The fourth principle of being which occult science attributes to man is one which he does not share in common with the rest of the manifested world. It is that which differentiates him from his fellow creatures and makes him the crown of creation. Occult science helps in forming a conception of this further principle of human nature by pointing out the existence of an essential difference between the kinds of experience in waking life. On the one hand, man is constantly subjected to experiences which must of necessity come and go; on the other, he has experiences with which this is not the case. This fact comes out with special force if human experiences are compared with those of animals. An animal experiences the influences of the outer world with great regularity; under the influence of heat and cold it becomes conscious of pain or pleasure, and during certain regularly recurring bodily processes it feels hunger and thirst. The sum total of man’s life is not exhausted by such experiences; he is able to develop desires and wishes which go beyond these things. In the case of an animal it would always be possible, on going far enough into the matter, to ascertain the cause—either within or without its body—which impelled it to any given act or feeling. This is by no means the case with man. He may engender wishes and desires for which no adequate cause exists either inside or outside of his body. A particular source must be found for everything in this domain; and according to occult science this source is to be found in the human “I” or “ego.” Therefore the ego will be spoken of as the fourth principle of the human being. Were the astral body left to its own resources, feelings of pleasure and pain, and sensations of hunger and thirst, would take place within it, but there would be lacking the consciousness of something lasting in all these feelings. It is not the permanent as such, which is here designated the “ego,” but rather that which experiences this permanent element. In this domain, conceptions must be very exactly expressed if misunderstandings are not to arise. With the becoming aware of something permanent, lasting, within the changing inner experiences, begins the dawn of “ego consciousness.” The sensation of hunger, for instance, cannot give a creature the feeling of having an ego. Hunger sets in when the recurring causes make themselves felt in the being concerned, which then devours its food just because these recurring conditions are present. For the ego-consciousness to arise, there must not only be these recurring conditions, urging the being to take food, but there must have been pleasure derived from previous satisfaction of hunger, and the consciousness of the pleasure must have remained, so that not only the present experience of hunger but the past experience of pleasure urges the being to take nourishment.