Wide as is this range, it is to be penetrated everywhere by the light of science, which is to guide the explorer in every direction to the desired solution. In this bold venture science claims to be positive, and to rest solely on demonstration.

The canon proclaimed as regulative, at least theoretically regulative, is: "In positive science nothing can be assumed."

How this canon is observed, and this claim is maintained by the modern theory of forces, will the better appear as we advance.

Observation and experiment have ascertained the convertibility of light, heat, electricity, magnetism, chemical affinity, etc. Hence has been deduced the principle of correlation of forces. And, as these forces are only transmuted, not destroyed, by this correlation, another principle has been deduced-the conservation of energy, or the indestructibility of force. Indestructibility relates to the quantity of force; convertibility relates to the quality of force.

For ourselves, we are ready to admit that there is a theory of forces which is both ultimate and unquestionable-that there is an equivalence and a correlation of forces which the world has been only too slow to recognize-that the conservation of force is a principle which science may well maintain—that the persistence of force, if properly explained, must

commend itself to universal acceptance, and that the doctrine of evolution, if relieved of absurdities, is valid. But this conclusion turns, mainly, upon the conception of forces and the scope of their correlation, and involves the essential question, whether life and mind are forces-a question which runs through

the entire discussion.

It will be remembered that Prof. Grove, among the first to introduce the terms correlation and conservation, speaks of forces as related to matter, and the conservation and correlation of forces as confined within the range of material nature. (See his Lecture, 1842, quoted approvingly by himself in later lectures.)

M. Faraday, who regarded the conservation and correlation of forces as the highest law hitherto discovered in physics, also employed the term force as related to matter, and applied correlation and conservation of forces within the range of material

nature.

We are ready not only to accept but to maintain this view of the correlation and conservation of forces as presented by Grove and Faraday, and other earlier advocates of the theory of forces.

But within the last decade the notion of force has been enlarged, and the scope of correlation has been extended far beyond the realm of matter.

Although the general principle is correct, viz. : Conservation and Correlation; yet, the theory of forces, amplified as it is, and diverse and contradictory as we shall see, shows how immature are many of the notions on this subject, and how easy it is in the enthusiasm of scientific speculation to fall into error in applying the general principle.

Let us examine this theory in the light of its own definitions. While these definitions should be clear they should not be contradictory. They should mark, at once, the precise and permanent limit to the application of the theory. It is preposterous to talk of the correlation of forces without understanding what force is. It is still more preposterous to talk of forces as affections of matter without understanding what matter is—whether force is matter, and whether mind, as some affirm, is the most highly concentrated force.

In the slightest hazard we cannot submit to guidance which does not know its way. A fortiori, we cannot submit ourselves to unwitting guidance, when the very nature of matter and mind is involved, when our own origin and destiny, the very origin and destiny of thought and being, are involved.

According to Mr. Grove, force, though so subtle as to elude the senses, is real and casual-the producer or cause of motion; (passim).

While this definition may apply in dynamics, it is evidently inadequate in statics, as Mr. Grove himself admits," in the case of equilibrium of two arms of a balance;" and so, we may add, in every case of statics where balanced forces of indefinite degree may produce static repose in any degree.

Dr. Mayer, of Heilbronn, in his paper on "The Forces of Inorganic Nature," p. 251, says: "The term force conveys the idea of something unknown and hypothetical.”

On the other hand, he tells us, p. 252, that "forces are indestructible, convertible, imponderable objects."

Dr. Bray, in his Anthropology, etc., p. 164, declares with scientific enthusiasm: "Force is everything." And, doubtless to be more explicit, he says on p. 220,"The scientific idea of force is the idea of as pure and mysterious a unity as the one of Parmenides. It is a noumenal integer phenomenally differentiated into the glittering universe of things.'

It is a relief to turn from this dazzling definition to the milder utterance of Faraday: "What I mean by the word force is, the cause of a physical action."

As this restricts the effect to the limit of physics, so it would seem to restrict the cause-though the statement is indefinite.

Dr. Bastian, in his labored work on "Force and

Matter," I. p. 4, explains force to be a mode of motion, differing again from all that precede him in regarding force as neither effect nor cause, but as the mode of an effect.

Herbert Spencer, First Princ., p. 266, says: "Force, as we know it, can be regarded only as a certain conditioned effect of the unconditioned cause, as the relative reality, indicating to us an absolute reality by which it is immediately produced." And Prof. Barker, as if deliberately to increase the confusion, says in a lecture devoted to the elucidation of this subject: "By actual energy as contradistinguished from potential energy is meant motion. It is in this latter sense that we shall use the word force in this lecture." (Correlation of the Vital and Physical Forces, p. 7.)

This is a sample of the definitions which could be greatly extended. And, yet, under the threat of censure from this school of "more advanced thinkers," as Prof. Barker styles them, we are required to adopt their theory of forces.

From these confused and contradictory definitions of force, we turn to the view of matter as presented by this modern theory. Does it distinguish or identify matter and force?

As we have already seen, Mr. Grove says, "Forces are the affections of matter," thus distin