waking hours
these models for the physical body are not present in the astral body, or,
at least, only to a certain extent. For in waking life the soul replaces
these models with its own images. When a person directs his senses upon
his environment he thus creates in his ideas pictures which are copies of
the world around him. In fact these copies at first disturb the prototypes
which give the etheric body the impulse to preserve the physical body.
Such disturbance could not be present if a man, by virtue of his own
activity, could convey to his astral body those pictures which would give
the right impulse to the etheric body. Yet this very disturbance plays an
important part in human life, and is able to express itself because the
models for the etheric body do not come into full play in the waking life.
This fact is revealed by "fatigue." Now, during sleep, no external
impressions disturb the force of the astral body. Therefore in this
condition it can expel fatigue. The work of the astral body during sleep
consists in removing fatigue, and it can accomplish this only by leaving
the physical and etheric bodies. During waking life the astral body does
its work within the physical body; during sleep it works on the latter
from without.

For instance, just as the physical body has need of the outer world, which
is of like substance with itself, for its supply of food, something of the
same kind takes place in the case of the astral body. Let us imagine a
physical human body removed from the surrounding world: it would die. That
shows that physical life is an impossibility without the entire physical
environment. In fact, the whole earth must be just as it is if physical
human bodies are to exist upon it. For, in reality, the whole human body
is only a part of the earth,--indeed, in a wider sense, part of the whole
physical universe. In this respect it is related in the same sense as, for
example, the finger of a hand to the entire human body. Separate the
finger from the hand and it cannot remain a finger: it withers away. Such
would also be the fate of the human body were it removed from that body of
which it is a member,--from the conditions of life with which the earth
provides it. Let it be raised above the surface of the earth but a
sufficient number of miles and it will perish as the finger perishes when
cut off from the hand. If this fact is less apparent in the case of a
man's physical organism than in that of hi