In the same way, knowledge derived from earlier lessons must be extended and deepened by subsequent instruction. This presupposes such an organization of the whole work of instruction that that which comes later shall always find present the earlier knowledge with which it is to be united. 79. Ordinarily, because their eyes are fixed solely on the facts to be learned, teachers concern themselves little with the ideas already possessed by the pupils. Consequently they make an effort in behalf of the necessary attention only when it is failing and progress is checked. Now they have recourse to voluntary attention (73), and to obtain this rely on inducements, or, more often, on reprimands and penalties. Indirect interest is thus substituted for direct interest, with the result that the resolution of the pupil to be attentive fails to effect energetic apprehension and realizes but little coherence. It wavers constantly, and often enough gives way to disgust. In the most favorable case, if instruction is thorough, _i.e._, scientific, a foundation of elementary knowledge is gradually laid sufficiently solid for later years to build on; in other words, out of the elementary knowledge an apperceiving mass is created in the mind of the pupil which will aid him in his future studies. There may be several of such masses; but each constitutes by itself its own kind of one-sided learning, and it is after all doubtful whether even here direct interest is implied. For there is small hope that this interest will be aroused in the youth when the years of boyhood have been devoted merely to the mastering of preliminary knowledge. The prospects of future station and calling are opening before him and the examinations are at hand. 80. The fact should not be overlooked, however, that even the best method cannot secure an adequate degree of apperceiving attention (75–78) from every pupil; recourse must accordingly be had to the voluntary attention, _i.e._, the pupil’s resolution. But for the necessary measures the teacher must depend, not merely on rewards and punishments, but chiefly on habit and custom. Instruction unites at this point with government and training. In all cases where the pupil begins his work not entirely without compulsion, it is particularly important that he should soon become aware of his own progress. The several steps must be distinctly and suitably pointed out to him; they must at the same time be easy of execution and succeed each other slowly. The instruction should be given with accuracy, even strictness, seriousness, and patience.