With a clearer apprehension of the terms, we may now discuss the first proposition with more precision, and hope to reach a logical conclusion. We approach the discussion by remarking—
1. The constancy of the course of nature or the uniformity of causation is not a self-evident and necessary truth. In so far as it is a scientific truth it is purely an induction from experience, an experience which is necessarily limited, and therefore does not warrant a universal conclusion. There is no rational à priori ground for the assumption that the same or similar causes (even if we understand by physical causes all antecedent conditions) shall necessarily produce the same effects. In other words, there is no authority for the assertion that the course of nature or the procession of phenomena must be absolutely uniform. Science has succeeded in establishing a strong probability, but it is beyond her power to demonstrate an absolute certainty. This is generally conceded, alike by physicists and metaphysicians. J. S. Mill says, "The uniformity in the course of events ... must be received, not as a law of the universe, but of that portion of it which is within the range of our means of observation, with a reasonable degree of extension to adjacent cases."[452] "The uniformity of causation," says Murphy, "is not a truth of the reason, it is known by experience only; and the truth of a conclusion from experience can never be free from all possibility of limitation or exception."[453] And Professor Jevons asserts, "The conclusions of scientific inference appear to be always of a hypothetical and purely provisional nature. Given certain experience, the theory of probability yields us the true interpretation of that experience, and is the surest guide open to us. But the best calculated results which it can give us are never absolute probabilities: they are purely relative to the extent of our information. It seems to be impossible for us to judge how far our experience gives us adequate information of the universe as a whole, and of all the forces and phenomena which can have place therein."[454]
2. It is an immediate fact of consciousness that the will is a cause which is adequate to the production of a diversity of effects. Whatever may be true of the world of matter, it is certain that within the sphere of our conscious personality the relation of cause and effect is not a relation of invariable and necessary sequence. Further, it is certain that a self-determining agent exists. "Every event in the universe of matter is determined by the events which precede it, but physical reasonings make it certain that the chain of causes and effects can not have been of absolutely endless length through past time. There must have been a first link of the chain; there must have been a first act of causation; and this act must have been determined, not by any previous act of causation when as yet there was none, but by the free self-determining power of the agent. The first act of causation we call Creation; the freely self-determining agent we call God."[455]
3. Physical science itself does not teach that the course of nature is absolutely uniform; on the contrary, all the conclusions of science lead to the conviction "that the universe is ever changing, and that, notwithstanding secular recurrences which would primâ facie seem to replace matter in its original position, nothing in fact ever returns or can return to a state of existence identical with a previous state."[456] Every theory of the origin of things is compelled to assume that an innate tendency to variability is a fundamental fact of nature. This is made apparent by the reasoning in Spencer's chapters on "The Instability of the Homogeneous" and "The Multiplication of Effects."[457] The advocates of Natural Selection are very emphatic in the assertion of this "Law of Variation," as the cardinal fact upon which turns their doctrine of the origin of species, and the whole system on which organic life has been developed from the lowest to the highest forms.[458] "There is," says Comte, "an irregular variability of effect engendered by the great number of different agents determining at the same time the same phenomena [meteorological, social, and vital], from which it results in the most complicated phenomena that there are not two cases precisely alike." "The multiplicity [of the agents] renders the effects as irregularly variable as if every cause had not been subjected to any previous conditions."[459] Dr. Tyndall himself is in fact compelled to surrender the doctrine of uniformity in the succession of phenomena. He says "if the force be permanent, the phenomena are necessary whether they resemble or do not resemble any thing that has gone before."[460] But if the phenomena do not resemble any thing that has gone before, how can there be "uniformity" in the succession of phenomena?
4. The uniformity of the constitution of material nature, or the principle that the same substances must always have the same essential properties, is undoubtedly a self-evident and necessary truth, an à priori, rational intuition. It is simply a statement in concrete form of the principle or law of identity (A = A, or A is not equal to non-A). As we have already observed, a substance which ceases to have the same essential properties ceases to be the same substance; for substances are only known to us through their properties. But this "uniformity of co-existence" is distinct from "uniformity of succession," and we can not infer the latter from the former. Admitting that the same substance must always have the same properties, we can not affirm that the same substances will always be collocated in the same manner, or distributed in space with the same uniformity. In fact, "we can discover nothing regular in the distribution of matter through space; we can reduce it to no uniformity, to no law."[461] Matter is never replaced in its original position; "nothing repeats itself, because nothing can be placed in the same conditions; the past is irrevocable."[462]
Even should we say with Sir William Thomson that "motion constitutes the very essence of what is commonly called matter," still we know with infallible certainty that there must be a something that moves, and that this something which moves must have ultimately a definite mass (inertia) and a measurable velocity, and that the energy of motion to which the power of doing work is due is proportionate to the mass multiplied into the square of the velocity. Matter, then, is something more than motion.[463] We know further that there are different "modes of motion"—transitive, rotatory, vibratory, pulsatory, gyratory—and that these are undergoing perpetual transformation or conversion one into the other. And, finally, we know that the quantities of visible molar energy, and of invisible molecular energy (as heat, light, electricity, magnetism), are not uniform; on the contrary, the quantity of mechanical energy is being continually dissipated—that is, transformed into radiant heat, "which may be compared to the wasteheap of the universe,"[464] and uniformly diffused heat will not yield a single unit of work.
