But the method of the reception and the character of the appropriation is constantly varying with the increasing collection of presentations or ideas already in the mind. The facility and completeness with which each fresh idea is assimilated is determined by what has gone before. Herein, according to the Herbartian school, lies the importance of directing the process of apperception by judicious selection of the materials which are to constitute the experience of the child. As the mind, in this view is simply built up entirely out of the ideas which it has received, the kinds of ideas presented to it and the order in which they come are of the utmost moment in the work of education. In the pleasure of the process of apperception lies the great fact of interest.
Interest depends on what is already in the mind.
Interest and knowledge react on each other. Interest stimulates voluntary attention and sustains involuntary. It thus ties at the root of the mental activity of observation. It determines what we shall see and also what we shall desire and will. Ignorance is really the main factor in vice.