Division.  One of these methods is by division.  A speaker may separate a topic or term into the parts which comprise it.  For instance, a scientist may have to list all the kinds of electricity; a Red Cross instructor may divide all bandages into their several kinds; an athletic coach may have to explain all the branches of sports in order to induce more candidates to appear for certain events; a banker may have to divide financial operations to make clear an advertising pamphlet soliciting new lines of business, such as drawing up of wills.

The ability to do this is a valuable mental accomplishment as well as an aid to speaking.  In dividing, care must be taken to make the separations according to one principle for any one class.  It would not result in clearness to divide all men according to height, and at the same time according to color.  This would result in confusion.  Divide according to height first, then divide the classes so formed according to color if needed—­as might be done in military formation.  Each group, then, must be distinctly marked off from all other groups.  In scientific and technical matters such division may be carried to the extreme limit of completeness.  Complete division is called classification.

Partition.  In non-scientific compositions such completeness is seldom necessary.  It might even defeat the purpose by being too involved, by including too many entries, and by becoming difficult to remember.  Speakers seldom have need of classification, but they often do have to make divisions for purposes of explanation.  This kind of grouping is called partition.  It goes only so far as is necessary for the purpose at the time.  It may stop anywhere short of being complete and scientifically exact.  All members of the large class not divided and listed are frequently lumped together under a last heading such as all others, miscellaneous, the rest, those not falling under our present examination.

EXERCISES

1.  Classify games.  Which principle will you use for your first main division—­indoor and outdoor games, or winter and summer games, or some other?

2.  Classify the races of men.  What principle would you use?

3.  How would you arrange the books in a private library?

4.  Classify the forms of theatrical entertainments.  Is your list complete?

5.  Classify branches of mathematics.  The entries may total over a hundred.

6.  Classify the pupils in your school.

7.  Classify the people in your school.  Is there any difference?

8.  Classify the following: 

The political parties of the country. 
Methods of transportation. 
Religions. 
Magazines. 
The buildings in a city. 
Aircraft. 
Desserts. 
Canned goods.

Skill in division is valuable not only as a method of exposition but it is linked closely with an effective method of proving to be explained in the next chapter—­the method of residues.  Can you recall any extracts given in this book in which some form of division is used?  Is this form of material likely to be more important in preparation or in the finished speech?  Explain your opinion—­in other words, present a specimen of exposition.