II. There must be data at command to supply the considerations required in dealing with the specific difficulty which has presented itself. Teachers following a "developing" method sometimes tell children to think things out for themselves as if they could spin them out of their own heads. The material of thinking is not thoughts, but actions, facts, events, and the relations of things. In other words, to think effectively one must have had, or now have, experiences which will furnish him resources for coping with the difficulty at hand. A difficulty is an indispensable stimulus to thinking, but not all difficulties call out thinking. Sometimes they overwhelm and submerge and discourage. The perplexing situation must be sufficiently like situations which have already been dealt with so that pupils will have some control of the meanings of handling it. A large part of the art of instruction lies in making the difficulty of new problems large enough to challenge thought, and small enough so that, in addition to the confusion naturally attending the novel elements, there shall be luminous familiar spots from which helpful suggestions may spring. In one sense, it is a matter of indifference by what psychological means the subject matter for reflection is provided. Memory, observation, reading, communication, are all avenues for supplying data. The relative proportion to be obtained from each is a matter of the specific features of the particular problem in hand. It is foolish to insist upon observation of objects presented to the senses if the student is so familiar with the objects that he could just as well recall the facts independently. It is possible to induce undue and crippling dependence upon sense-presentations. No one can carry around with him a museum of all the things whose properties will assist the conduct of thought. A well-trained mind is one that has a maximum of resources behind it, so to speak, and that is accustomed to go over its past experiences to see what they yield. On the other hand, a quality or relation of even a familiar object may previously have been passed over, and be just the fact that is helpful in dealing with the question. In this case direct observation is called for. The same principle applies to the use to be made of observation on one hand and of reading and "telling" on the other. Direct observation is naturally more vivid and vital. But it has its limitations; and in any case it is a necessary part of education that one should acquire the ability to supplement the narrowness of his immediately personal experiences by utilizing the experiences of others. Excessive reliance upon others for data (whether got from reading or listening) is to be depreciated. Most objectionable of all is the probability that others, the book or the teacher, will supply solutions ready-made, instead of giving material that the student has to adapt and apply to the question in hand for himself.