VIII.

REVIEWS.

The Philosophical Basis of Evolution.-By JAMES CROLL, LL. D., F. R. S. London: Edward Stanford, 1890, pp. 198.

The late Dr. James Croll was in many respects a remarkable man, and the present little book, his last effort, is most characteristic of him. An earnest geological worker, he was also no mean mathematician and astronomer, and he was strongly tinctured with that love of metaphysics which is characteristic of so many hard-headed Scotsmen. The prevailing doctrines of evolution naturally attracted his attention, and many years ago, in his book "The Philosophy of Theism," and later in magazine articles, he endeavored to direct attention, in connection with these doctrines, to the violations of the great principle of causality-"Everything that comes to pass must have a cause"- involved in many of the discussions of those enticing and all-engrossing theories. His protests on this ground, however, though they attracted the attention of many thinking men, were necessarily, to the multitude, but as "the voice of one crying in the wilderness." The present book may be regarded as a last effort to bring back the attention of thinkers to what he considered to be fundamental principles, and possibly at this moment, when the current crude ideas are being so rudely shaken, the Scottish geologist's appeal to common sense may have some weight.

With Croll, evolution is more narrowly defined than with many writers. The evolution in which he believes is the succession of events in time whereby "a gradual transition has taken place from the simple to the complex, from the homogeneous to the heterogeneous, from indefinite to the more definite," and this under the domain of causality. Viewed in this way, rational evolutions should consist of series of ascertained sequences, as for instance those which occur in the evolution of a plant from a seed or an animal from an egg. These are matters of observation, and what science and philosophy have to do with them is to ascertain their true, efficient causes. Here he finds that there is great diversity of

opinion, and that many evolutionists regard the process as purely mechanical and physical, or the result of matter, motion, and force alone. This he holds to be a mistake, and defines the object of his treatise to be to show that it is absolutely impossible that "the process of nature can ever be accounted for without going beyond what is to be found in matter, motion, and force." He illustrates this by a reference to the great importance now attached to molecular motion in all physical questions, and by calling attention to the fact that in such molecular motions the essential question is not as to the fact of such motions, but as to the causes determining their direction. Hence the reasoner, who in explaining any evolution or development is content to limit his view to the mere forces involved, must necessarily fall short of any philosophical comprehension of the causes of the changes taking place. If, for instance, the molecules of a substance pack themselves together and form a regular crystalline form, it will not do to refer the evolution of such a form merely to attractive force; we must also consider what determines the action of such force in a manner to produce crystals of different forms in different substances, and in the same substance under different external conditions. Thus in the simplest kinds of development very complex and far-reaching questions occur, and these become complicated in an extreme degree in the development of organic forms. This great principle of determinism he thinks has been too much overlooked; and thus, as the writer of this notice has frequently maintained, the existing theories of evolution have degenerated into partial and imperfect explanations, and in many cases to a species of reasoning in a circle in which the end to be attained becomes the efficient cause of a process for its own attainment, and in which the complicated directions and determinations of energy are altogether overlooked. Nor is the idea of determination a new one, for I remember how strongly it was insisted on, before the rise of Darwinian evolution, in Dr. Chalmers's lectures. on natural theology; and Croll quotes many other eminent names in its support.

A simple illustration of this fallacy is afforded by a consideration of the development of heat, light, and mechanical force from the explosion of gunpowder, and of the forces and determinations of force involved in this. The explosion we may say was caused by the application of a spark of incan

descent matter, but to remain content with this explanation would imply a most superficial view, and even here we should have to consider the causes which determined the application of the incandescent spark, be it match or electric current, at the time and in the way in which it occurred. The cause of the explosion was in fact the chemical combination of certain substances previously existing in a state of fine mechanical mixture. Chemistry readily explains to us how this occurs, and can calculate the exact amount of the resulting force, and the precise states of combination of the several elements after the explosion. But behind all this we have the production of the carbon by vegetable life and organization; that of the sulphur perhaps by volcanic sublimation or by the aqueous decomposition of sulphates; and that of the nitre by the formation of nitric acid in nitre heaps or nitrous soil. All these must precede the mechanical mixture of the substances in our pound of gunpowder. But after all this, we have not touched the most serious question of all: what determined the mixture of all these materials in the exact proportions and conditions of aggregation necessary to produce the properties of the gunpowder.. If, in short, we are ignorant of the mys teries of the powder-mill, neither the explanations, however clear, of the spark evolutionist, the chemical evolutionist, or the mechanical evolutionist can give us any real explanation of the manner in which potential energy was stored up in the villainous compound in order to give it explosive

power.

