Thought is but the last come and least developed of its powers; one among its various responses to environment, and ways of laying hold on experience.
This conception of the multiplicity in unity of the psyche, conscious and unconscious, is probably one of the most important results of recent psychological advance.

It means that we cannot any longer in the good old way rule off bits or aspects of it, and call them intellect, soul, spirit, conscience and so forth; or, on the other hand, refer to our "lower" nature as if it were something separate from ourselves.

I am spirit when I pray, if I pray rightly.

I am my lower nature, when my thoughts and deeds are swayed by my primitive impulses and physical longings, declared or disguised.

I am most wholly myself when that impulsive nature and that craving spirit are welded into one, subject to the same emotional stimulus, directed to one goal.