300. Among the various masses of ideas (29) some necessarily acquire permanent predominance, others come and go. But if this relation reaches full development and becomes fixed too early, the controlling ideas no longer admit of being arrested to the extent necessary for the reception of the new material offered by instruction. This fact explains the experience that clever boys, notwithstanding the best intentions to receive instruction, yet frequently appear very unreceptive, and that a certain rigidity of mind, which in later manhood would not occasion surprise, seems to have strayed, as it were, into boyhood. No one should allow himself to be betrayed into encouraging such narrowness by commendatory terms such as pertain to strength and energy; just as little, however, should clumsy teaching and its sequel, listless learning, be left out of account, as having no bearing on this state of affairs. For, rather may it be assumed that the fault mentioned might have been largely forestalled by very early instruction of all kinds, provided such instruction had been combined with a variety of attractive rather than of too difficult tasks. Where, on the other hand, mental nervousness has once taken root, it cannot be eradicated by all the art and painstaking effort of a multitude of teachers. When the questions of a child, six years old let us say, give rise to the apprehension that they proceed from a too contracted mental horizon, there should be no delay about resorting to manifold forms of stimulation, especially in the way of widening the pupil’s experience to the greatest practicable extent. 301. On the other hand, it is not rare to find boys, and even young men, in whose minds no one thought-mass attains to any very prominent activity. Such boys are always open to every impression and ready for any change of thought. They are wont to chat pleasantly, and to form hasty attachments. Here belong those who learn easily and forget as quickly. This defect, too, when once confirmed, resists all skill and good intentions; strength of purpose, from the very nature of the case, is out of the question. The situation varies in gravity, however, according to the influences of the earliest environment. If these proved distracting, the fault mentioned assumes alarming proportions even in minds otherwise well endowed. But where some form or other of necessary respect has been steadily at work, the youth will raise himself to a higher plane than the boy gave promise of doing. Least of all, however, can the teacher allow himself to be betrayed into hoping for a future development of talent by superficial alertness, combined, it may be, with droll fancies, bold pranks, and the like. Talent reveals itself through persistent endeavor, sustained even under circumstances little favorable to it, and not until such endeavor clearly manifests itself is the thought of giving it support to be entertained.