Here is an interesting essay on design by Darwin’s contemporary John Stuart Mill. Question: are the molecular machines that Michael Behe identified as decisive evidence for design merely analogous to human-built machines or do they fully instantiate the concept of machine? Another question: Why should knowing the mode of implementation of design be so important to detecting its presence? If, for instance, biological designs vastly exceed human designs in technological sophistication, so that our current technology is incapable of grasping their implementation, why should that undercut our ability nonetheless to recognize their design?
John Stuart Mill
The Argument from Marks of Design in Nature
We now at last reach an argument of a really scientific character, which does not shrink from scientific tests, but claims to be judged by the established canons of Induction. The Design argument is wholly grounded on experience. Certain qualities, it is alleged, are found to be characteristic of such things as are made by an intelligent mind for a purpose. The order of nature of Nature, or some considerable parts of it, exhibit these qualities in a remarkable degree. We are entitled, from this great similarity in the effects, to infer similarity in the cause, and to believe that things which it is beyond the power of man to make, but which resemble the works of man in all but power, must also have been made by Intelligence, armed with a power greater than human.
I have stated this argument in its fullest strength, as it is stated by its most thoroughgoing assertors. A very little consideration, however, suffices to show that though it has some force, its force is very generally overrated. PaleyÃ¢â‚¬â„¢s illustration of a watch puts the case much too strongly. If I found a watch on an apparently desolate island, I should indeed infer that it had been left there by a human being; but the inference would not be from marks of design, but because I already knew by direct experience that watches are made by men. I should draw the inference no less confidently from a foot print, or from any relic however insignificant which experience has taught me to attribute to man: as geologists infer the past existence of animals from coprolites, though no one sees marks of design in a coprolite. The evidence of design in creation can never reach the height of direct induction; it amounts only to the inferior kind of inductive evidence called analogy. Analogy agrees with induction in this, that they both argue that a thing known to resemble another in certain circumstances (call those circumstances A and B) will resemble it in another circumstance (call it C). But the difference is that in induction, A and B are known, by a previous comparison of many instances, to be the very circumstances on which C depends, or with which it is in some way connected. When this has not been ascertained, the argument amounts only to this, that since it is not known with which of the circumstances existing in the known case C is connected, they may as well be A and B as any others; and therefore there is a greater probability of C in cases where we know that A and B exist, than in cases of which we know nothing at all. This argument is of a weight very difficult to estimate at all, and impossibly to estimate precisely. It may be very strong, when the known points of agreement, A and B &c. are numerous and the known points of difference few; or very weak, when the reverse is the case: but it can never be equal in validity to a real induction. The resemblances between some of the arrangements in nature and some of those made by man are considerable, and even as mere resemblances afford a certain presumption of similarity of cause: but how great that presumption is, it is hard to say. All that can be said with certainty is that these likenesses make creation by intelligence considerably more probably than if the likenesses had been less, or than if there had been no likenesses at all.
This mode, however, of stating the case does not do full justice to the evidence of Theism. The Design argument is not drawn from mere resemblances in Nature to the works of human intelligence, but from the special character of those resemblances. The circumstances in which it is alleged that the world resembles the works of man are not circumstances taken at random, but are particular instances of a circumstance which experience shows to have a real connection with an intelligent origin, the fact of conspiring to an end. The argument therefore is not one of mere analogy. As mere analogy it has its weight, but it is more than analogy. It surpasses analogy exactly as induction surpasses it. It is an inductive argument.
This, I think, is undeniable, and it remains to test the argument by the logical principles applicable to Induction. For this purpose it will be convenient to handle, not the argument as a whole, but some one of the most impressive cases of it, such as the structure of the eye, or of the ear. It is maintained that the structure of the eye proves a designing mind. To what class of inductive arguments does this belong? and what is its degree of force?
