-was anticipated by Plotinus, when he said in the Fourth Ennead,
that every soul has something of the lower life for the purposes of the
body and of the higher for the purposes of the Spirit, and yet
constitutes a unity; an unbroken series of ascending values and powers
of response, from the levels of merely physical and mainly unconscious
life to those of the self-determining and creative consciousness.[62] We
first discover psychic energy as undifferentiated directive power,
controlling response and adaption to environment; and as it develops,
ever increasing the complexity of its impulses and habits, yet never
abandoning anything of its past. Instinct represents the correspondence
of this life-force with mere nature, its effort as it were to keep its
footing and accomplish its destiny in the world of time. Spirit
represents this same life acting on highest levels, with most vivid
purpose; seeking and achieving correspondence with the eternal world,
and realities of the loftiest order yet discovered to be accessible to
us. We are compelled to use words of this kind; and the proceeding is
harmless enough so long as we remember that they are abstractions, and
that we have no real reason to suppose breaks in the life process which
extends from the infant's first craving for food and shelter to the
saint's craving for the knowledge of God. This urgent, craving life is
the dominant characteristic of the psyche. 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. When theologians and
psychologists, ignoring this unity of the self, set up arbitrary
divisions--and both classes are very fond of