--Mary Rogers Miller: _The Brook Book_.

(Copyright, 1902, Doubleday, Page and Co.)

+Theme XCIV.+--_Write an exposition on one of the following subjects, making use of particulars or details:_--

1. How ice cream is made.

2. The cultivation of rice.

3. Greek architecture.

4. How paper is made.

5. A tornado.

6. Description of a steam engine.

7. The circulatory system of a frog.

8. A western ranch.

9. Street furniture.

10. A street fair.

(Have you used particulars sufficient to make your meaning clear? Have you used any unnecessary particulars? Why is the arrangement of your topics easy in this theme?)

+169. Exposition by Cause and Effect.+--When our general statement is in the form of a cause or causes, the question naturally arises in our mind as to the effects resulting from those causes. In like manner, when the general statement takes the form of an effect, we want to know what the causes are that produce such an effect. From the very nature of exposition we may expect to find much of this kind of discourse relating to causes and effects. (See Section 49.)

Notice the following example:--

The effect of the polar whirls may be seen in the rapid rotation of water in a pan or bowl. The centrifugal force throws the water away from the center, where the surface becomes depressed, and piles it up around the sides, where the surface becomes elevated. The water being deeper at the sides than at the center, its pressure upon the bottom is proportionately greater. A similar effect is produced by the whirl of the air around the polar regions. It is thrown away from the polar regions and piled up around the circ.u.mference of the whirl. There is less air above the polar regions than above lat.i.tude 30-40, and the atmospheric pressure is correspondingly low at one place and high at the other. Thus the centrifugal force of the polar whirl makes the pressure low in spite of the low temperature. The position of the tropical belts of high pressure is a resultant of the high temperature of the equatorial regions on one side and the polar whirls on the other.

--Dryer: _Lessons in Physical Geography_.

+Theme XCV.+--_Write an expository theme using cause or effect._

Suggested subjects:--

1. The causes of the French Revolution.

2. How ravines are formed.

3. Irrigation.

4. Effects of smoking.

5. Lack of exercise.

6. Volcanic eruptions.

(Did you find it necessary to make use of any other method of explanation?

Did you make use of description in any place?)

SUMMARY

1. Exposition is that form of discourse the purpose of which is to explain.

2. The essential characteristics of an exposition are-- _a._ That it possess unity because it contains only those facts essential to its purpose.

_b._ That the facts used be arranged in a coherent order.

3. Exposition is concerned with (_a_) general terms or (_b_) general propositions.

4. The steps in the exposition of a term are-- _a._ Definition. This may be-- (1) By synonym (inexact).

(2) By use of the logical definition (exact).

_b._ Division. This may be-- (1) Complete (cla.s.sification).

(2) Incomplete (part.i.tion).

The same principle of division should be followed throughout.

5. Exposition of a proposition may use any one of the following methods-- _a._ By repet.i.tion.

_b._ By giving examples.

_c._ By stating comparisons and contrasts.

_d._ By making obverse statements.

_e._ By relating particulars or details.

_f._ By stating cause or effect.

_g._ By any suitable combination of these methods.

XI. ARGUMENT

+170. Difference between Argument and Exposition.+--Argument differs from exposition in its purpose. By exposition we endeavor to make clear the meaning of a proposition; by argument we attempt to prove its truth. If a person does not understand what we mean, we explain; if, after he does understand, he does not believe, we argue.

Often a simple explanation is sufficient to convince. As soon as the reader understands the real meaning of a proposition, he accepts our view of the case. A heated discussion may end with the statement, "Oh, if that is what you mean, I agree with you." In Section 70, we have learned that the first step in argument is explanation, by which we make clear the meaning of the proposition the truth of which we wish to establish.

This explanation may include both the expounding of the terms in the proposition and the explanation of the proposition as a whole.

There is another difference between exposition and argument. We cannot argue about single terms, though we may explain them. We may explain what is meant by the term _elective studies_, or _civil service;_ but an argument requires a proposition such as, Pupils should be allowed to choose their own studies, or, Civil Service should be established. Even with such a topic as Expansion or Restricted Immigration, which seems to be a subject of argument, there is really an implied proposition under discussion; as, The United States should acquire control of territory outside of its present boundaries; or, It should be the policy of our government to restrict immigration. We may explain the meaning of single terms or of propositions, but in order to argue, we must have a proposition either expressed or implied.

+171. Proposition of Fact and Proposition of Theory.+--Some propositions state facts and some propositions state theories. Every argument therefore aims either to prove the occurrence of a fact or the truth of a theory.

The first would attempt to show the actual or probable truth of a specific proposition; for example:--

Nero was guilty of burning Rome.

Joan of Arc was burned at the stake.

Barbara Frietchie actually existed.

Sheridan never made the ride from Winchester.

Homer was born at Chios.

The second would try to establish the probable truth of a general theory; for example:--

A college education is a profitable investment.

Light is caused by a wave motion of ether.