The teacher, under this system, is the scientific, observing supervisor of this mental “playground” where the children acquire intellectual vigor, independence, and initiative as spontaneously, joyfully, and tirelessly as they acquire physical independence and vigor as a by-product of physical play. We have long realized that children do not need to be driven by force, or even persuaded, to take the amount of exercise necessary to develop their growing bodies. Indeed the difficulty has been to keep them from doing it so continuously as to interfere with our sedentary adult occupations and tastes. We have learned that all we need to do is to provide the jumping-rope and then leave the child alone with other children. The most passionately inspired pedagogue can never learn to skip rope for a child, any more than in after years he can ever learn the conjugation of a single irregular verb for a pupil. The learner must do his own learning, and, this granted, it follows naturally that the less he is interfered with by arbitrary restraint and vexatious, unnecessary rules, the more quickly and easily he will learn. An observation of the typical, joyfully busy child in a Casa dei Bambini furnishes more than sufficient proof that he enjoys acquiring mental as well as physical agility and strength, and asks nothing better than a fair and unhindered chance at this undertaking.
But even when this deep-laid foundation principle of self-education has been grasped, all is not plain sailing for the adventurer on the Montessori ocean. A set of theories relating to such complicated organisms as human beings, cannot in the nature of things be of primer-like simplicity. For my own convenience I very soon made two main divisions of the different branches on which the Montessori system is developed out of its central main idea. One division, the practical, is made up of theories based on acute, scientific knowledge of the child’s body, his muscles, brain, and nerves, such as only a doctor and a physiological psychologist combined can have. The second division is made up of theories based on the spiritual nature of man, as disclosed by the study of history, by unbiased direct observation of present-day society, and by that divining fervor of enthusiastic reverence for the element of perfectibility in human nature which has always characterized founders of new religions.