E. The conclusion must be reasonable.

After all the foregoing requirements have been met there still remains one essential. The conclusion must be reasonable. This is the ultimate test of validity. We have become so familiar with the usual course of nature that we instinctively question that which appears to run contrary thereto. Nothing occurs without an adequate cause. Upon this principle we base our judgment regarding all matters which transcend our own experience. Most of us have passed the superstitious days when the breaking of a looking glass was regarded as a sure sign that someone in the family would die before the end of the year. Even the time-honored Friday and number thirteen with their attendant superstitious disasters no longer have a large following. Scientific investigation and the present age of commercialism have crowded out superstition and put common sense in its place. The average mind is highly reasonable and requires some causal connection between the breaking of a looking glass and the death of a person. It would refuse to believe that one caused the other, or that one was the sign of the other, even though there might be a hundred instances to warrant the induction and not one to contradict it. The final requirement for an imperfect inductive argument is that it be reasonable.

SUMMARY OF REQUIREMENTS FOR AN IMPERFECT INDUCTIVE

ARGUMENT

1. The number of specific instances supporting the conclusion must be sufficiently large to offset the probability of coincidence.

2. The class of persons, events, or things about which the induction is made must be reasonably homogeneous.

3. The specific instances cited in support of the conclusion must be fair examples.

4. Careful investigation must disclose no exceptions.

5. The conclusion must be reasonable.

EXERCISES

1. Are the following inductions perfect or imperfect? . (1) All men are mortal.

(2) All Irving's books are interesting (or uninteresting).
(3) All the presidents of the United States who have
been assassinated were Republicans.

(4) "Pythagoras was misunderstood, and Socrates, and
Jesus, and Luther, and Copernicus, and Galileo, and
Newton, and every pure and wise spirit that ever
took flesh. To be great is to be misunderstood."
Emerson, Self-Reliance

(5) Money is the root of all evil.

2. Give in full the specific instances upon which each of the foregoing inductions is based.

3. Apply the requirements for validity to each of the inductions in exercise one, and state the result.

4. Write an inductive argument of four hundred words.

CHAPTER II

DEDUCTIVE ARGUMENT

This

Deductive argument consists of the application of deductive processes of reasoning to argumentative discourse. process of applying logical principles is somewhat more complicated than that involved in induction. In some respects it is more important that the student thoroughly master deduction than it is that he master induction. Fallacies are more easily concealed in the deductive process than in the inductive process. Nevertheless, when the fallacy is once detected it can be set forth clearly by anyone who understands this form of reasoning. Neither the inductive nor the deductive form of reasoning is often found alone. Most arguments contain both of these processes and in some cases they are very closely interwoven. This fact necessitates a thorough study of both processes. From this standpoint a knowledge of one form is as important as a knowledge of the other. In order that we may thoroughly understand the application of the deductive process to argument we must first consider separately that process of reasoning.

I. Deductive reasoning.

By deductive reasoning we arrive at a conclusion regarding a particular person, event, or thing by reason of our knowledge regarding the whole class to which the particular person, event, or thing belongs. In this sense it is the opposite of induction. We conclude that a particular book is interesting because we know that all the books written by the author of

this book are interesting. We may say that deductive reasoning begins where inductive reasoning leaves off. For example, we found that we could arrive at the imperfect inductive conclusion that all of Stevenson's books are interesting because each one of a number of his books which we had read was interesting. Since (1) the number of specific instances cited were sufficient to offset the probability of coincidence, (2) the class was fairly homogeneous, (3) the examples were fair, (4) we found upon investigation that there were no exceptions, and (5) from the character of the author and other circumstances the conclusion seemed reasonable, we concluded that our induction was sound. Now, taking this conclusion as true we may apply it to any one of Stevenson's works not yet examined and thus determine that that work is interesting. It must be kept in mind, however, that a deduction based upon an imperfect induction is no stronger than that imperfect induction. The imperfect induction gains no strength by reason of its having a valid deduction based upon it. Nevertheless, unsound arguments are often given a superficial appearance of validity by this

means.

We may more clearly indicate the relation of the inductive and the deductive process by arranging the material of the foregoing illustration in the following manner.

A. Inductive process.

1. Specific instances.

(1) Treasure Island, written by Stevenson is interesting.
(2) Kidnapped, written by Stevenson is interesting.
(3) David Balfour, written by Stevenson is interesting.
(4) Prince Otto, written by Stevenson is interesting.
(5) St. Ives, written by Stevenson is interesting.

2. Conclusion: All books written by Stevenson are interesting.

B. Deductive process.

1. Major Premise: All books written by Stevenson are interesting.

2. Minor Premise: The Silverado Squatters was written by Stevenson.

3. Conclusion: Therefore The Silverado Squatters is inter

esting.

It will be observed that the inductive conclusion forms the first statement, the basis, or what is called in logic, the major premise of the deductive process. By induction we build several specific instances into a conclusion, and from that conclusion we reason down again to one particular instance. This illustration should serve to make plain to the student the relation between induction and deduction and the reason why the two processes are so often combined in an argument.

In logic the deductive form presented above is called a syllogism. It consists of three statements called Major Premise, Minor Premise, and Conclusion. This syllogism occurs in different forms, but we are concerned with only the typical form above presented, because it is to this form that we intend to reduce our own arguments and the arguments of our opponents in order that we may test their validity.

Each statement in a syllogism is composed of two parts, called terms. The names of these terms as well as their proper location in the syllogism are indicated by the following form:

1. Major Premise: All college men should study argumentation.

Minor term. Middle term.

2. Minor Premise: Paul Morton is a college man.

3. Conclusion: Therefore Paul Morton should study argumentation.