Interest and discipline are correlative aspects, of activity having an aim. Interest means that one is identified with the objects which define the activity and which furnish the means and obstacles to its realization. Any activity with an aim implies a distinction between an earlier incomplete phase and later completing phase; it implies also intermediate steps. To have an interest is to take things as entering into such a continuously developing situation, instead of taking them in isolation. The time difference between the given incomplete state of affairs and the desired fulfillment exacts effort in transformation; it demands continuity of attention and endurance. This attitude is what is practically meant by will. Discipline or development of power of continuous attention is its fruit.

The significance of this doctrine for the theory of education is twofold. On the one hand it protects us from the notion that mind and mental states are something complete in themselves, which then happen to be applied to some ready-made objects and topics so that knowledge results. It shows that mind and intelligent or purposeful engagement in a course of action into which things enter are identical. Hence to develop and train mind is to provide an environment which induces such activity. On the other side, it protects us from the notion that subject matter on its side is something isolated and independent. It shows that subject matter of learning is identical with all the objects, ideas, and principles which enter as resources or obstacles into the continuous intentional pursuit of a course of action. The developing course of action, whose end and conditions are perceived, is the unity which holds together what are often divided into an independent mind on one side and an independent world of objects and facts on the other.