A contrary extreme, and of its kind a still more one-sided corrective of this too great stability, we have in those investigators who, by reason of the great progress which has been made in the realm of the theoretical knowledge of nature, allow themselves to be drawn on to the hope of still explaining all states and processes in the world--the spiritual and the ethic processes as well as the physical--from the pure mechanism of atoms; and who see in that which thus far has been mechanically explained, the only and the infallible way of explaining all that is still obscure. They call this view the _mechanical view of the world_; and, as "monism," put it in opposition to the "vitalistic, teleological, and dualistic view of the world." In order to obtain a correct view of this standpoint, we quote from Haeckel's "Natural History of Creation", Vol. I, page 23, the following passage: "By the theory of descent we are for the first time enabled to conceive of the unity of nature in such a manner that a mechanico-causal explanation of even the most intricate organic phenomena, for example, the origin and structure of the organs of sense, is no more difficult (in a general way) than is the mechanical explanation of any physical process; as, for example, earthquakes, the courses of the wind, or the currents of the ocean. We thus arrive at the extremely important conviction that _all natural bodies_ which are known to us are _equally {151} animated_, that the distinction which has been made between animate and inanimate bodies does _not_ exist. When a stone is thrown into the air, and falls to earth according to definite laws, or when in a solution of salt a crystal is formed, the phenomenon is neither more nor less a mechanical manifestation of life than the growth and flowering of plants, than the propagation of animals or the activity of their senses, than the perception or the formation of thought in man." Here crystallization, organic life, sensation, and formation of thought, are expressly put in one line of mechanism with the falling of a stone. In the following section we will have occasion to discuss this view as a _view of the world_; but we believe that the presentation of this idea, and the exclusive vindication of it as a complete view of the world, needs just here, where we still stand on the ground of the philosophy of natural perception, some critical sifting.