To die; to sleep;
No more; and by a sleep to say we end
The heart-ache and the thousand natural shocks
That flesh is heir to. 'Tis a consummation
Devoutly to be wish'd. To die; to sleep;—
To sleep? Perchance to dream! Ay, there's the rub;
For in that sleep of death what dreams may come,
When we have shuffl'd off this mortal coil,
Must give us pause.
But, as in this case of Hamlet's, poetical analogies will not bear much strain; the aspect in which the similarity holds is usually the only aspect the two cases have in common, and to take poetry as a precise formulation of fact is to sin against both humor and sound reasoning.
In daily life we are constantly reasoning by analogy. If you argue that a certain man who has been successful at the head of a railroad will therefore make a good president for a college because that also is a complex institution, or that because self-government has worked well in a certain school it will probably work well in a college, or that because a friend has been cured of sleeplessness by taking a walk just before going to bed therefore everybody who sleeps badly can be cured in the same way,—in all these cases you are reasoning by analogy. In each case it will be noticed you would pass from a similarity which exists in a single case or in a small number of cases to the conclusion. The reasoning is sound, however, only in so far as the similarity bears on the actual purpose in hand: in the first example, if the success of the railroad president arises from the power of understanding men and of philosophic insight into large problems, the reasoning will probably be valid; in the last example, if applied to insomnia due to overwork, it might be bad.
In practical affairs it is easy to find examples of reasoning from analogy, especially in arguments of policy. The first trial of city government by commission depended on such reasoning: when Galveston, Texas, was devastated by a storm it was reasoned that in business matters a small body of picked men with absolute powers are most efficient in an emergency, and that since the reconstruction of the city was essentially a matter of business, such a body would best meet the emergency. So the extension of commission government in other states at first followed reasoning by analogy: government by commission worked well in Galveston; it would probably work well in Des Moines. In the same way with the arguments for a parcels post: they proceed from the analogy of the present postal service, which has been successful so far as it goes, and from the success of the parcels post in almost all the countries of Europe. If you were arguing that "Association" (or "soccer") football should be made one of the major sports at your college, you would reason from the analogy of its great popularity with Englishmen all over the world that it would also probably be popular in America.
When you use the argument from analogy, however, you must make sure that the similarity between the two cases runs to the point you wish to establish. In the following extract from an argument in favor of commission government for all cities, the author explicitly limits his reasoning from the analogy of Washington to the point of the extension of the system to large cities.
If we look for successful governments by commission in this country, it is not difficult to find them in our largest cities. The city of Washington is governed by a small commission, and is acknowledged to be one of our best-governed cities. While this commission originated in an entirely different way from that of the commission form of government, successful administration under its rule is a valid answer to the argument that small commissions are suited only to the administration of small cities.[26][!--Note--]
Whenever you use this type of reasoning, it is wise thus to limit its bearing. If in an argument in favor of allowing secret societies in a high school you rely on the analogy of college life, take pains to show that the resemblance covers the social life of a school. If you were arguing that your city should establish a municipal gymnasium, and relied on the reasoning from the analogy of a family, in which all the members have a direct interest in the health of the others, show that this interest has practical grounds of welfare, and does not rest wholly on affection. In every case, unless the limits of the analogy are obvious, specify them in order to carry your readers safely with you.
35. False Analogy. A peculiar danger of the argument from analogy is the fallacy which is known as false analogy, or reasoning to a conclusion which the similarity does not support. Arguments in which there are many figures of speech, especially when the style is at all florid, are apt to slop over into this fallacy. To liken education to the unfolding of a flower is all very well, if you do not go on to argue that because the lily of the field neither toils nor spins, therefore a child should do no work in school. It is said that M. Stolypin, the late premier of Russia, once half apologized In the Duma for the slowness of his reforms, saying that he Was like a man shooting with a flintlock musket; to which one of the Liberal members replied that it was not a question of weapons, but of aim, and that if his Excellency was to go on shooting at the people, it would be better if he went on using flintlocks.
Under the auspices of the Carnegie Institution an expert in business administration made an inquiry into the methods of teaching and research in physics at various American universities, and made recommendations based on the conduct of business establishments. A professor of physics in answer showed in how many ways the analogy between a business concern, whose end is profit, and a physical laboratory, whose end is the advancement of knowledge, is false and misleading. The expert had suggested a general research board to correlate researches; the professor cited the cases of Airy, the astronomer royal of England, who by his dominating position held back astronomical research in England for a generation, and of Sir Humphry Davy, who discouraged the work of Faraday, when the latter was his assistant. The expert suggested that apparatus could be passed on from one investigator to another: the professor replied that few men can use apparatus designed for some one else's purpose, and that the cost of reconstruction would exceed the cost of new machines. In short, he completely riddled the argument from analogy set up by the expert.[27][!--Note--]
A notable example of conclusive refutation of an argument based on a false analogy is to be found in William James's Ingersoll Lecture on Immortality. He took up the ordinary argument against the immortality of the soul, which, starting from the accepted physiological and psychological formula, "Thought is a function of the brain," reasons that therefore when the brain dies and decays, thought and consciousness die, too.