Volume I Part 12 (1/2)
We may now proceed to consider certain misconceptions of the Darwinian theory which are largely, not to say generally, prevalent among supporters of the theory. These misconceptions, therefore, differ from those which fall to be considered in the next chapter, i. e.
misconceptions which const.i.tute grounds of objection to the theory.
Of all the errors connected with the theory of natural selection, perhaps the one most frequently met with--especially among supporters of the theory--is that of employing the theory to explain all cases of phyletic modification (or inherited change of type) indiscriminately, without waiting to consider whether in particular cases its application is so much as logically possible. The term ”natural selection” thus becomes a magic word, or Sesame, at the utterance of which every closed door is supposed to be immediately opened. Be it observed, I am not here alluding to that merely blind faith in natural selection, which of late years has begun dogmatically to force this principle as the sole cause of organic evolution in every case where it is _logically possible_ that the principle can have come into play. Such a blind faith, indeed, I hold to be highly inimical, not only to the progress of biological science, but even to the true interests of the natural selection theory itself. As to this I shall have a good deal to say in the next volume.
Here, however, the point is, that the theory in question is often invoked in cases where it is not even logically possible that it can apply, and therefore in cases where its application betokens, not merely an error of judgment or extravagance of dogmatism, but a fallacy of reasoning in the nature of a logical contradiction. Almost any number of examples might be given; but one will suffice to ill.u.s.trate what is meant. And I choose it from the writings of one of the authors of the selection theory itself, in order to show how easy it is to be cheated by this mere juggling with a phrase--for of course I do not doubt that a moment's thought would have shown the writer the untenability of his statement.
In his most recent work Mr. Wallace advances an interesting hypothesis to the effect that differences of colour between allied species, which are apparently too slight to serve any other purpose, may act as ”recognition marks,” whereby the opposite s.e.xes are enabled at once to distinguish between members of their own and of closely resembling species. Of course this hypothesis can only apply to the higher animals; but the point here is that, supposing it to hold for them, Mr. Wallace proceeds to argue thus:--Recognition marks ”have in all probability been acquired in the process of differentiation for the purpose of checking the intercrossing of allied forms,” because ”one of the first needs of a new species would be to keep separate from its nearest allies, and this could be more readily done by some easily seen external mark[32].”
Now, it is clearly not so much as logically possible that these recognition-marks (supposing them to be such) can have been acquired by natural selection, ”for the purpose of checking intercrossing of allied forms.” For the theory of natural selection, from its own essential nature as a theory, is logically exclusive of the supposition that survival of the fittest ever provides changes in antic.i.p.ation of future uses. Or, otherwise stated, it involves a contradiction of the theory itself to say that the colour-changes in question were originated by natural selection, in order to meet ”one of the _first_ needs of a _new_ species,” or for the purpose of _subsequently_ preventing intercrossing with allied forms. If it had been said that these colour-differentiations were originated by some cause other than natural selection (or, if by natural selection, still with regard to some _previous_, instead of _prophetic_, ”purpose”), and, when so ”acquired,”
_then_ began to serve the ”purpose” a.s.signed, the argument would not have involved the fallacy which we are now considering. But, as it stands, the argument reverts to the teleology of pre-Darwinian days--or the hypothesis of a ”purpose” in the literal sense which sees the end from the beginning, instead of a ”purpose” in the metaphorical sense of an adaptation that is evolved by the very modifications which subserve it[33].
[32] _Darwinism_, pp. 218 and 227.
[33] Since the above was written Prof. Lloyd Morgan has published a closely similar notice of the pa.s.sage in question. ”This language,”
he says, ”seems to savour of teleology (that pitfall of the evolutionist). The cart is put before the horse. The recognition-marks were, I believe, not produced to prevent intercrossing, but intercrossing has been prevented because of preferential mating between individuals possessing special recognition-marks. To miss this point is to miss an important segregation-factor.”--(_Animal Life and Intelligence_, p. 103.) Again, on pp. 184-9, he furnishes an excellent discussion on the whole subject of the fallacy alluded to in the text, and gives ill.u.s.trative quotations from other prominent Darwinians. I should like to add that Darwin himself has nowhere fallen into this, or any of the other fallacies, which are mentioned in the text.