But the explosion of gunpowder is itself an efficient cause, subject to determination. Our pound of powder is placed in a cannon with a ball in front of it, and the gun is so pointed and elevated as to drive the ball against the wall of a fortress which it breaches. Here the effects produced are determined among other things by the form of the gun, by the skill of the gunner, by the plans of the besieging general, by the exigencies of a war depending on the most complex political considerations. Clearly, the chemical and mechanical composition of gunpowder will not go very far to explain these determining causes, though, if Croll's views as to determinism be correct, many of the highest authorities on evolution tacitly assume that they do. They certainly do so when they take for granted that the complex determinations of molecules necessary to produce the structures and functions of plants and animals

can be explained merely by the interactions of chemical and physical forces.

He applies these considerations to life and vital force, and shows that whether we regard vital force as distinct altogether from other energies or as merely a modification of some of these, we cannot account for life and organization without taking into account the determinations of motion involved.

Applying these principles to current theories of evolution, he gives some of them the credit of recognizing the principle of determination, though in an imperfect way. Natural selection, for example, if it means anything more than a figure of speech, or blind chance, must refer to determinations by which certain structures or modifications of structure are selected and perpetuated, and others destroyed. But natural selection gives no explanation of the actual determining causes. As applied to the succession of animals and plants, it can mean nothing more than the destruction of those least suited to the conditions of their existence. It can itself produce nothing, nor can it determine the direction in which the development is to proceed. In the development of an eye, for example, it gives no explanation of what first determined the production of an organ intended to place the animal in relation to the undulations of light. It gives no good reason why these organs, when produced, are continued. It is not an efficient cause of any improvements of or additions to the organ. It can only have the effect of eliminating those animals which have, relatively to their needs, the least efficient eyes; and even in this it cannot explain what determines the path in which the developments shall proceed, or how this may be balanced or counteracted by other determinations, as for instance by swifter limbs or better teeth and claws possessed by animals less perfect in sight.

To return to our previous figure: The balls fired at the wall may in the first instance fall short of it, or pass over it, but the gunner raises or lowers the piece till he gets the exact range. Even if we take the skill of the gunner here to represent natural selection, this is only one factor in the great chain of determinations necessary to secure the result that the gun shall play upon the wall and breach it.

Our author, of course, feels that determinism means design and necessitates theism. He postulates as the necessary ultimate determining cause, an "Eternal God," without whom we

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can never have a rational and complete system of nature, whatever value may be attached to secondary causes, which must result from his determination.

Some details of this question he notices very ingeniously. Natural selection, he shows, cannot dispense with design, otherwise it becomes mere chance, which can effect nothing, or is reduced to a figure of speech. That an effect necessarily proceeds from its cause is no proof that the cause was not designed to produce it. The infallible accuracy of a rifle bullet is no evidence that the rifle was not designed to produce accurate firing. Natural selection cannot produce organisms, it can only modify those already produced. In so far as it has any efficiency, this can be only as a police force restraining and suppressing offenders. The apparent waste and destruction of germs and of living beings in nature, is no evidence against theism. It is on this, indeed, that we depend for the sustenance of a varied animal life, and for the maintenance and extension of all organic life in times of great geological vicissitudes. If a field could produce no more seed than what would barely suffice for next year's sowing, what would have become of agriculture? Civilized man himself could not in that case have existed. Even savages and wild animals would be constantly diminishing their food supply, and probably the earth would be in great part a desert. Various degrees of complexity and perfection are no evidence against design, for only in this way could the vast variety of kinds of life, and their suitableness for all situations, be produced. Rudimentary organs are no evidence against design. In many cases we have no proof that they are not useful, and any theory of evolution would necessitate their existence as the preparation for farther development or the means for enabling useful purposes to be served in certain coming contingencies. It would be no evidence against design to find in a machine certain parts at present not used, but intended to come into action in certain foreseen emergencies. Nor is the modification of similar structures to serve different ends an evidence against design. We do not ourselves always secure a new end by a new or different process, and we regard any invention, applicable by modification to many different ends, as on that account all the more remarkable as an evidence of intelligent plan.

Finally, Croll ventures to apply, not without success, his principle of determinism to the vexed questions of human