The mind is one thing - a unit. All the various "faculties" act together constantly. One cannot remember what an oak tree looks like unless he has carefully observed an oak tree. He cannot imagine an oak tree unless he remembers it. He cannot judge of the difference between an oak tree and a maple tree unless he can imagine a picture of the two side by side. And he cannot do any one of these things without attention; nor again can he concentrate his attention without an act of will.
So we see that the various acts of the mind, perception, memory, imagination, judgment, attention, and will, are inextricably interdependent - and that one act involves all the rest.
Happily this makes our task all the easier and more interesting. In this series I shall begin by giving you some plain practical advice as to the development of the perceptive powers - the ability to see, hear, feel, taste, and smell more efficiently. But with every moment of practice such as I advise you will also be developing a more exact and acute memory, a finer and more expansive imagination, a greater power concentration, and a stronger will. When we come to discuss the cultivation of the will power the exercises will require the use of the perceptions, the memory, the imagination, and other faculties. So, you see, in developing the mind in any one phase of its activity you are, at the same time and by the same act, adding to the power and usefulness of the entire mind.