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.
Connected with the insistence on the psychological agencies of apperception and interest is the Herbartian principle of correlation and the five formal steps of instruction. The former should, according to the school, govern the drawing up of the curriculum. The five formal steps prescribe the order and method of procedure in an ideal lesson. Prepare the mind for the reception of the new matter by repetition of questions which freshen the pupil's recollection of ideas related to the subject of the coming lesson. Next present the matter clearly, developing it in an orderly method.