Читать книгу Parallel Paths: A Study in Biology, Ethics, and Art - T. W. Rolleston - Страница 5

Table of Contents

THE ARGUMENT FROM DESIGN

“The wisdom of the divine rule is apparent not in the perfection but in the improvement of the world.”—Lord Acton.

PALEY’S Natural Theology though not by any means an epoch-making may perhaps be called an epoch-marking book. It was the crown of the endeavour of eighteenth-century religious philosophy to found a theology on the evidences of external nature. According to such exact knowledge of Nature’s operations as was then generally available, Paley’s attempt might well be thought to have succeeded. He opens his argument with a striking and effective illustration. He imagines a wayfarer crossing a heath who strikes his foot against a stone, and who asks himself how it came into being. Paley thinks he might be content with vaguely supposing that it was there ‘always.’ But suppose that what he had found at his foot was not a stone but a watch and that he now saw such an instrument for the first time. He would then certainly have not been so easily contented with an answer to the riddle of its existence. He would, if he examined it minutely, have observed that it was a structure intended for a certain purpose, and having all its parts arranged for that object, and mutually interdependent The different substances of which it was composed would be discovered to have each its special appropriateness for the fulfilling of some particular function in the economy of the whole. Though unacquainted with watches he would, if he was a man of sense and cultivation, infallibly conclude that he had before him an instrument intelligently constructed with a certain object in view—the object of measuring the flight of time. He would feel assured of this, even though he should find that the object of the mechanism were not attained with absolute accuracy, and even though there were some parts of it whose functions were not clear to him. The watch would be rightly regarded as a work of design; and the observer would be justified in arguing from it to the existence of a designer, endowed with the faculties of intelligence and conscious purpose, by whom the watch must have been put together.

The rest of Paley’s Natural Theology is an application of this analogy to the question of the origin of the universe. Ranging over the whole field of animate and inanimate nature he points to instance after instance of what appears to be the minute and thoughtful adaptation of means to ends, the co-ordination of part with part in the interest of the whole, and he has no difficulty, from this point of view, in showing the world of nature to be a piece of mechanism far more wonderfully and ingeniously constructed than any watch, and bearing prima facie evidence of the most convincing kind of its construction by a Being possessed of intelligence, purpose and foresight precisely resembling those attributes as displayed by man, but vastly heightened and enlarged. As the watch must have been made by man, so a manlike being, endowed with the necessary powers and faculties, must be postulated as the maker of the material universe. And thus the existence of a God made in the image of man appeared to have been demonstrated to the satisfaction of eighteenth-century theology.

But minds of real philosophic depth have always shrunk from pressing home deductions of this sort. They have felt that the matter is probably not quite so simple as it might appear on the surface, and they have recognised that if one is allowed to argue from the phenomena of nature to the qualities of the author of nature one cannot draw an arbitrary line including only those facts which testify to wisdom, power and goodness, and excluding from view all those which reveal imperfection of design and execution, or which would convict a man, if he were their author, of inhumanity and injustice. If the universe is really analogous to a watch one is entitled to examine it throughout as one would examine a watch. All watches testify to intelligence and design, but besides good watches there are bad ones, there are those which are made of cheap materials, rudely put together, with showy exteriors and unreliable works. Every watch, if examined by experts in mechanism, in art, and so forth, would reveal the characteristics of its designer and maker, and these characteristics would not always be admirable. They would rarely, in fact, be altogether admirable. If we apply these methods of inquiry to a universe which contains malarial mosquitoes, slave-making ants, snakes, earthquakes, and all the pests which blight and deform life without calling forth any strong or noble qualities to carry on the contest with them, we shall go where Paley certainly never intended to lead us, but we shall go there by Paley’s road. The fact is that these methods are altogether fantastic and inapplicable. The universe is not made like a watch. When we observe a human being or one of the higher animals we say, ‘He has such and such qualities; he is faithful, false, brave, cowardly, diligent, indolent, strong, weak, beautiful or ugly,’ but we do not think of referring his qualities back to certain attributes of an unknown maker of his physical and mental organism. A philosophy worthy of the name has always tended to regard the world as in some sense a vital organism, and has asked ‘What is it?’ rather than ‘What does it prove about some other being?’ “How green must be the maker of all grass” was quite a legitimate satire on all such attempts to deduce the qualities of a hypothetical creator from the phenomena of the universe. Thus the mistake of Paley and his school was fundamental. It was the mistake of seeking God in fragmentary phenomena—the same mistake, essentially, as that rebuked by Christ, by which every calamity or material blessing is regarded as a ‘judgment’ or a reward. His method, if applied with thorough-going consistency, destroys its own basis, for the One and the Many, the Whole and the Parts, cannot be apprehended at one and the same time by one and the same faculty of any human mind. Looking at phenomena alone, and thinking in that sphere, we cannot say that God made the world but rather that the world is becoming divine. Philosophically and religiously, God is all in all—historically, He is not the beginning, He is rather the end, the end in which the whole history is resumed.

