Theosophy, by Rudolf Steiner, , at sacred-texts.com
The soul being of man differs from his corporality through being his own inner world. This inner world peculiar to each person faces one the moment one directs one's attention to the simplest sensation. One finds, in the first place, that no one can know if another person perceives even the simplest sensation in exactly the same way as one does oneself. It is known that there are people who are colorblind. They see things only in different shades of gray. Others are partially colorblind. They are unable, because of this, to perceive certain shades of colors. The picture of the world which their eyes give them is different from that of so-called normal persons.
[paragraph continues] And the same holds good in regard to the other senses. It will be seen, therefore, without further elaboration, that even simple sensations belong to the inner world. I can perceive with my bodily senses the red table which another person also perceives; but I cannot perceive his sensation of red. One must therefore describe sensation as belonging to the soul. If one grasps this fact alone quite clearly, he will soon cease to regard inner experiences as mere brain processes or something similar. The first result of sensation is feeling. One sensation causes man pleasure, another displeasure. These are stirrings of his inner, his soul life. Man creates in his feelings a second world in addition to that which works on him from without. And a third is added to thisthe will. Through it man reacts on the outer world. And he thereby stamps the impress of his inner being on the outer world. The soul of man, as it were, flows outward in the activities of his will. The actions of the human being differ from the occurrences of outer nature in that they bear the impress of his inner life. In this way the soul represents what is man's own in
contradistinction to the outer world. He receives from the outer world the incitements; but he creates, in responding to these incitements, a world of his own. The corporality becomes the foundation of the soul being of man.