Just as food is supplied to the physical body from its surroundings, so are the pictures of the world surrounding the astral body presented to it during the state of sleep. There, indeed, it lives in the universe, beyond the physical and etheric bodies: in that same universe out of which the whole man is born. The source of the images by means of which man receives his form is in this universe. He is linked in harmony with it; and when he awakens he rises above the surface of this all-pervading harmony to attain external perception. In sleep his astral body returns to the universal harmony. He brings so much strength from it to his bodies on awaking that he can once more dispense for a time with sojourning in the realm of harmony. The astral body returns during sleep to its home, and, on awaking, brings back into life freshly invigorated forces. That which the astral body thus gains, and brings with it on waking, finds its outer expression in the refreshment afforded by sound sleep. Further exposition of occult science will show that this home of the astral body is more extensive than that which belongs to the physical body in the narrower sense of the physical environment. Thus, while man as a physical being is a member of this earth, his astral body belongs to worlds in which other heavenly bodies besides our earth are included. During sleep, therefore,—(this can be made clear, as we have said, only by further explanations)—it enters a world to which other stars than the earth belong. In recognition of the fact that man lives during sleep in a world of stars, that is, in an astral world, occult science calls that principle of man which has its real home in that “astral” world and which, every time it returns to the sleep state, draws renewed force from that world, the _astral body_. It should be superfluous to point out that a misunderstanding might easily arise with regard to these facts; in our time, however, when certain materialistic modes of representation exist, it becomes quite necessary to draw attention to them. In quarters where such representation prevails it may, of course, be said that such a thing as fatigue can be scientifically investigated only in accordance with physical conditions. Even if the learned are not yet unanimous with regard to the physical cause of fatigue, one thing is quite firmly established; we must accept certain physical processes which lie at the root of this phenomenon. It would be well, however, if it were recognized that occult science does not in any way oppose this assertion. It admits everything that is said in this connection, just as it is admitted that for the physical erection of a house one brick must be laid upon another, and that when the house is finished its form and construction can be explained by purely mechanical laws. But the thought of the architect is necessary for the building of the house. This cannot be discovered merely by examination of physical laws.