It will be noticed that each syllogism includes three terms. For example, the syllogism,—
All hawks eat flesh;
This bird is a hawk;
Therefore this bird eats flesh,—
contains the three terms, hawk, eats flesh, this bird; of these but two appear in the conclusion. The one which does not (in this case hawk) is called the middle term. If the major premise does not make a statement about every member of the class denoted by the middle term, the conclusion may not be valid even though the premises are true. For example:—
All hawks are birds;
This chicken is a bird;
Therefore this chicken is a hawk.
In this case the middle term is birds, and the major premise, All hawks are birds, does not make a statement which applies to all birds. The conclusion is therefore untrue. Such an argument is a fallacy.
The validity of the conclusion is impaired if either premise is false. In the enthymeme, "Henry is a coward; he dare not run away from school," the suppressed premise, "All persons who will not run away from school, are cowards," is not true, and so invalidates the conclusion. It is well to test the validity of your own argument and that of your opponent by seeking for the suppressed premise and stating it, for this may reveal a fatal weakness in the thought.
EXERCISES
Which of the following are incorrect?
1. The government should pay for the education of its people;
Travel is a form of education;
Therefore the government should pay the traveling expenses of the
people.
2. All horses are useful;
This animal is useful;
Therefore this animal is a horse.