5. The human being needs spiritual self-knowledge for inner peace. He finds himself in his thinking, feeling and willing. He sees how thinking, feeling and willing are dependent upon the natural human being. Where health and illness are concerned, they must follow the physical body in its strength and debilitation. Sleep extinguishes them. Life's experiences show how dependent spiritual experience is on the physical body. One may therefore come to the conclusion that self-knowledge is lost amidst these everyday experiences. Then the essential question arises: whether self-knowledge and therewith certainty about the true self, beyond ordinary experience, is even possible. Anthroposophy wishes to answer this question based upon sound spiritual experience. It is not based on mere opinion or belief, but on experience of the spirit, which is as certain as the experience of the body.