The principle of the conservation of energy is therefore subject to limitations which are supplied by the principle of the dissipation of energy. It simply asserts that, so far as our observation extends, the whole amount of potential and kinetic energy in the universe is invariable, but it can not determine whether the amount of vital force, or of psychic force, is invariable; and it is certainly incompetent to fix a limitation to the exercise of Creative Power. "It is nothing more than an intelligent and well-supported denial of the chimera of perpetual motion, and that a machine can no more create work than it can create matter."[465] In the words of Grove, we can not conceive of the production of any new force in the universe "without the interposition of Creative Power."[466]
Dr. Tyndall, in his solicitude to exclude all Divine interposition in the economy of nature, has stated the law of the conservation of energy in a form quite different from that of his scientific brethren. He says, "The principle of conservation is, no creation but infinite conversion;"[467] and he seems desirous to convey the impression that any interposition of God to answer prayer would be a creation of physical force, and as much a miracle as the rolling of the waters of the St. Lawrence up the Falls of Niagara. Dr. Tyndall does not here display his usual fairness and candor. Surely he would not assert that the qualitative and quantitative combination of the different natural agents—such as light, heat, electricity, elasticity of vapors, and aerial currents—which determine the fall of a shower of rain, would be a creation of energy; or that the disposition of the meteorological, physical, chemical, vital, and psychical conditions which result in the cure of the sick, would be as much a miracle as "the stoppage of an eclipse;" for these natural agents are more or less under the control of man. But suppose it were granted that all interposition of God in the economy of nature must be regarded as miraculous, would he deny the possibility of miracles even if they should involve a creation of energy? Because we can not by any of our mechanical arrangements create energy, does it therefore follow that God can not create energy? Dr. Tyndall will not say this. "If you ask who is to limit the outgoings of Almighty power, my answer is—not I."[468]
It will be seen presently that Dr. Tyndall admits that the interference of personal volition in the economy of nature is not forbidden by the law of the conservation of energy. The point we now insist upon is that he has not succeeded in showing that this principle is an absolute and universal law of nature. We have already seen that it is limited and conditioned by the law of the dissipation of energy, and that in reality "it is merely a kind of movable equilibrium between supply and destruction."[469] By no experimental evidence has it been shown that it holds true in the realm of vital dynamics and psycho-dynamics. There are able scientific men who question its absolute certainty even in the realm of physics. Professor Brooke says that "the amount of energy in the world is unchanged, the sum of the actual or kinetic and potential energies being a constant quantity has been by some writers overstrained. It may be taken as a postulate, and is probably true; but it is a proposition equally incapable of proof and of disproof."[470] To the same effect are the words of Sir John Herschel,[471] and still more recently of Professor Jevons.[472]
"Nature," says Dr. Cohn, of Breslau, "is an equation with very many unknown quantities. It is the work of natural science to determine the value of these quantities. Some believe it never will be possible to solve the equation, since in it factors occur which can not be determined." Until this is done, it is simply presumptuous for Dr. Tyndall to pretend to know all the antecedents which determine the complex phenomena of nature, and dogmatically to affirm that "no new agency is created," and no "interference of Divine agency" can be permitted. "Our knowledge of things is finite, while our ignorance is infinite; and we must consequently regard all known lines of causation as being liable to be cut through by unknown ones." For aught we know to the contrary one of the unknown factors in the equation may be "personal volition," may be the ceaseless energy of the Divine Will sustaining and carrying nature forward through successive stages toward a predestinated goal. The foremost physicists do not deny that there may possibly be forms of energy which are neither potential nor kinetic.[473] We venture to assert with Prof. Challis that will, or personal energy, is neither the one nor the other, but the source of both. Mind is the originator, and matter is the recipient of force.[474]