It is easy to perceive, that the pleasure and happiness experienced by a child during his play, arise altogether from the _state of his mind_, to which the physical exercises and amusements only conduce. When this mental satisfaction is examined, we find it to consist chiefly of two elements,--that of active thought, and that of self-approbation. The first,--that of active thought, or the reiteration of ideas, we have before pointed out and explained, as it is illustrated in their play, and in the pleasure they take in hearing stories, reading riddles, dressing dolls, and similar acts; and it is only here necessary to add, that their desire of congregating together for amusement has its origin in a similar cause. New ideas stimulate more powerfully to active thought; and children soon find, and insensibly draw the lesson, that the aggregate of new ideas is always enlarged by an increase of the number of persons who supply them. Two children will play with the same number of toys for a longer time, without tiring, than if they were alone;--and three or four would, in the same proportion, increase the interest and prolong the season of activity. But as soon as the reiteration of the ideas suggested by their game becomes languid or difficult, their play for the time loses its charms, and the fascination is gone. That it is the cessation of active thought, which is the chief cause of their play ceasing to please, is proved from the circumstance, that if another interesting companion shall be added to their number, or if any thing shall occur to renew this operation,--the reiteration of ideas,--upon the mind, the same degree of interest, and to a corresponding extent, is immediately felt, and the play is resumed. Now, the catechetical exercise is in reality the same operation in another form. The questions of the teacher excite the pupil to the same kind of active thought as that which gives relish to his play; and, while the teacher confines himself within the limits of the announcement, the mental excitement is active, but moderate, and always successful.