First, there is the pronounced difference between healthy minds and diseased minds.

The differences are so great that we have to pursue practically different methods of treating the diseased, not only as a class apart from the well minds--putting such diseased persons into institutions--but also as differing from one another.
Just as the different forms of bodily disease teach us a great deal about the body--its degree of strength, its forms of organization and function, its limitations, its heredity, the inter-connection of its parts, etc .-- so mental diseases teach us much about the normal mind.
This gives another sphere of information which constitutes "Abnormal Psychology" or "Mental Pathology." [Illustration: PLATE I.] [Illustration: PLATE II.] There are also very striking variations between individuals even within normal life; well people are very different from one another.
All that is commonly meant by character or temperament as distinguishing one person from another is evidence of these differences.

But really to know all about mind we should see what its variations are, and endeavour to find out why the variations exist.
This gives, then, another topic, "Individual or Variational Psychology." This subject should also have notice in the story.
4.

Allied with this the demand is made upon the psychologist that he show to the teacher how to train the mind; how to secure its development in the individual most healthfully and productively, and with it all in a way to allow the variations of endowment which individuals show each to bear its ripest fruit.

This is "Educational or Pedagogical Psychology." 5.