probative value is great provided it is properly constructed. The chance for error, however, is a constant source of danger to him who relies upon analogy, for the very facts upon which it is based may constitute the reason for its falsity. A large oil refining company was recently organized. People were induced to buy stock in the new enterprise by means of argument from analogy. It was argued that this company was similar to the Standard Oil Company. Now it is well known that the Standard Oil Company pays large dividends. The argument was advanced by the promoters of the new organization that since it was similar to the Standard Oil Company and since the latter corporation pays large dividends, therefore the new corporation would pay large dividends. The analogy, of course, proved untrustworthy. The companies, though similar in many ways, were entirely different in one essential particular effecting the conclusion: the old company had entirely monopolized the field of activity, while the new company had no territory in which to work. Thus a false analogy led to the loss of many thousands of dollars.

Instances of unsound arguments from analogy might be multiplied indefinitely. It is therefore evident that certain requirements exist which must be strictly complied with if the argument from analogy is to prove effective. The requirements necessary for a valid argument from analogy are as follows:

I. The two factors in the analogy must be alike in all particulars which affect the conclusion.

The two factors in the analogy are the thing about which the analogy is made and the thing to which it is compared. For example, in the argument from analogy which we have quoted from Lincoln, the first factor is the position of the government during the Civil War and the second factor is the rope-walker. The former is the thing about which the argument is made; the latter is the thing to which the first factor is compared. These two parts exist in every argument from analogy and the first requirement is that they agree in everything which affects the conclusion. The conclusion Lincoln wished to establish was that the government must not be disturbed in its action because it was in a dangerous position. A rope-walker crossing Niagara Falls must not be disturbed because he is in a dangerous position. These are the facts which affect the conclusion in each case. The two factors are alike in this particular.

From the above example it will be seen that the two factors must agree in the essential particulars. What is essential depends upon the nature of the conclusion to be reached. In particulars affecting things other than the conclusion to be established, it matters not whether they agree or disagree. In comparing an illegal private monopoly to a highwayman the particular method of robbing the victim is immaterial. The fact that the two methods are not exactly alike does not weaken the force of the analogy.

Burke made use of the argument from analogy in defending the policy of conciliation which he favored. After urging that the colonies be granted representation in Parliament, he declared that so far as government was concerned there were four similar cases,—Ireland, Wales, Chester, and Durham. He urged that the acts of Parliament with regard to these territories be applied to America. He then proceeded to show that the analogy was sound by pointing out that the two factors agreed in all particulars which affected the conclusion. He said,

“Are not the people of America as much Englishmen as the Welsh? The preamble of the Act of Henry the Eighth says the Welsh speak a language no way resembling that of his Majesty’s English subjects. Are the Americans not as numerous? If we may trust the learned and accurate Judge Barrington’s account of North Wales, and take that as a standard to measure the rest there is no comparison. The people cannot amount to above 200,000, not a tenth part of the number in the colonies. Is America in rebellion? Wales was hardly ever free from it. Have you attempted to govern America by penal statutes? You made fifteen for Wales. But your legislative authority is perfect with regard to America. Was it less perfect in Wales, Chester, and Durham? But America is virtually represented. What! does the electric force of virtual representation more easily pass over the Atlantic than pervade Wales, which lies in your neighborhood—or than Chester and Durham, surrounded by an abundance of representation that is actual and palpable? But, Sir, your ancestors thought this sort of virtual representation, however complete, to be totally insufficient for the freedom of inhabitants of territories that are so near and comparatively so inconsiderable. How then can I think it sufficient for those which are infinitely greater and infinitely more remote?”

It will be observed that there is a slight difference in the analogy here employed and the one of which Lincoln made use. In the latter the factors are entirely unlike, in the former they are similar. In all analogies similar to that employed by Burke the points of similarity in the two factors must be clearly shown to bear directly upon the conclusion, whereas if any points of difference exist they must be shown to have no vital bearing on the question at issue.

A failure to observe this application of the rule was made by a student who argued that because an income tax had worked well in other countries it would work well in the United States. His opponent pointed out the unsoundness of the analogy by showing that the income tax proposed for the United States was a progressive tax, whereas the income tax in the foreign countries cited was not a progressive tax. He further revealed the falsity of the analogy by showing that the proposed income tax for the United States was to be levied by the national or Federal government, whereas the income tax in the foreign countries cited was levied by the states or smaller governmental units of those countries. The analogy was shown to be false in that the two factors did not agree in all particulars affecting the conclusion because (1) in one factor the tax was progressive while in the other it was not, and (2) in one factor the tax was levied by the national government and in the other it was not.

