The step of preparation has to do with making clear to the pupil the aim or purpose of the problem with which he is to deal. It is not always possible in the classroom to have children at work upon just such problems as may occur to them. The orderly development of a subject to be taught requires that the teacher discover to children problems or purposes which may result in thinking. The skill of the teacher depends upon his knowledge of the previous experiences of the children in the class and his skill in having them word the problem which remains unsolved in their experience in such a way as to make it attractive to them. Indeed, it may be said that children never have a worthy aim unless it is one which is intellectually stimulating. A problem exists only when we desire to find the answer. The term "presentation" suggests a method of procedure which we would not want to follow too frequently; that is, we may hope not simply to present facts for acceptance or rejection, but, rather, we want children to search for the data which they may need in solving their problem. From the very beginning of their school career children need, in the light of a problem stated, to learn to utilize all of the possible sources of information available. Their own experience, the questions which they may put to other people, observations which they may undertake with considerable care, books or other sources of information which they may consult, all are to be thought of as tools to be used or sources of information available for the solution of problems. It cannot be too often reiterated that it is not simply getting facts, reading books, performing experiments, which is significant, but, rather, which of these operations is conducted in the light of a problem clearly conceived by children. The step of presentation, as above described, is not one that may be begun and completed before other parts of the inductive lesson are carried on. As soon as any facts are available they are either accepted or rejected, as they may help in the solution of the problem; comparisons are instituted, the essential elements of likeness are noticed, and even a partial solution of the problem may be suggested in terms of a new generalization. The student may then begin to gather further facts, to pass through further steps of comparison, and to make still further modifications of his generalization as he proceeds in his work. At any stage of the process the student may stop to apply or test the validity of a generalization which has been formed. It is even true that the statement of the problem with which one starts may be modified in the light of new facts found, or new analyses instituted, or new elements of likeness which have been discovered.