to its modern scientific form. It is admitted that it is the province of scientific men to discuss scientific questions ; and that much in- jury to the cause of truth has followed the attempts of men not devoted to such pursuits, undertaking to adjudicate in such cases. Physicists are wont to take high ground on this subject, and to warn off as intruders all metaphysicians and theologians, all who are devoted to the study of the supersensuous and the supernatural. They are not allowed to be heard on questions of science. The rule must work both ways. If metaphysicians and theologians must be silent on matters of science, then scientific men devoted to the study of the sensuous, are not entitled to be dictatorial in what regards the supersensuous. A man may be so habituated to deal with quantity and number, as to become incapable of appreciating beauty or moral truth. In like manner a man may be so devoted to the examination of what his senses reveal, as to come to believe that the sensible alone is true and real. The senses have their rights, and so have reason and conscience ; and the votaries of sense are not entitled to claim the whole domain of knowledge as exclusively their own.
While, therefore, it is conceded that it belongs specially to scien- tific men to deal with scientific subjects, yet other classes have some rights which are not to be denied. They have the right to judge for themselves on tlie validity of the arguments of scientific men ; and they have the right to appeal from one scientific man to another, and from the few to the many. So far as the correlation of physical and vital forces is concerned, it is not only a new doc- trine, but as yet is adopted only by " advanced thinkers," as they are called, and call themselves. Dr. H. B. Jones, F. R. S., one of the more modest advocates of the doctrine,^ says, "We are only just entering upon the inquiry how far our ideas of conservation and correlation of energy can be extended to the biological sci- ences." And certain it is that the leading men of science, both in Europe and America, are firm believers in vital and mental forces, as distinct in kind, from all physical forces operative in the inor- ganic world.
The Arguments for sucli Correlation are Invalid.
The Argument from Analogy.
It has already been stated on the authority of the advocates of
the theory, that their first and most important argument in ita
support is from analogy. The physical forces are all correlated ;
1 Croonian Lectures, p. 66.
286 PART I.— THEOLOGY. [Ch. HI. — Anti-Theism.
one is convertible into either of the others ; all may be resolved into motion. This creates, as it is said, a strong presumption, that all force, whatever its phenomena, is essentially the same thing. If one kind of motion is heat, another electricity, another light, it is fair to infer that vitality is only another kind 'of motion, and thought and feeling another. As there is no reason for assuming a specific force for light, and another for heat, therefore it is un- necessary, and unphilosophical, to assume a specific kind of force to account for vital or mental phenomena. Prof. Barker of Yale College, says,i " To-day, as truly as seventy-five years ago when Humboldt wrote, the mysterious and awful phenomena of life, are commonly attributed to some controlling agent residing ip the organism — to some independent presiding deity, holding it in absolute subjection." This presiding agent is called " vital fluid," " materia vitce diffusa,'" " vital force." " All these names," he adds, " assume the existence of a material or immaterial something, more or less separable from the material body, and more or less identical with the mind or soul, which is the cause of the phenom- ena of living beings. But as science moved irresistibly onward, and it became evident that the forces of inorganic nature were neither deities nor imponderable fluids, separable from matter, but were simple affections of it, analogy demanded a like concession in behalf of vital force. From the notion that the effects of heat were due to an imponderable fluid called caloric, discovery passed to the conviction that heat was but a motion of material particles, and hence inseparable from matter ; to a like assumption concerning vitality [namely, that it also is but a motion of material particles], it was now but a step. The more advanced thinkers in science of to-day, therefore, look upon the life of the living form as insepara- ble from its substance, and believe that the former is purely phe- nomenal, and only a manifestation of the latter. Denying the existence of a special vital force as such, they retain the term only to express the sum of the phenomena of living beings."
The argument from analogy is presented, as we have seen, in another form, by Huxley and others. The properties of water are very different from those of the hydrogen and oxygen of which it is composed. Yet no one supposes that those properties are due to anythino- else than the material composition of the water itself. So also the phenomena of living matter, and of the human brain, are very different from those of the elements which enter into their constitution ; but this affords no presumption that there is any
1 Correlation of Vital and Physical Forces, p. 5.