We are now in a position to see the fallacy of Moleschott's often-quoted aphorism, "No thought without phosphorus!" When this saying was a new one, there were worthy people who felt that somehow it was all over with man's immortal soul. With phosphorus you light your candle, and with phosphorus you discover Neptune and write the Fifth Symphony; how charmingly simple and convincing! And yet was anything save a bit of rhetoric really gained by singling out phosphorus among the chemical constituents of brain tissue rather than nitrogen or carbon? Suppose the dictum had been, "No thought without a brain." The obvious answer would have been, "If you refer to the present life, most erudite professor, your remark is true, but hardly novel or startling; if you refer to any condition of things subsequent to death, pray where did you obtain your knowledge?" Nevertheless this point cannot be disposed of simply by exhibiting the flaw in Moleschott's rhetoric. His remark rests upon the assumption that conscious mental phenomena are products of the organic tissues with which they are associated. This is of course the central stronghold of materialism. A century ago the case was very boldly put when we were asked to believe that the brain secretes thought as the liver secretes bile. Nobody to-day would think of making such a comparison, but it is more cautiously stated that consciousness is a "function" of the brain, or at all events of the nervous system, even as bile-making is a function of the liver. Before we yield any modicum of assent to this statement we may observe that "function" is a word with a wide range of meaning, and we must insist upon some closer definition. Here materialism calls to its aid the discovery of the correlation and equivalence of forces, one of the most stupendous achievements of our century. We now know that heat and light and electricity and actinism are not forces generically distinct and isolated each from the others. All are specific modes of molecular motion, transformable one into another at any moment as naturally as a cloud condenses into raindrops. Any such molecular motion, moreover, may come from the arrested visible motion of a mass, and may in turn be liberated so as to resume the form of visible motion, as when an electric current is transformed into the onward movement of the trolley car. The change in our conception of Nature that has been wrought by this wonderful discovery is more profound than all changes that went before. The balance in the hands of the chemist had already proved that no matter is ever lost but only transformed, and that every material form at any moment visible owes its existence to the metamorphosis of some previous form. So now it was further shown that the myriad properties or qualities of matter are simply the expression of myriads of activities which are all in a final analysis motions; that no motion is ever lost but only transformed, and