III. EXPLANATION OF COMPLEX IDEA

III. EXPLANATION OF COMPLEX IDEA
Useful though definitions be in communicating exact thought, there are many cases in which we need more than a mere definition in a single sentence to make our meaning clear. We may wish to explain a technical term, some complicated instrument, some more or less intricate process; and a fuller statement will be necessary. It will be useful to consider some¬what carefully the kinds of cases that may arise, and how to deal with each.
34. Explanation by Analysis.—Very often we have something to explain which the reader cannot per¬fectly understand until he knows the parts or steps of which it is made up. It may be a machine, it may
be the rig of a boat, it may be some process, like a triple play in baseball, or the making of a pudding— anything, in fact, that must be explained in detail in order that the whole may be clear. In this sort of explanation we can see at once that it is very impor¬tant that we find some principle which shall guide us in choosing the order of taking up the details. And if we think a moment, two 'methods will readily sug¬gest themselves: the method of choosing the impor¬tant details first and then showing the relation of the lesser ones to these; and the method of taking up the details one by one in a continuous series. Which method we shall employ depends, of course, largely on what we have to explain. Let us consider these methods separately, with a concrete example of each.
1. Details in Logical Sequence.—We will say that we are attempting to explain the game of tennis to a friend from the mountains, who, it chances, is not familiar with the game. First we must show how the court is laid out and prepared for play. We ourselves see it, in our mind's eye, in its entirety, and the technical terms connected with it are familiar to us through long use. It requires something of an effort, therefore, to remember that we cannot take this knowledge for granted in our reader, but that we must construct the picture of the tennis-court in his mind systematically, so that he may understand not only the details separately, but their relation to each other. Furthermore, we must not make use of a technical term, however familiar to us, until we
are sure that the reader understands what it means. Remembering these things, we may proceed with our explanation, handling the details much as we should were we writing a description for accuracy.
The "court" on which tennis is played is a hard, level surface, on which a rectangle, seventy-eight feet by thirty- six, is marked off by broad white lines. Within this rect¬angle two similar lines extend from end to end parallel to the side lines, and four feet and a half from them-, thus enclosing a narrower or single court, used when there is only one player on each side. Connecting these inside lines, and perpendicular to them, are two more lines, called "service-lines." These lines are therefore parallel to the lines marking the ends of the outside rectangle, and each is eighteen feet from its respective end. The middle points of these lines are joined by the "half-court line," which runs, consequently, parallel to the side lines and divides the central part of the court into halves. Ample space should he left about the court, for the players to use when necessary; especially at either end, where a space fifteen feet beyond the ends of the court is not too much.
A net extends from side to side of the court, dividing it equally. At the side-posts to which it is attached it is three feet and a half high, but at the centre of the court it drops to a height of three feet. A broad white tape marks the top of the net.
The rackets with which the game is played are wooden frames about ten inches in diameter, strung with a network of taut catgut strings at half-inch intervals. The handle at one end is about fifteen inches long. Light rubber balls are used, about two inches and a half in diameter and cov¬ered with a white cloth resembling felt.
The reasons for this order are perhaps fairly evident. The lines marking the outside limits of the court are easy to visualize. With reference to these we can
explain the position and direction of the lines marking off smaller divisions within the court. When the marking of the court has been made clear, it is natural to explain how the net is hung. Then a brief de¬scription of the racket and balls, and this part of our explanation is finished.
2. Details in Time Sequence.—If now we are called upon to explain how the game of "singles" in tennis is played, we have to use details once more, but this time to arrange them in the time order, taking up the steps one by one as they occur.