Another very prevalent, and more deliberate, fallacy connected with the theory of natural selection is, _that it follows deductively from the theory itself_ that the principle of natural selection must be the sole means of modification in all cases where modification is of an _adaptive_ kind,--with the consequence that no other principle can ever have been concerned in the production of structures or instincts which are of any use to their possessors. Whether or not natural selection actually has been the sole means of adaptive modification in the race, as distinguished from the individual, is a question of biological fact[34]; but it involves a grave error of reasoning to suppose that this question can be answered deductively from the theory of natural selection itself, as I shall show at some length in the next volume.
[34] Of course adaptive modifications produced in the individual lifetime, and not _inherited_, do not concern the question at all.
In this and the following paragraphs, therefore, ”adaptations,”
”adaptive modifications,” &c., refer exclusively to such as are hereditary, i. e. phyletic.
A still more extravagant, and a still more unaccountable fallacy is the one which represents it as following deductively from the theory of natural selection itself, that all _hereditary_ characters are ”necessarily” due to natural selection. In other words, not only all adaptive, but likewise all non-adaptive hereditary characters, it is said, _must_ be due to natural selection. For non-adaptive characters are taken to be due to ”correlation of growth,” in connexion with some of the adaptive ones--natural selection being thus the _indirect_ means of producing the former _wherever_ they may occur, on account of its being the _direct_ and the _only_ means of producing the latter. Thus it is deduced from the theory of natural selection itself,--1st, that the principle of natural selection is the only possible cause of adaptive modification: 2nd, that non-adaptive modifications can only occur in the race as correlated appendages to the adaptive: 3rd, that, consequently, natural selection is the only possible cause of modification, whether adaptive or non-adaptive. Here again, therefore, we must observe that none of these sweeping generalizations can possibly be justified by deductive reasoning from the theory of natural selection itself. Any attempt at such deductive reasoning must necessarily end in circular reasoning, as I shall likewise show in the second volume, where this whole ”question of utility” will be thoroughly dealt with.
Once more, there is an important oversight very generally committed by the followers of Darwin. For even those who avoid the fallacies above mentioned often fail to perceive, that natural selection can only begin to operate if the _degree_ of adaptation is already given as sufficiently high to count for something in the struggle for _existence_. Any adaptations which fall below this level of importance cannot possibly have been produced by survival of the fittest. Yet the followers of Darwin habitually speak of adaptative characters, which _in their own opinion_ are subservient merely to comfort or convenience, as having been produced by such means. Clearly this is illogical; for it belongs to the essence of Darwin's theory to suppose, that natural selection can have no jurisdiction beyond the line where structures or instincts already present a sufficient degree of adaptational value to increase, in some measure, the expectation of life on the part of their possessors. We cannot speak of adaptations as due to natural selection, without thereby affirming that they present what I have elsewhere termed a ”selection value.”
Lastly, as a mere matter of logical definition, it is well-nigh self-evident that the theory of natural selection is a theory of the origin, and c.u.mulative development, of _adaptations_, whether these be distinctive of species, or of genera, orders, families, cla.s.ses, and sub-kingdoms. It is only when the adaptations happen to be distinctive of the first (or lowest) of these taxonomic divisions, that the theory which accounts for _these_ adaptations accounts also for the forms which present them,--i. e. becomes _also_ a theory of the origin of species.
This, however, is clearly but an accident of particular cases; and, therefore, even in them the theory is _primarily_ a theory of adaptations, while it is but secondarily a theory of the species which present them. Or, otherwise stated, the theory is no more a theory of the origin of species than it is of the origin of genera, families, and the rest; while, on the other hand, it is _everywhere_ a theory of the adaptive modifications whereby each of these taxonomic divisions has been differentiated as such. Yet, sufficiently obvious as the accuracy of this definition must appear to any one who dispa.s.sionately considers it, several naturalists of high standing have denounced it in violent terms. I shall therefore have to recur to the subject at somewhat greater length hereafter. At present it is enough merely to mention the matter, as furnis.h.i.+ng another and a curious ill.u.s.tration of the not infrequent weakness of logical perception on the part of minds well gifted with the faculty of observation. It may be added, however, that the definition in question is in no way hostile to the one which is virtually given by Darwin in the t.i.tle of his great work. _The Origin of Species by means of Natural Selection_ is beyond doubt the best t.i.tle that could have been given, because at the time when the work was published the _fact_, no less than the _method_, of organic evolution had to be established; and hence the most important thing to be done at that time was to prove the trans.m.u.tation of species. But now that this has been done to the satisfaction of naturalists in general, it is as I have said, curious to find some of them denouncing a wider definition of the principle of natural selection, merely because the narrower (or included) definition is invested with the charm of verbal a.s.sociations[35].
