The development of the intellect depends in so great measure upon the modification of innate endowments through natural environment and education, even before systematic instruction begins, and the methods of education are so manifold, that it is at present impossible to make a complete exposition of a normal intellectual development. Such an exposition would necessarily comprise in the main two stages: 1. The _combination_ of sensuous _impressions_ into _perceptions_ (Wahrnehmungen); which consists essentially in this--that the sensation, impressing itself directly upon our experience, is by the intellect, now beginning to act, co-ordinated in space and time. 2. The _combination_ of _perceptions_ into _ideas_; in particular into _sense-intuitions_ and _concepts_. A sense-intuition (Anschauung) is a perception together with its cause, the object of the sensation; a concept (Begriff) results from the union of the previously separated perceptions, which are then called separate marks or qualities. The investigation of each of these stages in the child is in itself a great labor, which an individual may indeed begin upon, but can not easily carry through uniformly in all directions. I have indeed tried to collect recorded facts, but have found only very little trustworthy material, and accordingly I confine myself essentially to my own observations on my child. These are not merely perfectly trustworthy, even to the minutest details (I have left out everything of a doubtful character), but they are the most circumstantial ever published in regard to the intellectual development of a child. But I have been acquainted with a sufficient number of other children to be certain that the child observed by me did not _essentially_ differ from other healthy and intelligent boys in regard to the principal points, although the time at which development takes place, and the rapidity of it, differ a good deal in different individuals. Girls often appear to learn to speak earlier than boys; but further on they seem to possess a somewhat inferior capacity of development of the logical functions, or to accomplish with less ease abstractions of a higher order; whereas in boys the emotional functions, however lasting their reactions, are not so delicately graduated as in girls. Without regard to such differences, of which I am fully aware, the following chapters treat exclusively of the development of purely intellectual cerebral activity in both sexes during the first years. I acknowledge, however, that I have found the investigation of the influence of the affectional movements, or emotions, upon the development of the intellect in the child during the first years so difficult, that I do not for the present enter into details concerning it. The observations relate, first, to the non-dependence of the child's intellect upon language; next, to the acquirement of speech; lastly, to the development of the feeling of self, the "I"-feeling. CHAPTER XVI.