THE NATURE OF MAN
1. The Corporeal Being of Man
We learn to know the body of man through bodily senses. And the way of observing it can differ in no way from that by which we learn to know other objects perceived by the senses. As we observe minerals, plants, animals, so can we observe man also. He is related to these three forms of existence. Like the minerals he builds his body out of the materials of Nature; like the plants he grows and propagates his species; like the animals, he perceives the objects around him and builds up his inner experiences on the basis of the impressions they make on him. We may therefore ascribe to man a mineral, a plant, and an animal existence.
The difference in structure of minerals, plants and animals corresponds to the three forms of their existence. And it is this structure — the shape — which we perceive through the senses, and which alone we can call body. Now the human body is different from that of the animal. This difference everybody must recognise, whatever he may think in other respects regarding the relationship of man to animals. Even the most thorough-going materialist, who denies all soul, cannot but admit the truth of the following sentence which Carus utters in his Org anon der Natur und des Geistes: “The finer, inner construction of the nervous system, and especially of the brain, still remains an unsolved problem for the physiologist and the anatomist; but that this concentration of the structures increases more and more in the animal, and in man reaches a stage unequalled in any other being, is a fully established fact; a fact which is of the deepest significance in regard to the mental evolution of man, of which, indeed, we may go so far as to say it is really in itself a sufficient explanation. Where, therefore, the structure of the brain has not developed properly, where smallness and poverty are revealed as in the case of microcephali and idiots, it goes without saying that we can as little expect the appearance of original ideas and of knowledge, as one can expect propagation of the species from persons with completely stunted organs of generation. On the other hand, a strong and beautifully developed build of the whole man, and especially of the brain, will certainly not in itself take the place of genius, but it will at any rate supply the first and indispensable condition for higher knowledge.”
Just as we ascribe to the human body the three forms of existence, mineral, plant, animal, so we must ascribe to it a fourth, the distinctively human form. Through his mineral existence man is related to everything visible; through his plant-like existence to all beings that grow and propagate their species; through his animal existence to all those that perceive their surroundings, and by means of external impressions have inner experiences; through his human form of existence he constitutes, even in regard to his body alone, a kingdom by himself.