Paley’s elaborate argument was felt by the orthodox of his time to be called for, even though at this period his way of thinking was popular. The conception of the world as a vital organism was as yet, indeed, very vague, and unsupported by any detailed, scientific scrutiny of the facts of nature, but it was in the air—it had always been in the air; it always held the minds of cautious students back from a complete surrender to the facile but illusory way of thinking typified by Paley’s famous analogy of the universe and the watch. Bacon knew that species could be transformed by the action of a new environment.4 Goethe had a clear conception of the evolution theory, based on a study of organic structure. Erasmus Darwin, in 1794, had uttered the great and final word: “The world has been generated rather than created.”5 Lamarck’s Philosophie Zoologique was not published till 1809, nine years after Paley’s Natural Theology, but his conception of the development of special characteristics by habitual exercise and their transmission by inheritance had been freely mooted in Paley’s day, for Paley frequently takes occasion to combat it. Even the conception of natural selection as an agency in the formation of types of being may be traced in a fantastic form as far back as to Empedocles,6 while Plato, or whoever composed a striking couplet attributed to him in the Greek Anthology, had divined the plasticity of natural forms. “Time,” he wrote, “sways the whole world; time has power in its prolonged lapse to change the names and shapes, the nature and the destiny of things.”7

Fifty years after the appearance of Paley’s work, the grandson of Erasmus Darwin wrote ‘No thoroughfare’ on the entrance to Paley’s line of speculation, and closed it to mankind for ever. He did this in two ways—first by marshalling from his studies of comparative anatomy and of embryology an extraordinary volume of convincing evidence for the fact of the mutability of natural forms, and secondly by his attempt to establish a plausible method by which the change and development of organs and types might actually have taken place. The method, summed up in the phrases ‘natural selection’ and ‘survival of the fittest,’ was what really caught the attention of the world, and gave his doctrine the wings which carried it into almost every sphere of human thought. However we take it, it was certainly an immense contribution to the organization of knowledge, but whether it is really what it first seemed to be, the basic fact at the bottom of all the phenomena of evolution, is coming to look more and more doubtful in the light of later researches.8

This question will have to be considered later on in the course of this study, and in relation to its main inquiry, which is this: What precisely was the change in philosophic and religious outlook brought about by the full and final establishment of the doctrine of evolution? Where has evolution left the argument from design? Must we study nature as a mass of unrelated phenomena, or can we discern, through these, any fundamental unity to which they stand in organic relation; and if we can, what is the nature of this unity?

It will be useful in the first place to have before us a typical specimen of Paley’s method. I shall choose as an example the case which he considered so striking that he deemed it almost sufficient in itself to bear the whole weight of his argument In his ninth chapter, ‘On the Muscles,’ he writes:—

