[21] Mental Evolution in Animals, pp. 155-8.
[22] [I have put 'may' in place of 'do' for the sake of argument.—Ed.]
II.
Suppose the man who found the watch upon a heath to continue his walk till he comes down to the sea-shore, and suppose further that he is as ignorant of physical geography as he is of watch-making. He soon begins to observe a number of adaptations of means to ends, which, if less refined and delicate than those that formed the object of his study in the watch, are on the other hand much more impressive from the greatly larger scale on which they are displayed. First, he observes that there is a beautiful basin hollowed out in the land for the reception of a bay; that the sides of this basin, which from being near its opening are most exposed to the action of large rolling billows, are composed of rocky cliffs, evidently in order to prevent the further encroachment of the sea, and the consequent destruction of the entire bay; that the sides of the basin, which from being successively situated more inland are successively less and less exposed to the action of large waves, are constituted successively of smaller rocks, passing into shingle, and eventually into the finest sand: that as the tides rise and fall with as great a regularity as was exhibited by the movements of the watch, the stones are carefully separated out from the sand to be arranged in sloping layers by themselves, and this always with a most beautiful reference to the places round the margin of the basin which are most in danger of being damaged by the action of the waves. He would further observe, upon closer inspection, that this process of selective arrangement goes into matters of the most minute detail. Here, for instance, he would observe a mile or two of a particular kind of seaweed artistically arranged in one long sinuous line upon the beach; there he would see a wonderful deposit of shells; in another place a lovely little purple heap of garnet sand, the minute particles of which have all been carefully picked out from the surrounding acres of yellow sand. Again, he would notice that the streams which come down to the bay are all flowing in channels admirably dug out for the purpose; and, being led by curiosity to investigate the teleology of these various streams, he would find that they serve to supply the water which the sea loses by evaporation, and also, by a wonderful piece of adjustment, to furnish fresh water to those animals and plants which thrive best in fresh water, and yet by their combined action to carry down sufficient mineral constituents to give that precise degree of saltness to the sea as a whole which is required for the maintenance of pelagic life. Lastly, continuing his investigations along this line of inquiry, he would find that a thousand different habitats were all thoughtfully adapted to the needs of a hundred thousand different forms of life, none of which could survive if these habitats were reversed. Now, I think that our imaginary inquirer would be a dull man if, as the result of all this study, he failed to conclude that the evidence of Design furnished by the marine bay was at least as cogent as that which he had previously found in his study of the watch.
But there is this great difference between the two cases. Whereas by subsequent inquiry he could ascertain as a matter of fact that the watch was due to intelligent contrivance, he could make no such discovery with reference to the marine bay: in the one case intelligent contrivance as a cause is independently demonstrable, while in the other case it can only be inferred. What, then, is the value of the inference?
If, after the studies of our imaginary teleologist had been completed, he were introduced to the library of the Royal Society, and if he were then to spend a year or two in making himself acquainted with the leading results of modern science, I fancy that he would end by being both a wiser and a sadder man. At least I am certain that in learning more he would feel that he is understanding less—that the archaic simplicity of his earlier explanations must give place to a matured perplexity upon the whole subject. To begin with, he would now find that every one of the adjustments of means to ends which excited his admiration on the sea-coast were due to physical causes which are perfectly well understood. The cliffs stood at the opening of the bay because the sea in past ages had encroached upon the coast-line until it met with these cliffs, which then opposed its further progress; the bay was a depression in the land which happened to be there when the sea arrived, and into which the sea consequently flowed; the successive occurrence of rocks, shingle, and sand was due to the actions of the waves themselves; the segregation of sea-weeds, shells, pebbles, and different kinds of sand, was due to their different degrees of specific gravity; the fresh-water streams ran in channels because they had themselves been the means of excavating them; and the multitudinous forms of life were all adapted to their several habitats simply because the unsuited forms were not able to live in them. In all these cases, therefore, our teleologist in the light of fuller knowledge would be compelled to conclude at least this much—that the adaptations which he had so greatly admired when he supposed that they were all due to contrivance in anticipation of the existing phenomena, cease to furnish the same evidence of intelligent design when it is found that no one of them was prepared beforehand by any independent or external cause.
He would therefore be led to conclude that if the teleological interpretation of the facts were to be saved at all, it could only be so by taking a much wider view of the subject than was afforded by the particular cases of apparent design which at first appeared so cogent. That is to say, he would feel that he must abandon the supposition of any special design in the construction of that particular bay, and fall back upon the theory of a much more general design in the construction of one great scheme of Nature as a whole. In short he would require to dislodge his argument from the special adjustments which in the first instance appeared to him so suggestive, to those general laws of Nature which by their united operation give rise to a cosmos as distinguished from a chaos.
Now I have been careful thus to present in all its more important details an imaginary argument drawn from inorganic nature, because it furnishes a complete analogy to the actual argument which is drawn from organic nature. Without any question, the instances of apparent design, or of the apparently intentional adaptation of means to ends, which we meet with in organic nature, are incomparably more numerous and suggestive than anything with which we meet in inorganic nature. But if once we find good reason to conclude that the former, like the latter, are all due, not to the immediate, special and prospective action of a contriving intelligence (as in watch-making or creation), but to the agency of secondary or physical causes acting under the influence of what we call general laws, then it seems to me that no matter how numerous or how wonderful the adaptations of means to ends in organic nature may be, they furnish one no other or better evidence of design than is furnished by any of the facts of inorganic nature.
For the sake of clearness let us take any special case. Paley says, 'I know of no better method of introducing so large a subject than that of comparing a single thing with a single thing; an eye, for example, with a telescope.' He then goes on to point out the analogies between these two pieces of apparatus, and ends by asking, 'How is it possible, under circumstances of such close affinity, and under the operation of equal evidence, to exclude contrivance in the case of the eye, yet to acknowledge the proof of contrivance having been employed, as the plainest and clearest of all propositions in the case of the telescope?'