This view can be briefly stated as follows: Everywhere in the wide realm of observation we find three distinct 1 See Vogt, Physiologische Briefe (1845-1847); Moleschott, Der Kreislauf des Lebens (1852); Buchner, Kraft and Stoff (1855).
Several causes, beginning towards the end of the 18th century, gradually led up to the materialism of Moleschott, Vogt and Buchner, which flourished in the middle of the 19th century.
Moleschott (1822-1893) made a diligent use of the science of his day in his Kreislauf des Lebens (1852).
Of matter from the inorganic to the organic world, moleschott and back again, and he urged this metabolism against the hypothesis of vital force.
Aristotle had imputed to all living beings a soul, though to plants only in the sense of a vegetative, not a sensitive, activity, and in Moleschott's time many scientific men still accepted some sort of vital principle, not exactly soul, yet over and above bodily forces in organisms. Moleschott, like Lotze, not only resisted the whole hypothesis of a vital principle, but also, on the basis of Lavoisier's discovery that respiration is combustion, argued that the heat so produced is the only force developed in the organism, and that matter therefore rules man.
Buchner (q.v.) himself said that he owed to Moleschott the first impulse to composing his important Buchner.
Passing from Moleschott to Lyell's view of the evolution of the earth's crust and later to Darwin's theory of natural selection and environment, he reached the general inference that, not God but evolution of matter, is the cause of the order of the world; that life is a combination of matter which in favourable circumstances is spontaneously generated; that there is no vital principle, because all forces, non-vital and vital, are movements; that movement and evolution proceed from life to consciousness; that it is foolish for man to believe that the earth was made for him, in the face of the difficulties he encounters in inhabiting it; that there is no God, no final cause, no immortality, no freedom, no substance of the soul; and that mind, like light or heat, electricity or magnetism, or any other physical fact, is a movement of matter.