Hasty Generalization.  The speaker cannot himself examine all the specific instances, he cannot consider all the illustrations which might support his position, but he must be careful of a too hasty generalization.  Having talked with a dozen returned soldiers he may not declare that all American army men are glad to be out of France, for had he investigated a little further he might have found an equal number who regret the return to this land.  He must base his general statement on so many instances that his conclusion will convince not only him, but people disposed to oppose his view.  He must be better prepared to show the truth of his declaration than merely to dismiss an example which does not fit into his scheme by glibly asserting that “exceptions prove the rule.”  He must show that what seems to contradict him is in nature an exception and therefore has nothing at all to do with his rule.  Beginning speakers are quite prone to this fault of too hasty generalization.

EXERCISES

1.  Write down five general theories or statements which have been established by inductive reasoning.

2.  Is there any certainty that they will stand unchanged forever?

3.  Under what circumstances are such changes made?

4.  Can you cite any accepted laws or theories of past periods which have been overturned?

Deductive Reasoning.  After general laws have been established, either by human experience or accepted inductive reasoning, they may be cited as applying to any particular case under consideration.  This passing from the general law to the particular instance is deductive reasoning.  Deductive reasoning has a regular form called the syllogism.

Major premise.  All men are mortal. 
Minor premise.  Socrates is a man. 
Conclusion.  Therefore, Socrates is mortal.

If the three parts of a syllogism are correct it has absolute convincing power.  Most attempts to disprove its statement attack the first two statements.  Although it carries such an air of certainty it is likely to many errors in use.  An error like this is common: 

All horses are animals. 
All cows are animals. 
Therefore, all cows are horses.

Explain the fallacy in this syllogism.

Quite as frequently the incorrect syllogism is of this kind.

The edge of a stream is a bank. 
A bank is a financial institution. 
Therefore, the edge of a stream is a financial institution.

You will comment upon this that its evident silliness would prevent any speaker from using such a form in serious argument.  But recall that in the discussion of any idea a term may get its meaning slightly changed.  In that slight change of meaning lurks the error illustrated here, ready to lead to false reasoning and weakening of the argument.  Certain words of common use are likely to such shifting meanings—­republic, equality, representative, monarchy, socialistic.  Any doubtful passage in which such an error is suspected should be reduced to its syllogistic form to be tested for accuracy.