ALTHOUGH I am not yet entirely satisfied with it, I have decided to offer today, to the attention of thinking men, a work begun more than half a century ago. The method of scientific experiment, which is the only method of value in the search for truth, lays requirements upon us that we cannot and ought not to avoid. The grave problem considered in this treatise is the most complex of all problems and concerns the general construction of the universe as well as of the human being – that microcosm of the great whole. In the days of our youth we begin these endless researches because we are full of confidence and see a long life stretching out before us.