quirements 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 em

ployed 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