It flows from the inherent nature of the subjects and of the learning mind. The repulsive processes of verbal memorizing, of discovering steps of mathematical identity, and the like, must borrow their interest at first from purely external sources, mainly from the personal interests with which success in mastering them is associated, such as gaining of rank, avoiding punishment, not being beaten by a difficulty and the like. Without such borrowed interest, the child could not attend to them at all. But in these processes what becomes interesting enough to be attended to is not thereby attended to _without effort_. Effort always has to go on, derived interest, for the most part, not awakening attention that is _easy_, however spontaneous it may now have to be called. The interest which the teacher, by his utmost skill, can lend to the subject, proves over and over again to be only an interest sufficient _to let loose the effort_. The teacher, therefore, need never concern himself about _inventing_ occasions where effort must be called into play. Let him still awaken whatever sources of interest in the subject he can by stirring up connections between it and the pupil's nature, whether in the line of theoretic curiosity, of personal interest, or of pugnacious impulse. The laws of mind will then bring enough pulses of effort into play to keep the pupil exercised in the direction of the subject. There is, in fact, no greater school of effort than the steady struggle to attend to immediately repulsive or difficult objects of thought which have grown to interest us through their association as means, with some remote ideal end. The Herbartian doctrine of interest ought not, therefore, in principle to be reproached with making pedagogy soft. If it do so, it is because it is unintelligently carried on. Do not, then, for the mere sake of discipline, command attention from your pupils in thundering tones. Do not too often beg it from them as a favor, nor claim it as a right, nor try habitually to excite it by preaching the importance of the subject. Sometimes, indeed, you must do these things; but, the more you have to do them, the less skilful teacher you will show yourself to be. Elicit interest from within, by the warmth with which you care for the topic yourself, and by following the laws I have laid down.