|The Stoics therefore emphasized a teaching which is entirely
in line with the Oriental philosophy. They bridged the gap therefore between the two
Plato expounded the doctrine of the soul in the following manner:
"He believed the soul to have three parts. One, an immortal or rational part,
coming from God; another a mortal, animal or sensitive part, the seat of appetite and
sensation, belonging to the body; and a third, lying between these and making their
interaction possible - will or spirit - by means of which reason conquered desire. Plants
have the lowest part; animals the two lower; but the rational part is exclusively human.
This rational soul he regarded as immaterial and metaphysical in nature, incapable of
being perceived by the senses, and only to be grasped by the intellect. The union with the
mortal, material and physical body was only a minor incident of its long career... Plato
thus drew a fundamental distinction between soul and body."
- Hollander, Bernard, M.D., In Search of the Soul, Vol. I, pp. 35.
Aristotle regarded the soul as the sum of the vital principles and as being to the body
what vision is to the eye. The soul was to him the true Being in the body, and with him
Plotinus was in agreement. He regarded the soul as the living sentiency of the body,
belonging to a higher degree of being than matter. Tertullian divided the soul into two
parts, a vital and a rational principle, as did St. Gregory. Most of the Oriental schools
regard  the soul as the self, the individual, and Christian mysticism is concerned
with the elaboration of the teaching of St. Paul, that there dwells in each human being a
potentiality which is called by him "Christ in you," and which, through its
presence, enables every man eventually to attain the status of the Christ. A close
comparison of the Christian and Oriental teachings leads to the conclusion that the terms:
Self, Soul, Christ, connote the same state of being or consciousness, and indicate the
subjective reality in every man.
Christian Fathers were tremendously influenced by Greek ideas as to the Soul, and their
teaching was later colored by Gnosticism and Manicheanism. By them the soul was regarded
as light and the body as darkness; light must irradiate the body and eventually be
liberated from the body. St. Gregory in the 4th century emphasized the triplicate of body,
soul and spirit as did St. Paul. He summed up in his teaching the point of view of the
best thinkers of his time, and (quoting Dr. Hollander) taught that:
has no parts, yet Gregory distinguished nutritive, sensitive, and rational faculties,
corresponding to the body, soul and spirit. The rational nature is not equally present in
all parts of the body. The higher nature uses the lower as its vehicle. In matter resides
the vital power; in the vital dwells sensitive power, and to the sensitive power is united
the rational. The sensitive soul is thus a medium, purer than flesh and grosser than the
rational soul. The soul thus  united with the body is the real source of all
- Hollander, Bernard, M.D., In Search of the Soul, Vol. I, p. 88.
5th century on to the 17th we have the ideas of various schools; of Scholastics, of
Arabian philosophers, of Kabalists, also the philosophers of the Middle Ages, and that
notable group of men who brought about the Reformation and Renaissance. They discussed the
various theories accounting for the soul, but not much progress was made, for all was
gradually tending towards the emergence of modern science, the establishment of modern
medicine, and the revelations of the age of electricity. Gradually the form aspect of
nature and the laws governing natural phenomena engrossed attention, until speculations as
to the soul and its nature were increasingly relegated to the theologians.
In the 17th century, Stahl wrote fully upon the subject of the soul and summarized a
great deal of the teaching extant in his time. This has been termed the Theory of Animism.
It is the doctrine that the soul is the vital principle, and responsible for all organic
development. We speak of the animism of the little evolved races, who personified and
worshipped the forces of nature; we recognize the animism outlined by Stahl in the later
cycles of our own time as having been always present; we study the modern scientists'
teaching as to force, as to energy, as to the atom, and we find that we are 
confronted by a world of energies which cannot be negated. We live in a universe animated
by forces. Speed, activity, vitality, transportation, the transmission of sound,
electrical energy, and many such phrases are the catch-words of today. We speak and think
in terms of force.
summed up the teaching in the following terms:
"The body is made for the soul; the soul is not made for, and is not the product
of, the body... The source of all vital movement is the soul, which builds up the machine
of the body, and maintains it for a time against external influences... The immediate
cause of death is not disease, but the direct action of the soul, which leaves the bodily
machine, either because it has become unworkable through some serious lesion or because it
does not choose to work it any longer."
- Hollander, Bernard, M.D., In Search of the Soul, Vol. I, p. 169.
Berkeley's definition of the soul is interesting, for he defines it as a simple, active
being, revealed to us through experience.
The modern materialistic psychology which regards the soul as the product of brain
activity is perhaps not entirely wrong but is dealing with a secondary demonstration of
the vital soul.
Dr. Müller-Freienfels says: "...we must not regard the body as an atomistic
mechanism but rather as the vehicle of a comprehensive vital energy; whereupon the 'body'
ceases to be merely matter and is conceived of as being 'animated'." 
He goes on to say also: "And now at last we see a possibility of arriving at a
conception of the soul! Let us remember how mankind came to form this conception. Not in
order to explain the 'consciousness' (for the 'soul' can exist without consciousness), but
in order to make comprehensible that complex continuity of activities which we call life,
mankind created the conception of the soul. We have already stressed the fact that in all
primitive cultures the 'soul' is by no means identical with the consciousness, and that
this equivalence is a late philosophical reservation. As a matter of fact, what primitive
man understands by 'soul' is what we today call 'life.' 'Animated' and 'alive' are, as
conceptions, completely identical, just as the conceptions 'inanimate' and 'dead' are
identical. The Greek word psyche does not by any means signify merely
consciousness, but can usually be translated simply by 'life,' and similarly, in many
cases the German words Leben and Seele, as the English words 'life' and
'soul,' are interchangeable...
In this, however, we are at one with both the main tendencies of recent philosophy.
Even the later materialists had come to admit that the soul is not a substance, but that
the psychical processes occur in substance, and they therefore regarded it as equivalent
to 'motion.' On the other hand, the conscientialists also regarded psychical processes as
'events' which they had somehow to bring into relation with physical movements.
We accept both these notions. What we call 'soul' is neither an extended 'substance'
nor a thinking 'substance'; it is not a 'substance' at all, but a highly complicated
event, a continuity of effects, which reveals itself on the one hand in the building up of
the body, and on the other in the consciousness. 
Nevertheless, this doctrine of ours, which does not divide the universe into substance
and consciousness, but places a connecting-link between the two, which on the one hand
reveals itself materially, but is also the hypothesis of the consciousness, differs from
both materialism and conscientialism in this, that it does not conceive of the soul as
existing in substance alone nor yet in consciousness alone. On the contrary, both
consciousness and body appear to us only as effect of a third thing which comprehends them
both, producing the consciousness and also giving form to the raw material. We have
already seen that the consciousness must necessarily demand such a profounder 'being,'
whereas the materialistic theory demands a formative 'power,' which forms the body and
with it the soul. One might call this theory 'monistic,' though it avoids one-sidedness
just as it avoids dualism, only that the conception has been overworked, and both the
consciential theory and the materialistic theory are - though, after all, incorrectly -
described as monistic. We call the theory towards which we are working the dynamistic
theory, because it represents the nature of the soul as directed force; and we may also
call it vitalistic, because this force, which gives the body form and engenders the
consciousness, proves to be identical with life."
- Müller-Freienfels, Richard, Mysteries of the Soul, pp. 40, 41, 42.