The argument from analogy can be made stronger if it is shown that what is true of the analogous case is much more likely to be true and to be true in a greater degree, of the case in dispute. The example of analogy quoted from Burke shows this phase of the process. Some writers call this process an intensification of the argument from analogy. In logic it is _a fortiori_ reasoning. The Scriptures abound in this kind of argument, such as “Are not two sparrows sold for a farthing? and one of them shall not fall on the ground without your Father. Fear ye not therefore; ye are of more value than many sparrows.” Another passage illustrating the intensification of the argument from analogy is, “Consider the ravens; for they neither sow nor reap; which neither have storehouse nor barn; and God feedeth them; how much more are ye better than the fowls?”

In a debate on the proposition, “Resolved, that courses of instruction in the care and training of children should form a part of the curriculum of every college and university,” a speaker for the affirmative developed an analogy based upon the similarity between such a course and the practical courses in the College of Agriculture on the raising of live stock. He then gave force to his analogy by suggesting that if it were worth while to give college courses dealing with the raising of colts, calves, and pigs, it certainly would be much more worth while to give courses dealing with the raising of children.

=II. The alleged facts upon which the analogy is based must be true.=

The facts alleged to be true in regard to each of the factors in the analogy must be true as a matter of fact. A deviation from the truth in either factor will invalidate the conclusion. In arguing in favor of the municipal ownership and operation of the street railway system in an eastern city a debater declared that the proposed plan would be successful because it had been tried in Chicago with great success. He then spent much time in showing that so far as street railway ownership was concerned conditions in the two cities were exactly alike. This argument from analogy, however, was promptly overthrown by the next speaker, who introduced evidence which proved that the city of Chicago did not own its street railway system. The analogy was unsound because one of the alleged facts upon which it was based was not true.

The above example illustrates one of the chief sources of error in the use of this class of argument. The student must be constantly on his guard when inspecting his own work and that of his opponent. The argument from analogy demands extensive and accurate knowledge of both the factors involved and the result is almost always in favor of him whose knowledge of the subject-matter is the most comprehensive. The temptation to color the facts in order to fit the analogy is sometimes great and to refrain from deceiving one’s self as well as one’s hearers requires a high degree of intellectual honesty. In no other form of argument is the demand for absolute impartiality more imperative. An analogy which extends beyond the sound foundation of real facts is a constant source of danger both for him who proposes it and for him who receives it. All the alleged facts upon which this kind of argument is based must be true.

III. The conclusion established by analogy should be verified by positive evidence whenever possible.

The suggestion has already been made that no matter how perfect an analogy may be, it can never amount to absolute proof. At its best analogy creates only a high degree of probability. In order to strengthen the conclusion a diligent search should be made for other lines of reasoning which will fortify it. One of the most important uses to which analogy may be put is to suggest possible conclusions which may be substantiated by other processes of reasoning, as induction, deduction, or causal relation. If two or more lines of reasoning can be made to support the same conclusion the probability of its truth is greatly strengthened; hence its argumentative value is increased. Where all available processes of reasoning may be made to establish one conclusion the probability of its truth is so strengthened that it amounts to moral certainty, but no cumulation of probabilities can ever amount to absolute certainty.

The fact that analogy must be substantiated by other processes of reasoning should not lead the student to underestimate its importance. The examples and explanations which have been given should lead him to appreciate fully the fact that analogy has two well defined uses aside from its value as proof of the truth or falsity of a conclusion. In the first place it is a most important agency in suggesting conclusions which may be verified or discredited by other processes of reasoning. In the second place it affords a most valuable method of stating a case so plainly that even the most ignorant may understand. A striking analogy makes a most vivid impression on the mind and is retained long after more formal processes of reasoning are forgotten.

SUMMARY OF THE REQUIREMENTS FOR AN ARGUMENT FROM ANALOGY

I. The two factors in the analogy must be alike in all particulars which affect the conclusion.

II. The alleged facts upon which the analogy is based must be true.

III. The conclusion established by analogy should whenever possible be verified by positive evidence.

EXERCISES IN ANALOGY

I. Apply the requirements for validity to each of the arguments from analogy quoted in this last chapter.

II. Suggest arguments from analogy in support of each of the following conclusions:

1. College students should be allowed to select their own courses of study.

2. A course in public speaking is a necessity for those who expect to teach.

3. The greatest moral strength is fostered among many temptations.

4. An inheritance tax is an exceedingly just method of taxation.

5. All colleges should be coëducational.

6. Military drill should be compulsory for all college freshmen.

7. The use of clear and correct English is a prerequisite to success in any profession.

III. Write an argument from analogy in support of one of the propositions given in the appendix.