[10]. Carpenter’s Prin. of Comp. Phys., p. 617.
CHAPTER IV.
THE CAUSES OF EVOLUTION.
§ 58. Is this law ultimate or derivative? Must we rest satisfied with the conclusion that throughout all classes of concrete phenomena such is the mode of evolution? Or is it possible for us to ascertain why such is the mode of evolution? May we seek for some all-pervading principle which underlies this all-pervading process? Can we by a further step reduce our empirical generalization to a rational generalization?
Manifestly this community of result implies community of causation. It may be that of such causation no account can be given, further than that the Unknowable is manifested to us after this manner. Or, it may be, that the mode of manifestation is reducible to simpler ones, from which these many complex consequences follow. Analogy suggests the latter inference. At present, the conclusion that every kind of Evolution is from a state of indefinite incoherent homogeneity to a state of definite coherent heterogeneity, stands in the same position as did the once ultimate conclusion that every kind of organized body undergoes, when dead, a more or less rapid decay. And as, for the various kinds of decomposition through which animal and vegetal products pass, we have now discovered a rationale in the chemical affinities of their constituent elements; so, possibly, this universal transformation of the simple into the complex may be affiliated upon certain simple primordial principles.
Such cause or causes of Evolution, may be sought for without in the least assuming that the ultimate mystery can be fathomed. Fully conscious that an absolute solution is for ever beyond us, we may still look for a relative solution—may try to reduce the problem to its lowest terms. Just as it was possible to interpret Kepler’s laws as necessary consequences of the law of gravitation, and then to admit that gravitation transcends analysis; so it may be possible to interpret the law of Evolution as the necessary consequence of some deeper law, beyond which we may nevertheless be unable to go.
§ 59. The probability of common causation, and the possibility of formulating it, being granted, it will be well before going further, to consider what must be the general characteristics of such causation, and in what direction we ought to look for it. We can with certainty predict that be it simple or compound, the cause has a high degree of generality; seeing that it is common to such infinitely varied phenomena: in proportion to the universality of its application must be the abstractness of its character. Whatever be the agency and the conditions under which it acts, we need not expect to see in them an obvious explanation of this or that species of Evolution, because they equally underlie species of Evolution of quite a different order. Determining Evolution of every kind—astronomic, geologic, organic, ethnologic, social, economic, artistic, &c.—they must be concerned with something common to all these; and to see what these possess in common, will therefore be the best method of guiding ourselves towards the desired solution.
The only obvious respect in which all kinds of Evolution are alike, is, that they are modes of change. Every phenomenon to which we apply the term, presents us with a succession of states; and when such succession ceases, we no longer predicate Evolution. Equally in those past forms of it which are more or less hypothetical, and in those forms of it which we see going on around, this is the common characteristic. Note next, that the kind of change which constitutes Evolution, is broadly distinguished from change of an equally general kind, in this, that it is change of internal relations instead of change of external relations. All things in motion through space are the subjects of change; but while in this which we call mechanical motion, the relative position as measured from surrounding objects is continually altered, there is not implied any alteration in the positions of the parts of the moving body in respect to each other. Conversely, a body exhibiting what we call Evolution, while it either may or may not display new relations of position to the things around it, must display new relations of position among the parts of which it is made up. Thus we narrow the field of inquiry by recognizing the change in which Evolution consists, as a change in the arrangement of parts: of course using the word parts in its most extended sense, as signifying both ultimate units and masses of such units. Further, we have to remember that this change in the arrangement of parts which constitutes Evolution, is a certain order of such change. As we saw in the last chapter, there is a change in the arrangement of parts which is not Evolution but Dissolution—a destructive change as opposed to a constructive change—a change by which the definite is gradually rendered indefinite, the coherent slowly becomes incoherent, and the heterogeneous eventually lapses into comparative homogeneity. Thus then we reduce that which we have to investigate to its most abstract shape. Our task is to find the cause or causes of a certain order of change that takes place in the arrangement of parts.