Even though the astral body during sleep passes through no experiences, though it is not conscious of pleasure, pain, and the like, it does not remain inactive. On the contrary, it is a fact that active work is its function in the sleep state. For it is the astral body which strengthens and recuperates man’s forces, exhausted during waking life. As long as the astral body is united with the physical and etheric bodies it is related to the outer world through these two bodies. They convey to it perceptions and representations. Through the impressions which they receive from their surroundings, it experiences pleasure and pain. Now the physical body can be preserved in the form and shape suitable to the individual only by means of the human etheric body. But this human form can be preserved only by an etheric body which on its part receives corresponding forces from the astral body. The etheric body is the builder, the architect, of the physical body. It can, however, construct in the true sense only when it receives from the astral body the impulse as to the manner in which it must build. In this latter are contained the models, according to which the etheric body gives the physical body its form. During our 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.