It was universally held by those, philosophic and simple, who also held throughout so many centuries the belief in spontaneous generation, that there is an overwhelming contrast between living and lifeless matter, and it was their belief in this overwhelming contrast that led them to give to the doctrine of spontaneous generation, as they held it, a form which cannot possibly be defended. The great character of life was conceived to be self-movement, this self-movement being displayed in the matter which composed the living organisms. But it was universally held that matter, as it was seen otherwise than in living organisms, was obviously and notoriously inert, gross, brute, and dead. [Sidenote: The Influence of Plato] The great influence of Plato taught men to despise matter in this fashion, and there was the everyday experience that a stone lies where it is placed until something from outside moves it, being, therefore, inert, whilst a living creature such as a bird moves freely at its own will. The more strongly men held the natural matter of which the earth is composed to be inert, the more necessary was it to suppose that when life was displayed in it the difference consisted in the taking possession of this dull clay by a vital force--a mystic and wonderful principle of quickening--which endowed even gross, inert matter with activity and power. From the time of Plato until the last few years of the nineteenth century thinkers vied with one another in insisting upon the impotence and grossness and inertness of matter, and each fresh insistence upon this doctrine rendered more necessary a corresponding doctrine of vital force or vitalism, which should explain the amazing transformation undergone by, let us say, the gross and inert matter composing food, when that food was converted by the “living principle” into the tissue of a living creature, and then displayed self-movement. [Sidenote: Philosophy of Dead Matter] [Sidenote: The Great Work of Pasteur]