This parallelism is no mere play of the intellect. If it is followed out it leads to significant ideas if not to actual knowledge. What penetrates from the outer world into the inner being of the organism is vibration, movement, force. Is the matter which is absorbed as nourishment ultimately anything different? Here we come up against the ultimate problems of physics, the various hypotheses regarding the nature of force and matter, the theories that in addition to matter there is an ether, or that the ether is a different, more subtle, form of matter, or that neither matter nor ether exist, but atoms out of which everything is built up, which themselves consist of electrons which are centres of force, motions without material consistency. All these theories, of which the last cannot be grasped by the human understanding, we can leave severely alone. This is not the place to investigate them. But the attitude of the living organism towards the outer world from which it absorbs nourishment and impressions, converting them into power to drive the life machine and transmuting them into consciousness, lends peculiar support to the supposition that force and matter are not only inseparable but identical, that in them we must seek a principle, or perhaps regard them themselves as a principle, which must be of the same nature as consciousness, for otherwise it could not be transmuted into the latter.
The senses are the means by which the outer world penetrates as an image into the inner being. Before the senses are differentiated the living organism possesses a general sensitiveness; that is to say, that under the influence of the outer world its cell protoplasm undergoes a process of regrouping, resulting in chemical and dynamic changes. The chemical results of stimulus are anabolism and katabolism, a building up and breaking down of the cell content; the dynamic results are movements which in the lowest forms of life are purely mechanical, but in the higher forms adapt the organism to the external influence in so far as they place it either so as to be affected by the latter as long and as powerfully as possible, or else so as to evade it. The living organism can experience no stimulus and respond to it without absorbing and transmuting it, converting it into a chemical process or a movement. This inner process is a subjective realization of something objective, a penetration by the outer world, therefore an elementary consciousness. In proportion as the general sensitiveness becomes differentiated into specific ones, as the image of the outer world filters through the different coloured glass panes of the various senses into the inner being of the organism, this image becomes multicoloured and varied.