The "server" stands behind the end, or "base-line," to the right of the middle as he faces the net. With his racket he "serves" the ball so that it shall go over the net and fall within the smaller rectangular area next to the net and diagonally opposite to him. If the server fails thus to serve the ball—that is, if the ball fails to go over the net, or if it falls outside the limits indicated above—he has opportunity to serve a second ball. Should he fail to serve the second ball aright, he is said to have served "two faults," and a point in the score is credited to his opponent. The opponent, or "striker-out" as he is called, stands on the opposite side of the net, behind the area into which the ball must fall. When a ball is served without fault, he must "return" it; that is, striking it on its first bounce, he must drive it over the net so that it will fall within the limits of the "single" court. If for any reason he fails to do this, the server scores a point. If, however, he succeeds, the server must in his turn send the ball back, fulfilling the same conditions, with the exception that when the ball has once been put in play by being "served" and "returned" once, a player may, if he chooses, strike the ball before it touches the ground. Whoever fails to return the ball properly loses the point. The server then serves again, this time from the left side of the "base-line," so that the ball falls into the other
receiving court. The play ends, as before, when two faults are made in serving, or one player fails to return the ball as required by the conditions already explained. Each time a new play begins, the server changes his position from one side of the base-line to the other, serving alternately to the right and left receiving courts. When four points have been scored for one of the players the game is his, unless the game stands three points to three. It is then necessary to play until one player has made two points in addition to the total number made by his opponent, where¬upon the game is credited to him
The striker-out of the first game serves in the second game, and so the players alternate until one has won six games, constituting a "set." But if the games stand "five all," they must be continued until one player has won two games in addition to the total number made by his op¬ponent.
The order in this case is, of course, the order in which the events happen, and is already determined for us. It remains for us, however, to keep clear in the reader's mind just what the conditions are at each point in the process, so that the reader may readily follow the next step—a task that taxes all our power to think clearly and see through our reader's eyes as well as our own. It will be noticed that since we are explaining the process of playing, and not the arrangement of the court, we can assume knowledge of this latter subject, and need to explain only those terms that relate to the playing itself, "serving," "returning," and so on.
35. Explanation by Diagrams.—If our subject is an intricately contrived piece of mechanism, it is helpful to assist the reader by means of a diagram, clearly
drawn and lettered, as in the case of a proposition in geometry. This method often saves much minute and elaborate explanation, but it does not relieve us from the necessity of showing, in a clear, orderly manner, exactly what the drawing purports to repre¬sent, and what point of view the reader is intended to assume. If two or more diagrams are used, equal care, manifestly, must be taken to make each one clear.
36. Explanation by Examples, etc.—Another method of explanation peculiarly suited to a certain kind of subject is to select a typical example or illustration and let it stand for the whole of the class it represents. We are asked, for instance, to explain what an "idiom" is. We might define it as a use of words peculiar to the language in which it is found. But that is not enough. To make it clear we should give an example typical of idioms as a whole. We might go on to point out, then, that we in English ask "What time is it?" when the German would say "How much clock is it?" and the Frenchman would inquire "What hour is it?" Each form of words has become traditional in the language in which it is used, and is sanctioned rather by its actual use than by its logic.
Other devices there are—too many to try to explain in full—which can be of much practical assistance to us in solving the various problems to which we may set our hand. Each new subject will suggest its appropriate method if only we keep our minds alert. An explanation of "socialism," for example, would practically necessitate our contrasting the thing that
it is with "anarchy," the thing that it is not. An "earthquake" would naturally be explained as an effect, to be understood only when its cause had been made clear. Should our explanation approach the limits of description, as would be the case in a subject like the disposition of troops in a battle, it would be natural to compare the formation, inexactly per¬haps, to some simple figure or geometrical design. On occasion, too, we should be ready to combine two methods in explaining a single term. Were our sub¬ject the "safety-valve" of an engine, for example, we should be likely to show first what its parts are, explaining their relation to one another, and then how it works, taking up the several steps of its action in order of time.
These are but a few suggestions, but they will suffice. They are useful in so far as they are applied with sound, independent judgment. No more per¬tinent bit of advice can go with them than that which has already been given: Think always of the subject, not as you sec and understand it in itself, but as the reader will see it in your written words. The clear¬ness of the impression that he gets is the measure of your success.