“The next circumstance which I shall mention under this head of muscular arrangement is so decisive a mark of intention, that it always appeared to me to supersede, in some measure, the necessity of seeking for any other observation upon the subject; and that circumstance is, the tendons which pass from the leg to the foot being bound down by a ligament to the ankle. The foot is placed at a considerable angle with the leg. It is manifest, therefore, that flexible strings, passing along the interior of the angle, if left to themselves, would, when stretched, start from it. The obvious preventive is to tie them down. And this is done, in fact. Across the instep, or rather just above it, the anatomist finds a strong ligament, under which the tendons pass to the foot. The effect of the ligament as a bandage can be made evident to the senses; for if it be cut, the tendons start up. The simplicity, yet the clearness of this contrivance, its exact resemblance to established resources of art, place it amongst the most indubitable manifestations of design with which we are acquainted. “There is also a further use to be made of the present example, and that is, as it precisely contradicts the opinion that the parts of animals may have been formed by what is called appetency, i.e. endeavour perpetuated and imperceptibly working its effect through an incalculable series of generations. We have here no endeavour but the reverse of it—a constant renitency and reluctance. The endeavour is all the other way. The pressure of the ligament constrains the tendons; the tendons react upon the pressure of the ligament. It is impossible that the ligament should ever have been generated by the exercise of the tendon, or in the course of that exercise, forasmuch as the force of the tendon perpendicularly resists the fibre, which confines it, and is constantly endeavouring not to form, but to rupture and displace, the threads of which the ligament is composed.”

Paley’s account of the function of the annular ligament at the ankle is correct, and strikingly put. A similar ligament occurs at the wrist, and navvies who have hard muscular work to do in digging and shovelling are wont to reinforce this ligament and to keep it from rupture by a leather strap round the wrist. The strap performs exactly the same function as the ligament, and from Paley’s point of view one is as artificial, as much a ‘contrivance,’ as the other. But his point of view is wrong. He conceives the Creator as having at his disposal fully formed elements or materials—sinews, bones, ligaments, and the like—and assembling them into a working mechanism. In fact, however, none of these things is now what it was originally—time, as Plato says, has changed its “name and shape.” The annular ligaments are recognized by modern anatomists as having originated in special thickenings of the fascial sheaths of the adjoining muscles of the wrist and ankle. They had a function which was not originally connected with keeping down the long tendons that run along the interior angle of the leg and foot. Contractility, as biologists tell us, is a fundamental property of living protoplasm; and it is easy to imagine that, at the very beginning of the formation of muscular structure and bone articulation, two lines of contractile force might cross each other and thus permit the gradual evolution of the present arrangement, nature continually visiting with disability and extinction those individuals in whom the resisting power of the muscles which were eventually to form the annular ligament was unduly feeble, and giving a better chance of life, and of the propagation of their kind, to those in whom it was strong. The instance, in fact, is one of those in which the explanation of development by natural selection is most obvious and plausible.

In his second paragraph Paley touches on the theory of “appetency,” the supposed tendency of natural structure to alter and adapt itself on the lines indicated by the actual exercise of function, and in consequence of that exercise. This is practically the theory since identified with the name of Lamarck. Paley scarcely does it justice, for no Lamarckian would suggest that a muscle could, in the course of its exercise, develop the ligament whose function is to restrain it. The ligament would be developed by its own exercise. But as Lamarckism will be discussed later on, the issue as between these rival theories need not be debated here.

Let us set beside Paley’s argument on the annular ligament of the ankle a passage from a modern scientific work, Strasburger’s Text Book of Botany. It will introduce us, from the side of the strictest scientific observation and of the fullest acceptance of the evolution theory, to the same kind of problems as those discussed in Paley’s Natural Theology, and it will raise in a very distinct and unevadable fashion the question, what we are to think of the power manifested in the operations of Nature. In the introduction to his work, in which Dr. Strasburger had associated with him three other eminent German botanists, we find the following remarkable passage dealing with circumstances observed to exist in the ‘phylogenetic’ or tribal (as opposed to the ‘ontogenetic’ or individual) history of plant species:—

“Although the great importance of natural selection in the development of the organic world has been fully recognised by most naturalists, the objection has been raised that it alone is not a sufficient explanation of all the different processes in the phylogeny of an organism. Attention has been called to such organs as would be incapable of exercising their function until in an advanced stage of development, and so could not originally have been of any advantage in a struggle for existence. How could natural selection tend to develop an organ which would be useless so long as it was still in a rudimentary condition? This objection has led to the supposition of an internal force residing in the substance of the organisms themselves and controlling their development in certain definite directions. Many naturalists indeed have gone so far as to affirm that only the less advantageous qualities have been affected by the struggle for existence, while the more advantageous have been uninfluenced by it”9

