Evolution

by F. B. Jevons

If the theory of evolution comprehends all things, mind and morals as well as matter and motion; if the law of continuity connects all things together, immaterial as well as material, in a process which moves without break or interruption; it is because all things agree in the fact that they are presented (whether in sense or in idea) to the mind, and because they are presented in the continuity of consciousness.

But the object of the scientific mind is not to observe and record all the phenomena presented to it in the continuity of consciousness. On the contrary, it neglects and rejects many; but always with a purpose, viz. that of ascertaining and describing, as precisely as possible, the conditions under which a given co-existence or sequence occurs (and therefore may be expected to recur) and without which it fails to occur. In other words, science assumes that everything has a cause, and that in accordance with the uniformity of nature what has happened once will happen again in the same circumstances; that a cause will, in the absence of counteracting causes, produce its effect. Without these assumptions science cannot treat of any subject: no department of knowledge can be dealt with scientifically if these assumptions are not admitted with regard to that department. On the other hand, if by the aid of these assumptions we are enabled to reduce any set of phenomena to law and order, our success is of itself sufficient ground for regarding the assumptions as warrantable and justifiable. For science, at any rate, the only question is whether as a matter of fact they do enable us to determine under what conditions given co-existences or sequences will ensue, or what conditions such a co-existence or sequence necessarily implies.

With regard to human activity, mental and physical, it is plain matter of fact that such uniformities of sequence and co-existence not only can be but are demonstrated to prevail; and the extension of the scientific principle of cause and effect to the domain of human will and action is scientifically justified. The comparative sciences which deal with man and his works and words—archæology, anthropology, philology—are perpetually engaged in demonstrating, with fresh proofs every day, the uniformity of human nature: in similar circumstances men have always behaved in similar ways. To satisfy the same needs, they have manufactured similar instruments at similar stages of development: flint arrow-heads from Mexico or Japan resemble those taken from British barrows; the pottery of early Greece is hard to distinguish from that of Peru; the purpose of many stone implements of unknown antiquity has been discovered by a comparison of the use to which similar tools are put by savages still existing. That man's words, as well as his works, exhibit law, order, and uniformity in their growth, as well as in their phonetic decay, is shown by the science of comparative philology. That in the face of the same problems similar analogies have been used to produce similar solutions, is revealed by comparative mythology: the imagination, which might have seemed most free to throw off the trammels of law and of monotonous uniformity, falls in similar circumstances into very similar grooves.

If the will of man is not revealed in the things which he makes, in the words which he speaks, and the thoughts which he thinks, it is difficult to know where to look for its manifestation. If, on the other hand, it is manifested in these ways, then, whether it be free or not, it is clearly uniform in its action; and the extension to it of the law of causation seems fully justified by the results.

The recognition of the universality of the law of causation must not, however, be supposed to carry with it any implication that there are no differences between, say, the organic and inorganic, or that the laws of the one are identical with or deducible from those of the other; the association of ideas may be a scientific and established fact, and yet not obey the same laws as the adhesiveness of material substances. What unites all things into a continuous, coherent, and systematic cosmos, into a scientific whole, is first the fact that, whether phenomena in sense or phenomena in idea, they are all objects of thought; and next the fact that they all exhibit the universality of causation and the uniformity of nature.

Whether this uniformity which binds man and nature into one consistent whole is a uniformity of will or a uniformity of necessity, is quite another question. It is a metaphysical and not a scientific inquiry; and the metaphysical answer, whatever it may be, is one for which science does not and need not pause. So long as nature is granted to be uniform, it matters not to science whether the uniformity is of necessity or is freely willed. In either case the sequences or co-existences described by science will continue, under the circumstances described, to happen as described.

It is, however, commonly assumed that actions which are uniform are, by their very uniformity, proved to be necessitated; and that unless what happens was bound to happen, there can be no uniformity and no science. Hence on the one hand the recognition of the freedom of the will has been denounced as fatal to all scientific conceptions of human nature; while on the other hand the uniformity of human nature and action has been denied as being inconsistent with the freedom of the will. The one side has pointed to one set of facts, which prove irresistibly that men do will the same thing under the same circumstances. The other side has pointed to the equally undeniable fact of our consciousness of freedom.

The essential feature in our consciousness of freedom is our conviction that in the present we can do or abstain from doing a contemplated action, and in the past, though we did the thing, we might have abstained from it or have done something else. Now, whether this possibility that what took place might not have taken place is a real one or only a delusion, matters not to science. If real and true, it is indeed fatal to one particular metaphysical theory, viz. that every event which ever occurred was bound to occur and could not have happened otherwise; but it leaves every truth of science, every one of those concise descriptions of what takes place under given circumstances, absolutely intact. The freedom of the will is anathematised in the name but not in the interests of science.

That becomes clear when we reflect that the laws of science are, and do not pretend to be more than, hypothetical statements. The gravitation formula does not state that bodies do as a matter of fact actually fall at the rate of sixteen feet in the first second, and so on. The statement, if made, would be untrue: a feather floats much more slowly to the ground. Still less does the formula affirm that all bodies move towards each other—and for a very good reason: many bodies are at rest. The formula makes no definite statement as to what actually does occur: it merely states what would or will happen under certain circumstances; and it is doubly or trebly hypothetical. First, it asserts conditionally that if, and only if, bodies are free to move, they will tend to move towards each other at the rate of sixteen feet in the first second, and so on. Next, even if this condition be fulfilled in a particular case, and a given body is free to move, say, towards the earth, the law of gravitation does not assert that the body will absolutely, or unconditionally, or of necessity fall sixteen feet in the first second: it only affirms that the body tends to move at that rate, and the word "tends" conveys in its meaning a second hypothesis. What is meant by saying that a body tends to fall, or tends to move in a straight line, is simply that the body will fall or move in the direction or at the rate mentioned, provided that nothing happens to prevent it. The law of gravitation then, like every other law of science, from the very terms in which it is stated, contains two hypotheses: if bodies are free to move, then they tend to move at a certain rate. Further, like every other law of science, it is based on a third hypothesis, which, as it is assumed by all scientific laws, is not expressly referred to by any. That third hypothesis is that nature is uniform: if a body is free to move it will, in the future as in the past, tend to move at a certain rate, provided that nature is uniform.

Now, throughout all this, it is obvious that science knows nothing about "necessity." Indeed, it is obvious that science, by the trebly hypothetical form of all its laws, has taken particular pains to avoid prejudging the question whether what happens was bound to happen. As we have already said, science takes care to frame its statements in such a way that they are quite independent of metaphysical theory, and will remain as true within their limits if the theory of necessity prove erroneous as they will if it turns out to be correct.