The species of inductive arguments are four in number, corresponding to the four Inductive Methods; the Methods of Agreement, of Difference, of Residues, and of Concomitant Variations. The argument under consideration falls within the first of these divisions, the Method of Agreement. This is, for reasons known to inductive logicians, the weakest of the four, but the particular argument is a strong one of the kind. It may be logically analysed as follows:
The parts of which the eye is composed, and the collocations which constitute the arrangement of those parts, resemble one another in this very remarkable property, that they all conduce to enabling the animal to see. These things being as they are, the animal sees: if any one of them were different from what it is, the animal, for the most part, would either not see, or would not see equally well. And this is the only marked resemblance that we can trace among the different parts of this structure, beyond the general likeness of composition and organization which exists among all other parts of the animal. Now the particular combination of organic elements called an eye had, in every instance, a beginning in time and must therefore have been brought together by a cause or causes. The number of instances is immeasurably greater than is, by the principles of inductive logic, required for the exclusion of a random concurrence of independent causes, or speaking technically, for the elimination of chance. We are therefore warranted by the canons of induction in concluding that what brought all these elements together was some cause common to them all; and inasmuch as the elements agree in the single circumstance of conspiring to produce sight, there must be some connection by way of causation between the cause which brought those elements together, and the fact of sight.
This I conceive to be a legitimate inductive inference, and the sum and substance of what Induction can do for Theism. The natural sequel of the argument would be this. Sight, being a fact not precedent but subsequent to the putting together of the organic structure of the eye, can only be connected with the production of that structure in the character of a final, not an efficient cause; that is, it is not Sight itself but an antecedent Idea of it, that must be the efficient cause. But this at once marks the origin as proceeding from an intelligent will.
I regret to say, however, that this latter half of the argument is not so inexpugnable as the former half. Creative forethought is not absolutely the only link by which the origin of the wonderful mechanism of the eye may be connected with the fact of sight. There is another connecting link on which attention has been greatly fixed by recent speculations, and the reality of which cannot be called in question, though its adequacy to account for such truly admirable combinations as some of those in Nature, is still and will probably long remain problematical. This is the principle of Ã¢â‚¬Å“the survival of the fittest.Ã¢â‚¬Â
This principle does not pretend to account for the commencement of sensation or of animal or vegetable life. But assuming the existence of some one or more very low forms of organic life, in which there are no complex adaptations nor any marked appearances of contrivance, and supposing, as experience warrants us in doing, that many small variations from those simple types would be thrown out in all directions, which would be transmissable by inheritance, and of which some would be advantageous to the creature in its struggle for existence and others disadvantageous, the forms which are advantageous would always tend to survive and those which are disadvantageous to perish. And thus there would be a constant though slow general improvement of the type as it branched out into many different varieties, adapting it to different media and modes of existence, until it might possibly, in countless ages, attain to the most advanced examples which now exist.
It must be acknowledged that there is something very startling, and prima facie improbable in this hypothetical history of Nature. It would require us, for example, to suppose that the primaeval animal of whatever nature it may have been, could not see, and had at most such slight preparation for seeing as might be constituted by some chemical action of light upon its cellular structure. One of the accidental variations which are liable to take place in all organic beings would at some time or other produce a variety that could see, in some imperfect manner, and this peculiarity being transmitted by inheritance, while other variations continued to take place in other directions, a number of races would be produced who, by the power of even imperfect sight, would have a great advantage over all other creatures which could not see and would in time extirpate them from all places, except, perhaps, a few very peculiar situations underground. Fresh variations supervening would give rise to races with better and better seeing powers until we might at last reach as extraordinary a combination of structures and functions as are seen in the eye of man and of the more important animals. Of this theory when pushed to this extreme point, all that can now be said is that it is not so absurd as it looks, and that the analogies which have been discovered in experience, favourable to its possibility, far exceed what any one could have supposed beforehand. Whether it will ever be possible to say more than this, is at present uncertain. The theory if admitted would be in no way whatever inconsistent with Creation. But it must be acknowledge that it would greatly attenuate the evidence for it.
Leaving this remarkable speculation to whatever fate the progress of discovery may have in store for it, I think it must be allowed that, in the present state of our knowledge, the adaptations in Nature afford a large balance of probability in favour of creation by intelligence. It is equally certain that this is no more than a probability; and that the various other arguments of Natural Theology which we have considered, add nothing to its force. Whatever ground there is, revelation apart, to believe in an Author of Nature, is derived from the appearances in the universe. Their mere resemblance to the works of man, or to what man could do if he had the same power over the materials of organized bodies which he has over the materials of a watch, is of some value as an argument of analogy: but the argument is greatly strengthened by the properly inductive considerations which establish that there is some connection through causation between the origin of the arrangements of nature and the ends they fulfil; an argument which is in many cases slight, but in others, and chiefly in the nice and intricate combinations of vegetable and animal life, is of considerable strength.