In practice the words which most often need definition are those which are, as it were, shorthand symbols for perhaps a very extensive meaning. Unless the limits of this extended meaning are clearly marked out you cannot tell whether the minds of your readers are, as the lawyers say, running on all fours with your own or not. This extended meaning may be of various sorts: for example, it may be a large general principle, as in the case of "evolution" or "culture"; or it may be a general system or practice, as in the case of "commission government," "honor system," or "high standards for graduation"; or it may be a general class of things, persons, or events, as in the case of "secondary school," "professional coach," or "murder." When you use any such term in an argument, it is essential that your readers shall have the same set of details, ramifications, or instances in mind as you have yourself. For this purpose you must define the term; or, in other words, you must lay out or display the ramifications and limitations of the principle, the details of the system or practice, or the exact kinds of things, persons, or events, which you have in mind when you use the term. A few examples will make this practical meaning of defining clear.
Sometimes the definition proceeds by careful and specific limitation of the general signification of a word, as in the following example from Bagchot:
I should say that except where it is explained to the contrary, I use the word "toleration" to mean toleration by law. Toleration by society of matters not subject to legal penalty is a kindred subject, on which if I have room I will add a few words; but in the main I propose to deal with the simpler subject, toleration by law. And by toleration, too, I mean, when it is not otherwise said, toleration in the public expression of opinions; toleration of acts and practices is another allied subject, on which I can, in a paper like this, but barely hope to indicate what seems to me to be the truth, and I should add that I deal only with the discussion of impersonal doctrines: the law of libel, which deals with accusations of living persons, is a topic requiring consideration by itself.9
Sometimes the definition is rather an unfolding and displaying of the implications (from the Latin, implicare, to fold in) of the term. Huxley, near the beginning of his three "Lectures on Evolution," made sure by the following definition that his hearers should have a precise idea of what he meant by the term "evolution":
The third hypothesis, or the hypothesis of evolution, supposes that, at any comparatively late period of past time, our imaginary spectator would meet with a state of things very similar to that which now obtains; but that the likeness of the past to the present would gradually become less and less, in proportion to the remoteness of his period of observation from the present day; that the existing distribution of mountains and plains, of rivers and seas, would show itself to be the product of a slow process of natural change operating upon more and more widely different antecedent conditions of the mineral framework of the earth; until, at length, in place of that framework, he would behold only a vast nebulous mass, representing the constituents of the sun and of the planetary bodies. Preceding the forms of life which now exist our observer would see animals and plants not identical with them, but like them; increasing their differences with their antiquity and, at the same time, becoming simpler and simpler; until, finally, the world of life would present nothing but that undifferentiated protoplasmic matter, which, so far as our present knowledge goes, is the common foundation of all vital activity.
The hypothesis of evolution supposes that in all this vast progression there would be no breach of continuity, no point at which we could say, "This is a natural process," and "This is not a natural process," but that the whole might be compared to that wonderful process of development which may be seen going on every day under our eyes, in virtue of which there arises, out of the semifluid, comparatively homogeneous substance which we call an egg, the complicated organization of one of the higher animals. That, in a few words, is what is meant by the hypothesis of evolution.10
Here Huxley has laid out, in compact form the principal ramifications of the great principle of evolution, giving his hearers something like an outline map of it with its limits and principal divisions.
Where you have a practice or system to define, you will be more likely to do it by specifying the chief and essential details of the system, as in the following definition of commission government for cities. It will be noticed that this narrows down the meaning of the term to something like the Des Moines system, as distinguished from the Galveston plan.
A straight commission form of municipal government, in the judgment of Dr. Charles W. Eliot, one of its most active advocates, requires a commission composed of five members elected at large, one of whom is called the mayor, acting as chairman of the commission, but with no veto power, or any other special power not shared by the other members of the commission. The commission so elected is the source of all authority in the city, makes all ordinances, appoints all officials, collects taxes, and makes all appropriations. As set forth by its advocates, the significant features of the plan, in addition to those already mentioned, are:
Assignment of the important divisions of the city government to individual members of the commission, or their election thereto by the voters, each being directly responsible for the conduct of his particular department; adequate compensation to the commissioners for their time and labor, the city employing all the commissioners at living salaries, thus elevating the dignity of municipal service and making it a public career, and not a mere avocation; regularity, frequency, and publicity of the meetings of the commissioners; all employees above the class of day laborers selected from eligible lists based on examinations, oral and written, carefully devised to develop merit and fitness; recommendations after examination by an independent civil service commission; provision for the retention in office of all employees so appointed during good behavior; the power to initiate legislation reserved to the people, this right being known as the initiative; the power to call for a public vote on any measure adopted by the commission before being given effect as law reserved to the people, this being known as the referendum; the power at any time to make any member of the commission stand for reelection reserved to the people, this being known as the recall; the granting of public franchise always to be submitted to the approval of the electors.
There are two other important features: the introduction of the principle of the short ballot and the elimination of ward lines. In the matured judgment of municipal students these are considered, together with the concentration of authority, as the most effective features of the system.11
Here is a pretty complete display of all the essential details of the system which the author of this definition intended to mean by the term "commission government for cities."
Where the term which is to be defined is the name of a general class, whether of persons, things, or events, the definition must show just what persons, things, or events are to be included under the term for the present purpose. Lincoln gave a famous example of this sort of definition in the opening of his address at Cooper Institute, February 27, 1860. He took for the text of the first part of his speech a statement of Senator Douglas.
In his speech last autumn at Columbus, Ohio, as reported in the New York Times, Senator Douglas said, "Our fathers, when they framed the government under which we live, understood this question just as well, and even better, than we do now."
I fully indorse this, and I adopt it as a text for this discourse. I so adopt it because it furnishes a precise and an agreed starting point for a discussion between Republicans and that wing of the Democracy headed by Senator Douglas.