As to the theory itself, it suggests a curious reflection, that nature might have caused sound to travel, not at the rate of 340 metres a second, and that its velocity, which depends on the density and the elasticity of the air, might have been very much less. Now see what would be the result if this were the case. Men would not be able to speak to one another when walking together. In that case we could not speak whilst walking, and three-fourths of mankind would not be able to hear one another. None of your acts are absolutely free and independent.
Man is the obedient, though unconscious, creature of the organic forces of the Earth.
The human organism derived from the Earth. Could one know exactly the faculties of his soul and the circumstances which were to surround his life, one could write beforehand that man's life in all its details. The human organism is the product of the planet. It is not by a Divine fantasy, by a miracle, or by a direct creation that terrestrial man is constituted such as he is. The whole of terrestrial life, from the mollusc to man, is the development of one single and sole genealogical tree.