This material is and must be the product of art. If the forces of inorganic nature spontaneously produced sugar, starch, etc., these substances must have the same quality as our rocks, minerals, etc., of being products of combustion, which in such a supposed case, perhaps, would be made burnable if transformed into water and carbonic acid. We would obtain a creation turned upside down and analogous to a world where the bodies we now use as weights would remain unsupported at certain distances from our earth. If we were to use such a body as a weight in a clock, we would have to wind it down instead of up. Because organic compounds are products of art, living beings find themselves obliged to direct the physical forces to destroy these compounds or restore them to their inorganic state more speedily than these forces would have done if left unaided. The processes of decay, performed by micro-organisms, are as necessary in the economy of life as the reverse processes. Otherwise the earth would soon be so covered by corpses that life must cease simply for lack of inorganic raw material. It is true that we might imagine living beings as adapting their organization to this condition and for some time directly utilizing the accumulated stores of organic matter; but such periodical interruptions and changes would disturb the continuity of life’s evolution. To avoid this, there is no way open to restore equilibrium except the one in which it is now done. No effect, whatever its nature, can exist without cause; and further, every effect must have a sufficient cause. If, therefore, we have established that natural forces can no more produce organisms than steam engines, we have also proved that these things would never have come into existence if the organic forces had been left to themselves. Neither organisms nor engines would exist, because they have no cause in the material world. The products of art are due not only to other causes, but the relationship between cause and effect is also different with them from what it is with the products of nature. Every product of nature has its cause in a previous condition of matter. The cause goes before and the effect comes after in time. The connection between cause and effect is so intimate and complete with regard to natural products, that we may trace the series of occurrences backward and forward in time without other limitations than those imposed by a deficient knowledge of the qualities of matter. Such a connection between cause and effect has been termed mechanical causality, which reigns without exception in the material world.