Nevertheless, when subjected to criticism, this theory of things soon loses its sober and plausible appearance and is seen to be eminently rash and shallow. In the first place, there is no such correlation or equivalence as is alleged between physical forces and the phenomena of consciousness. The correlations between different modes of motion have been proved by actual quantitative measurement, and never could have been proved in any other way. We know, for example, that heat is a mode of motion; the heat that will raise the temperature of a pound of water by one degree of Fahrenheit is exactly equivalent to the motion of 772 pounds falling through a distance of one foot. In similar wise we know that light, electricity, and magnetism are modes of motion, transferable one into another; and, although precise measurements have not been accomplished, there is no reason for doubting that the changes in brain tissue, which accompany each thought and feeling, are also modes of motion, transferable into the other physical modes. But thought and feeling themselves, which can neither be weighed nor measured, do not admit of being resolved into modes of motion. They do not enter into the closed circuit of physical transformations, but stand forever outside of it, and concentric with that segment of the circuit which passes through the brain. It may be that thought and feeling could not continue to exist if that physical segment of the circuit were taken away. It may be that they could. To assume that they could not is surely the height of rash presumption. The correlation of forces exhibits Mind as in nowise a product of Matter, but as something in its growth and manifestations outside and parallel. It is incompatible with the theory that the relation of the human soul to the body is like that of music to the harp; but it is quite compatible with the time-honoured theory of the human soul as indwelling in the body and escaping from it at death.