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organisms, a divergence into novelty must needs be inferred on à priori grounds, from the existence of the simple and uniform, and the necessity of adaptation to altered external conditions. But with development in various directions, under the guidance of natural selection, progress is necessarily combined. It is one of the greatest services rendered by the theory of selection, that it has finally broken with the notion of design, which hitherto invested the organic world with perfection externally bestowed, and even in the province of intelligence and morality, where it is said with Schiller,
So grows the Man as grow his greater aims,*
has secured admittance for the uniform method of natural science.
It is highly remarkable how the teleological view of nature could be so long upheld, and is still in part upheld, by theological influence although in the whole organic world we behold a merely relative perfection, and the manifest and multifarious arrangements adverse to design in every grade of organisms, bear a bad testimony to the external directing Power. The perfection exhibited by comparative anatomy, and the estimate of physiological functions is, under all circumstances, the result of adaptation and selection. In the struggle of all against all, those individuals win who in any degree excel their fellows in the division of labour, which, if the direction of activity be altered, often obliges them to disuse organs which were once of service, but in the new conditions are useless, and, it may be generally said, have become injurious.
* Es wächst der Mensch mit seinen grössern Zwecken.
Artificial selection-and here we may speak of design -produces perfection when, by mechanical and physiological labour (the latter especially by means of suitable nutriment), it exercises the particular parts which are to be perfected, and propagates the advantages obtained. What we term natural selection is the epitome of the improvements acquired by specialization in the process of adaptation. The most faithful image of this gradually acquired specialization is afforded by the development of the individual, where from the undifferentiated, by constantly increasing differentiation, the mature animal is evolved in the plenitude of its physiological functions. That in the various animal groups certain grades of perfection are attained, is an uncontroverted fact; but every closer investigation shatters the idol of design. The organism of the bird might induce us to consider it, in the abstract, as modified for the purpose of flight. But if design be allowed to watch over the good flyers, the idea of design must be abandoned with respect to the non-flyers, and, if some idea is indispensable, adaptation must have its due. Herewith the whole theory is broken down, and it will be the same in every other case.
How organic perfection stands with reference to the idea of design, has been acutely and clearly expressed by the author of the "Unconscious" (" Unbewussten"). The theory of descent teaches that there is no independence of the conditions co-operating in an organic phenomenon; rather that its increasing divergence from a common neutral point was an effect of the same causes. The theory of selection makes us acquainted with one of these causes, and unquestionably the most important
as one, which, by purely mechanical compensative phenomena, produces advantageous results. The theory of descent merely casts doubts on the teleological principle by withdrawing the basis for positive proof, but the doctrine of selection sets it directly aside, so far as it is able to extend its explanation. For natural selection in the struggle for existence, the extermination of the less appropriate, and the survival and perpetuation of the fittest and most appropriate, is a process of mechanical causality of which the steady conformity to law is nowhere infringed by any teleological controlling metaphysical principle. This, however, produces a result essentially corresponding to design; that is to say, it naturally bestows on organisms the highest capacity for life under given circumstances. Natural selection solves the apparently insoluble problem of explaining fitness as a result, without calling in the aid of design as a principle.
In each family-for, as we have seen, what zoologists once designated type, has in the doctrine of Descent become the family-in each family lies the potentiality of a certain grade of perfection; and when the main outline of the family character is established, we see a development taking place, of which the potentiality is inherent in the tendency of the character, the realization and necessity in the external conditions. Hence to us also, progress is development, but not towards a predestined and pre-established harmony. Karl Ernst v. Baer, anxious to rescue design, or at least the "purpose”—in short, predestiny, in the evolutionary series of Nature, says: "Every cause engenders a process which again works on towards another purpose." But why
purpose? Ought it not rather to be: Every cause engenders a process which again works on towards. another process? The further we go back, the deeper and more general is the grade, and the various ramifications at their peripheral ends have either halted, or arrived at very different grades.
An objection frequently made against this result of the doctrine of Descent is, that if all are pressing forward towards perfection, how is it that, besides the higher, so many lower members of the family are able to maintain themselves, and how can the lower families hold their own against the higher, in the struggle for existence? In presence of the irrefutable facts of progress, it is enough to point out that the lower forms. could and can continue to exist wherever they could find space as well as the other necessaries of life. While they here underwent only slight modifications, elsewhere the needful selection led to more profound metamorphoses; and on a subsequent geographical displacement, the newly transformed beings, accustomed to other conditions of existence, were again able to share sea and land with the stationary species. For as diversity is restored now by selection, and the demands for nutriment and other necessaries are likewise different, a partial remission in the struggle must take place.
The preservation of a great many inferior organisms is evidently favoured by the circumstance that just because they are simpler, their propagation is more easily effected. Hence although, especially in limited districts, amid violent competition of superior varieties, countless species must suffer extirpation, yet the struggle for existence and perfection do not exclude the existence
of lower forms. But teleology, as it seems to us, still owes an explanation of what has been explained by the theory of selection. The retardation of the lower organisms, notwithstanding the internal pressure and the appointed purpose, is incomprehensible.
But, it is frequently asked, if you will not hear of a "principle of perfectibility" inherent in organisms (Nageli), of the "divine breath as the inward impulse in the evolutionary history of nature" (Braun), of "tendency to perfectibility" implanted by the Creator (R. Owen), even of the "striving towards the purpose (v. Baer), can chance be supposed to have produced these marvellous higher organizations? To this it may be plainly answered, that this chance, to which purblind humanity allots so great a part wherever the personal interference of a superior Being or the universal “creative and productive principle" is not at hand, has no existence in nature, and that our conviction of the truth of the doctrine of derivation is due to its adjustment of the phenomenal series as causes and effects. Let us remember, and fancy ourselves in possession of, the formula of the universe of Laplace, by the aid of which all future evolutions might be computed in advance. With our limited powers, it is true, it is retrospectively alone that certainty can be approached in the calculation and discrimination of the series. In this we must obliterate the word chance, for causality, as we understand it, makes chance entirely superfluous. Any one who transports himself to the commencement of an evolution, who, for instance, fancies himself present at the genesis of the reptiles, may, from his antediluvian. observatory, look upon the development of the reptile