He first treats of _Naturalism_, that solution of the problem that makes
the sense experience of surrounding nature the basis of life,
subordinating even the life of the soul to the level of the natural,
material world.

Nature in the early ages had been superficially explained, often in the
light of religious doctrine. Man gave to nature a variety of
explanations and of colouring, depending largely upon his ideas of the
place of nature in relation to himself and to the invisible world. But
such anthropomorphic explanations could not long survive the progress of
the sciences, for a scientific comprehension of nature could only be
attained by getting rid of all human colouring, and by investigating
nature entirely by itself, out of all relation to the human soul. Man
then investigated nature more and more as an object apart from himself.

The first result of these investigations was to impress upon him the
reality of nature as something independent, and to increase on a very
large scale his knowledge of, and control over nature. When man began to
formulate and understand nature, he began, too, to invent machines to
profit from the knowledge he gained. Hence followed a marvellously
fruitful period of human activity, an activity which at first
strengthened man in his own soul, and gave him increased consciousness
of independence and power. While he was compelled to admit the greatness
of the natural world, he became more and more convinced that he himself
was far greater, for could he not put the laws of nature to his own use
and profit? Hence the gain to man at this stage of the development of
the sciences was very great, for he had come to appreciate more than
before the superiority of the human soul over the material world. Hence
resulted a more robust type of life, "a life energetic, masculine,