One can easily imagine what a modern Paley bent on reconciling orthodoxy and evolution would say to this. He would cry, Design, forethought, intelligence—here is the clearest evidence of it! And indeed there are many modern biologists who do not shrink from the admission that the processes of nature must ultimately be interpreted in terms of will or intention, not in terms of chance or blind mechanism. Thus, to the Darwinian argument that organs can be and are, demonstrably, formed by gradual adaptation to surrounding conditions without assuming the necessity of purposeful design, it is often replied that the very fact of adaptability is itself one of the strongest evidences if not of design at least of purpose. And J. v. Uexküll, who describes life as consisting essentially in the fact that it proceeds according to design (planmässig), has the following remarkable passage in his Experimental Biology10:—

“When we look backwards, every phase in the process of development seems to us to have proceeded in a strictly causal manner from physico-chemical processes. But when we turn to look forward, it is certain that the physico-chemical processes if left to their own causality must immediately bring about the destruction of the organism. In fact, the clearest definition we can give of dying is to say of an organism that its processes now go on no longer teleologically (zweckmässig) but only causally.”11

Yet the modern Paley would be rash in arguing from facts like these (supposing them fully established) to the conscious, intelligent contrivance of a single foreseeing Mind. For very few things in this universe appear to be done as a presiding, conscious intelligence would do them. Conscious intelligence would not have evolved the giant armadillo only that the whole species might be destroyed by the sabre-toothed tiger, and would not have armed the sabre-toothed tiger for the attack on the armadillo in such a way that when he had exterminated the victim-species the formation of his teeth rendered it impossible for him to prey on any other animal.12 Conscious intelligence would not have allowed the relic of a disused organ, in the shape of the vermiform appendix, to be a constant source of danger and suffering to countless generations of men—danger against which no exercise of prudence or energy can secure them.

Let us examine a couple of other crucial cases. The embryo of every mammalian animal is prepared in the womb for the life it is to live under wholly different conditions. Lungs are formed when there is no air for them to breathe, eyes when there is no light, a digestive system when nourishment is derived as yet direct from the mother’s blood. This capacity for anticipatory development during a period of gestation or incubation becomes absolutely necessary for the maintenance of life as soon as animals, ceasing to multiply by merely dividing in two, become more highly organized and have to devote special germ-cells to reproductive purposes. Here is certainly purpose, or, as I should prefer to call it, directivity—here we recognize what Reinke calls the X-factor in nature. But conscious, intelligent contrivance? We must recollect how many of these embryos are destined to perish at birth or before attaining any appreciable degree of independent life. Would not intelligence foresee that, and bring to birth only what was destined to endure?

Again, there are certain species of butterflies which have put on a coloration and a form the effect of which is to aid them in evading the attacks of birds. They were not created so; they have become so; and the precise manner of the becoming will be fully discussed in a later chapter. Let us assume for the moment that this adaptation did not occur by a series of lucky accidents or by any merely mechanical process. Are we, then, bound to attribute it to intelligent contrivance? The question will be best answered by simply putting a case which admits of no doubt. Suppose there were an island in which there were no birds, except such as prey on fishes or on each other, but never on insects. The butterflies on this island, if there were any, would certainly show no trace of protective form or coloration. But at some time or other insect-eating birds might be introduced to the island, as the English sparrow has been introduced in Australia. Then, if the extermination of the butterflies did not proceed too rapidly, we might expect, in the course of generations, to see protective adaptations assumed. But could we expect to see them assumed in anticipation of the advent of the destroyers? We could not. Naturalists, however much they may differ, as they do differ, upon the question as to how protective adaptations actually take place, would all agree that they could not possibly take place in anticipation of needs not yet present. If they did, we should have a miracle, and where miracle comes in knowledge goes out. The cases where conscious, intelligent contrivance would be unmistakably recognizable are just the cases which never occur. The signal service rendered by the champions of the evolution theory,