The soul works through the mechanism of the threefold personality. The method by which the soul and the personality vehicles interact and function together is presented in this volume; and also the way the human constitution, as a whole and in its component parts, responds to the impact of an evolving consciousness.

It is said that the aspirant to discipleship really needs to know only two things: the constitution of man and the next step ahead.  In this book the way the human constitution actually functions in its component parts is made abundantly clear.  It is an accepted goal for the aspirant that he learns to make of his personality equipment an instrument for the soul to use.