49.  The Brief and the Argument.  If your brief is thoroughly worked out, and based on a careful canvass of the evidence, the work on your argument ought to be at least two thirds over.  The last third, however, is not to be slighted, for on it will largely depend your practical results in moving your readers.  Even a legal argument rarely goes to the court on a written brief alone; and the average reader will never put himself to the effort of reading through and grasping such a brief as we have been planning here.  Furthermore, if your complete argument is merely a copying out of the brief into consecutive sentences and paragraphs, you will get few readers.  The making of the brief merely completes what may be called the architectural part of your labors; the writing of an argument will use all the skill you have in the choice of words and putting them together.

We saw in Chapter I that argument has two kinds of appeal to its reader:  on the one hand, through its power of convincing it appeals to his reason; on the other, through its persuasive power it appeals to his feelings and his moral and practical interests.  Of these two kinds of appeal the convincing power is largely determined by the thoroughness of the analysis and the efficiency of the arrangement, and therefore in large part hangs on the work done in making the brief; the persuasive power, on the other hand, though in part dependent on the line of attack laid out in the brief and the choice of points to argue, is far more dependent on the filling in of the argument in the finished form.  Even the severest scientific argument, however, is much more than the bare summary of the line of thought which would be found in a brief; and in an argument like the speeches in most political campaigns a brief of the thought would leave out most of the argument.  Wherever you have to stir men up to do things you have only begun when you have convinced their reason.

50.  The Introduction of the Argument.  Much depends on the first part of your argument, the introduction.  Its length varies greatly, and it may differ largely in other ways from the introduction to your brief.  If the people you are trying to convince are familiar with the subject, you will need little introduction; a brief but clear statement of fundamentals will serve the purpose.  For such an audience it is chiefly important to make the issues stand out, so that they shall see perfectly distinctly the exact points on which the question turns.  Then the sooner you are at work on the business of convincing them, the better.  In such arguments the introduction will perhaps not differ greatly in substance from the introduction to the brief, though it must be reduced to consecutive and agreeable form.  At the other extreme is such an argument as that of Huxley’s (p. 233), where he had to prepare the way very carefully lest the prejudice against a revolutionary and unfamiliar view of the animate world should close the minds of his hearers against him before he was really started.  Accordingly, before getting through with his introduction he expounded not only the three hypotheses between which the choice must be made, but also the law of the uniformity of nature and the principles and nature of circumstantial evidence.  Where one shall stop between these two extremes is a question to be decided in the individual argument.