Feuerbach here confuses materialism, which is a philosophy of the universe dependent upon a certain comprehension of the relations between matter and spirit, with the special forms in which this philosophy appeared at a certain historical stage--namely in the eighteenth century. More than that he confuses it with the shallow and vulgarized form in which the materialism of the eighteenth century exists today, in the minds of naturalists and physicians, and was popularized during a period of fifty years in the writings of Buechner, Vogt and Moleschott. But as idealism has passed through a series of evolutionary developments, so also has materialism--with each epoch-making discovery in the department of natural science it has been obliged to change its form; since then, history also, being subjected to the materialistic method of treatment, shows itself as a new road of progress. The materialism of the preceding century was overwhelmingly mechanical, because at that time of all the natural sciences, mechanics, and indeed, only the mechanics of the celestial and terrestrial fixed bodies, the mechanics of gravity, in short, had reached any definite conclusions. Chemistry existed at first only in a childish, phlogistic form. Biology still lay in swaddling clothes; the organism of plants and animals was examined only in a very cursory manner, and was explained upon purely mechanical grounds; just as an animal was to Descartes nothing but a machine, so was man to the materialists of the eighteenth century. The exclusive application of the measure of mechanics to processes which are of chemical and organic nature and by which, it is true, the laws of mechanics are also manifested, but are pushed into the background by other higher laws, this application is the cause of the peculiar, but, considering the times, unavoidable, narrowmindedness of the French materialism.