Remembering the picture of man's spiritual-physical evolution which we have gained from earlier chapters, we are not astonished to find how different this early experience of the breathing process was from our own. Yet, together with the recognition of this difference there arises another question. Even if we admit that man of old was so organized that the experience of his own breathing process was an overwhelmingly spiritual one, it was, after all, the gaseous substance of the earth's atmosphere which he inhaled, and exhaled again in a transformed condition. What then was it that prevented men - apparently right up to the time of van Helmont - from gaining the slightest inkling of the materiality of this substance? To find an answer to this question, let us resort once more to our method of observing things genetically, combined with the principle of not considering parts without considering the whole to which they organically belong.