Evolution

by F. B. Jevons

Now, to these questions, as to the Being and Becoming of the universe, science has nothing to say. Science does not even afford the materials for an answer to them, any more than to those other questions as to how or why things should happen in the way which science describes. Science describes things, but does not undertake to prove that things exist. Science is organised common sense, and common sense takes it for granted that things exist. Having made this assumption, science proceeds to investigate with scientific exactness the order in which events succeed one another and co-exist with one another, within the range of direct observation; and infers that, even when they are beyond the range of direct observation, they continue to occur in the same order of sequence and co-existence. But here again science refuses to have anything to do with any metaphysical questions as to how or why things should thus occur. All sorts of conjectures may be made, and have been made, to explain why B should follow A, or co-exist with it. But science is not pledged to any of them. The only thing she undertakes to show is the fact of the sequence or co-existence; and this she can do without assuming the truth of any of these conjectures. Indeed, the progress which science has made is largely due to the fact that she has steadily declined to have anything to do with such conjectures—having found out by experience that they simply distract her from her proper business of observing with the utmost exactness what actually does take place. It may be that A in some mysterious and wholly inexplicable way "produces" B, that is to say in technical phraseology, is "the efficient cause" or "mechanical cause" of B. It may be that the sequence of B upon A is a volition of the Being which is manifested in all thinking things, in all objects of all thought. Science cannot prove, and will not even discuss, either suggestion: she confines herself to the assertion that, as a matter of careful and exact observation, B does follow A. Whether we call A an efficient cause or not, matters not to science: call it so or refuse to call it so, the fact once established by science, that B follows A, remains. The theory of efficient or mechanical causes is doubtless of importance, but not to science. If it is proved to be false, not a single fact of science is shaken.

The mechanical theory may be true or may be false, but in either case it is a metaphysical theory. If science is descriptive—descriptive of the uniform succession and co-existence of facts—then science no more proves the mechanical theory to be true than it proves the volitional theory to be true. Both are theories as to why facts should succeed one another in the order described by science; and science does not undertake to prove the truth of such theories, nor does she wait for them to be proved or disproved.

Many men of science, however, are also philosophers, and hold, as they are fully entitled to hold, that the mechanical theory is the true interpretation of nature. Now, "mechanics is the science of motion; we can assign as its object: to describe completely and in the simplest manner the movements which occur in nature."[13] On the mechanical theory, therefore, "the object of all science is to reduce the phenomena of nature to forms of motion, and to describe these completely and in the simplest manner ... the only complete description is that afforded by a mathematical formula, in which the constants are supplied by observation. This permits us to calculate those features or phases of phenomena which are hidden from our observation in space or in time."[14] This, we need hardly add, is in agreement with Mr. Herbert Spencer's view of the theory of evolution as a description of the process of the redistribution of matter and motion.

It seems, then, that according to this particular metaphysical theory, which maintains the mechanical explanation of nature to be the true one, the object of all science is to describe (with mathematical accuracy, where possible) the movements of things in space. But science is universal; evolution extends to the whole cosmic process. Therefore, the only things with which science has to do, or which are factors in the cosmic process, are things moving in space.

As a metaphysical argument this theory seems to us unsatisfactory. It converts, simply and illegitimately, the proposition sanctioned by common sense, that material things are real, into the proposition opposed to common sense, that all real things are material. It assumes, apparently unconsciously and certainly without proof, that the only things capable of scientific description are movements in space, the only laws in the universe mechanical laws.

Historically, material things were the first to be studied and described with scientific exactness. It is only natural, therefore, that the methods and assumptions which have been employed with conspicuous success by the physical sciences should be extended, tentatively at least, elsewhere. It is equally natural that protests should be raised, and the extension proclaimed by philosophers to be illegitimate—"impoverishing faith without enriching knowledge."[15] "To regard the course of the world as the development of some blind force which works on according to universal laws, devoid of insight and freedom, devoid of interest in good and evil, are we to consider this unjustifiable generalisation of a concept, valid in its own sphere, as the higher truth?"[16]

It is not, however, likely that science will drop a generalisation, however "unjustifiable" in metaphysics, if it works in practice. The question is whether it does work; and that is plainly a question of fact, not a question of metaphysics. We want to know therefore, first, whether things moving in space are the only things with which we are acquainted in common experience; and, next, whether all the changes which take place within the range of scientific observation are or can be explained by the laws of mechanics.

It is clear that, if the mechanical theory of science and of evolution is to be successfully maintained, both these questions must be answered in the affirmative. It is equally clear that, if we confine ourselves to the actual facts, both questions must be answered in the negative.

Thoughts, ideas, conceptions, sensations, feelings, emotions are things of which we have experience at every moment of our waking lives; and none of them are things which occupy space or move in space. A thought is not a thing which can be measured by a foot-rule, as things in space can be; the greatness of an idea is not one which measures so many yards by so many; a conception has no cubic contents; a toothache cannot be put in a pair of scales, nor can any process of chemical analysis be applied to hope or fear. We find ourselves, therefore, in this dilemma: if the mechanical theory is true, and science can deal only with things moving in space, then psychology and sociology are not sciences, and their subject-matter never can be made amenable to scientific treatment. On the other hand, if psychology is a science, then science deals with things which do not move in space.

We submit that psychology is a science, that our sensations, emotions, ideas, etc., can be observed, and can be described scientifically, that is to say, that their uniform sequences and co-existences can be stated with accuracy and formulated as laws. We submit further that our definition of science should be based on facts, and not framed to suit a metaphysical theory. A satisfactory definition of science must include all the sciences. The definition put forward in the interests of the mechanical theory excludes arbitrarily the mental and moral sciences, and implies that their subject-matter is beyond the power of science to deal with. The exclusion and the implication are consequent upon the suggested limitation of science to things moving in space, and are of the essence of the mechanical theory. Both the exclusion and the implication are unnecessary if we adhere to the older conception of science, as it occurs in Mill, which claims for science all phenomena of which the sequences and co-existences can be observed, described, and formulated as laws.