It is evident that some _external_ basis is necessary in the progressive development of such phenomena, and that the teacher, who is to respond to the requests of the child in conscious evolution, cannot do so adequately by haphazard means; he must be guided by conditions previously determined by experience. In other words, those external means already alluded to several times, that _staircase_, the steps of which lead the soul upwards, must have been already _established by experience_, just as all the preceding means of the first development of the infant were established. The construction of the ascending stairway, of the external means of support for the soul in process of evolution, is gradually amplified, like an inverted cone, the apex of which touches the very beginnings of psychical life, resting upon that primitive impulse which attracts the child of two and a half to the sensory stimuli, just as hunger leads the new-born infant to perform the wonderful complex action of sucking. And as these external means multiply, they are complicated more and more by the growing psychical needs of the child, and comprise within themselves the principles of culture. The highest external organization is not based solely upon psychological necessities, but also upon those factors which take into account the cultural aspect itself. Each subject of study, as, for instance, arithmetic, grammar, geometry, natural science, music, literature, should be presented by means of external objects upon a well-defined systematic plan. The essentially psychological character of the preliminary work must now be supplemented by the collaboration of specialists in each subject, in order to ensure the establishment of that aggregate of means necessary and sufficient to incite to auto-education. This is the experimental preparatory work, which establishes those means of development, those external _impressions_, necessary to unfold the inner life, and an _exact_ correspondence to the psychical needs of _formation_ is essential in their construction. Up to a certain point, they might correspond with the so-called didactic or objective material of the old methods. Their significance, however, is profoundly different. The objective material of the old schools was an aid to the teacher, in making his explanations comprehensible to a collective class listening passively to him. The objects were related solely _to the things to be explained_, and these were chosen at random, that is to say, without any scientific criterion of their relation to the psychical needs of the child. Here, on the other hand, _the means of development_ are experimentally determined with reference to the psychical evolution of the child; and their aim is not to give mere instruction; they represent the means which induce a spontaneous interpretation of the internal energies.