[35] The question as to whether natural selection has been the only principle concerned in the origination of species, is quite distinct from that as to the accuracy of the above definition.
So much for fallacies and misconceptions touching Darwin's theory, which are but too frequently met with in the writings of its supporters. We must now pa.s.s on to mention some of the still greater fallacies and misconceptions which are prevalent in the writings of its opponents.
And, in order to do this thoroughly, I shall begin by devoting the remainder of the present chapter to a consideration of the antecedent standing of the two theories of natural selection and supernatural design. This having been done, in the succeeding chapters I shall deal with the evidences for, and the objections against, the former theory.
Beginning, then, with the antecedent standing of these alternative theories, the first thing to be noticed is, that they are both concerned with the same subject-matter, which it is their common object to explain. Moreover, this subject-matter is clearly and sharply divisible into two great cla.s.ses of facts in organic nature--namely, those of Adaptation and those of Beauty. Darwin's theory of descent explains the former by his doctrine of natural selection, and the latter by his doctrine of s.e.xual selection. In the first instance, therefore, I shall have to deal only with the facts of adaptation, leaving for subsequent consideration the facts of beauty.
Innumerable cases of the adaptation of organisms to their surroundings being the facts which now stand before us to be explained either by natural selection or by supernatural intention, we may first consider a statement which is frequently met with--namely, that even if all such cases of adaptation were proved to be fully explicable by the theory of descent, this would const.i.tute no disproof of the theory of design: all the cases of adaptation, it is argued, might still be due to design, even though they admit of being hypothetically accounted for by the theory of descent. I have heard an eminent Professor tell his cla.s.s that the many instances of mechanical adaptation discovered and described by Darwin as occurring in orchids, seemed to him to furnish better proof of supernatural contrivance than of natural causes; and another eminent Professor has informed me that, although he had read the _Origin of Species_ with care, he could see in it no evidence of natural selection which might not equally well have been adduced in favour of intelligent design. But here we meet with a radical misconception of the whole logical att.i.tude of science. For, be it observed, this exception _in limine_ to the evidence which we are about to consider does not question that natural selection _may_ be able to do all that Darwin ascribes to it. The objection is urged against his interpretation of the facts merely on the ground that these facts might _equally well_ be ascribed to intelligent design. And so undoubtedly they might, if we were all simple enough to adopt a supernatural explanation whenever a natural one is found sufficient to account for the facts. Once admit the irrational principle that we may a.s.sume the operation of higher causes where the operation of lower ones is sufficient to explain the observed phenomena, and all our science and all our philosophy are scattered to the winds.
For the law of logic which Sir William Hamilton called the law of parsimony--or the law which forbids us to a.s.sume the operation of higher causes when lower ones are found sufficient to explain the observed effects--this law const.i.tutes the only barrier between science and superst.i.tion. It is always possible to give a hypothetical explanation of any phenomenon whatsoever, by referring it immediately to the intelligence of some supernatural agent; so that the only difference between the logic of science and the logic of superst.i.tion consists in science recognising a validity in the law of parsimony which superst.i.tion disregards. Therefore one can have no hesitation in saying that this way of looking at the evidence in favour of natural selection is not a scientific or a reasonable way of looking at it, but a purely superst.i.tious way. Let us take, as an ill.u.s.tration, a perfectly parallel case. When Kepler was unable to explain by any known causes the paths described by the planets, he resorted to a supernatural explanation, and supposed that every planet was guided in its movements by some presiding angel. But when Newton supplied a beautifully simple physical explanation, all persons with a scientific habit of mind at once abandoned the metaphysical one. Now, to be consistent, the above-mentioned Professors, and all who think with them, ought still to adhere to Kepler's hypothesis in preference to Newton's explanation; for, excepting the law of parsimony, there is certainly no other logical objection to the statement, that the movements of the planets afford as good evidence of the influence of guiding angels as they do of the influence of gravitation.
So much, then, for the illogical position that, granting the evidence in favour of natural descent and supernatural design to be equal and parallel, we should hesitate in our choice between the two theories.