ry here, but it will be of value to consider
briefly three chief errors.

If the terms are not used with the same meaning throughout, the conclusion
is valueless. A person might agree with you that domestic arts should be
taught to girls in school, but if you continued by saying that scrubbing
the floor is a form of domestic art, therefore the girls should be taught
to scrub the floor, he would reject your conclusion because the meaning of
the term _domestic art_ as he understood it in the first statement, is not
that used in the second.

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.

3. I ought not to study algebra because it is a very difficult subject.

4. Pupils ought not to write notes because note writing interferes with
the rights of others.

5. All fish can swim;
Charles can swim;
Therefore Charles is a fish.

6. Henry is a fool because