3. Under these conditions an inheritance tax should be levied.
4. International arbitration will ultimately take the place of war as a method of settling disputes between nations.
IV. Analyze completely the reasoning processes employed in Exercise III. Where they may be reduced to syllogistic form, determine the validity of the resulting syllogisms.
V. Write an argument from causal relation in support of any proposition which you wish to discuss. Employ each of the three classes of argument from causal relation.
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.”