EXERCISES
Select three of the following subjects and make lists of facts that you know about them. From these select those which would be necessary in making a clear explanation of each. After making out these lists of facts, arrange them in what seems to you the best possible order for making the explanation clear to your classmates.
1. The value of a school library. 2. Sponges. 3. The manufacture of clocks. 4. Drawing. 5. Athletics in the high school. 6. Examinations. 7. Debating societies.
+Theme LXXXVII.+—Following the outline, write an exposition on one of the subjects chosen.
(Notice the transition from one paragraph to another. See Section 87.)
+158. Exposition of Terms—Definition.+—Explanation of the meaning of general terms is one form of exposition (Section 63). The first step in the exposition of a term is the giving of a definition. This may be accomplished by the use of a synonym (Section 64). We make a term intelligible to the reader by the use of a synonym with which he is familiar; and though such a definition is inexact, it gives a rough idea of the meaning of the term in question, and so serves a useful purpose. If, however, we wish exactness, we shall need to make use of the logical definition.
+159. The Logical Definition.+—The logical definition sets exact limits to the meaning of a term. An exact definition must include all the members of a class indicated by the term defined, and it must exclude everything that does not belong to that class. A logical definition is composed of two parts. It first names the class to which the term to be defined belongs, and then it names the characteristic that distinguishes that term from all other members of the same class. The class is termed the genus, and the distinguishing characteristics of the different members of the class are termed the differentia. Notice the following division into genus and differentia.
TERM TO BE | CLASS | DISTINGUISHING
DEFINED | (Genus) | CHARACTERISTIC
| | (Differentia)
| |
A parallelogram | is a quadrilateral | whose opposite sides
| | are parallel
| |
Exposition | is that form of | which seeks to explain
| discourse | the meaning of a term.
| |
Each definition includes three elements: the term to be defined, the genus, and the differentia; but these are not necessarily arranged in the order named.