(2) _The Scholar._ One book must be studied closely by the teacher, and that is his pupils. During the last thirty years human nature in all its stages, as child, as youth, during adolescence, and in maturity--especially in the earlier periods--has been investigated as never before. The student in our time can enter into the results of special study upon these subjects. He needs to know what the best books can give him of child study and mind study; and to supplement book-knowledge in this department with watchful eyes and close thought upon the traits which he finds in his own scholars. (3) _The School._ The teacher in the Sunday school needs to understand the institution wherein he is a worker. The Sunday school is like the week-day school, yet unlike it; and the teacher must be able to appreciate at once what he can follow and what he should avoid in the methods of the secular school. The history of the Sunday-school movement, its fundamental principles, its organization, officers, methods of management, and aims--all these are in the scope of the teacher's preparation. (4) _The Work._ Whether on Sunday or on Monday, a teacher is after all a teacher, and the laws of true teaching are the same in a Sunday school, in a public school, and in a college. The application of those laws may vary according to the ages of pupils, the subjects of instruction, and the aims of the institution, but the principles are unchanging. Those enduring principles of instruction are well understood, are set down in text-books, and can easily be learned by a student. There are successful teachers who know these principles by an intuition that they cannot explain; but most people will save themselves from many mistakes and comparative failure by a close study of modern educational methods. In some way knowledge in all these four great departments of training should be obtained by the teacher, if possible, before he enters upon his task; but if he has missed earlier opportunities of preparation he must acquire this knowledge even while he is teaching. The outlines of such a course of study should be given in the training class for young people; and such a training class should be regarded as essential to every well-organized school.[11] 2. =The Teacher's Task.= All the preparation briefly outlined in these last paragraphs is only preparatory to the work which the teacher is to do in his vocation. The task set before the teacher is fourfold: