HOW CAME A PERFECT EYE?

25

attempt to reduce the doctrine of what used to be called Chance to an orderly philosophic system. Mr. Darwin accounts for the structure of the Eye not by Chance but by Natural Selection.

"To suppose," he says, "that the eye, with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree. Yet reason tells me, that if numerous gradations from a perfect and complex eye to one very imperfect and simple, each grade being useful to its possessor, can be shewn to exist; if, further, the eye does vary ever so slightly, and the variations be inherited, which is certainly the case; and if any variation or modification in the organ be ever useful to an animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, can hardly be considered real"."

o Darwin, Origin of Species, p. 186.

This passage makes it plain that M. Comte cannot count Mr. Darwin among his followers, since the latter philosopher in no way derogates from the splendour of the instrument, but only attempts to account for the mode of its construction. M. Comte, on the other hand, seems not only to follow Lucretius in attributing the Eye to Chance, but holds, as one might expect, that the result is bad, bad in two ways:

1st. In that the crystalline lens is not indispensable for the purpose of vision.

2nd. In that, though not necessary for vision, it becomes in certain cases capable of impeding it altogether.

Nor is this all. For a conclusion follows which must not be unnoticed-that the course of nature as it is, is inferior to what it might have been if under the control of human intelligence.

"Quoique notre imagination reste nécessairement circonscrite, en tous genres, dans la seule sphère de nos observations effectives, et que, par suite, il nous soit surtout impossible d'imaginer des organismes radicalement nouveaux, on ne saurait douter,

IS THE LENS USELESS AND HURTFUL? 27

néanmoins, ce me semble, que le génie scientifique ne soit aujourd'hui, même en biologie, assez développé et assez émancipé pour que nous puissions directement concevoir, d'après l'ensemble de nos lois biologiques, des organisations qui diffèrent notablement de toutes celles que nous connaissons, et qui leur seraient incontestablement supérieures sous tel point de vue déterminé P, sans que ces améliorations fussent inévitablement compensées, à d'autres égards, par des imperfections équivalentes 9.

["Although our imagination remains necessarily circumscribed in all respects within the sphere of actual observation, and, in consequence, it is impossible for us to imagine organisms radically new, we cannot doubt, as appears to me, that the genius of science is now sufficiently developed and sufficiently free for us to be able directly to conceive, in conformity with the aggregate of our biological laws, organisms which differ notably from all that we know, and which would be incontestably superior to them under a definite point of view, while

p Compare the more modest opinion of the great practical Naturalist just quoted, below at p. 40.

a Comte, Cours de Philosophie Positive, vol. iii. p. 322.

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THE NORMAL EYE.

these ameliorations might not be inevitably balanced, in other respects, by equivalent imperfections."]

In weighing arguments of this kind, we must not be slow to admit, first, that our faculties are so far limited that we are not able to discover with certainty all the conditions necessary for producing a structure so complicated as the Eye; and secondly, that such structure, when made, is still within the range of action of the more general laws which regulate matter on the earth.

For, of the cause of the origin of any given structure, as the Eye, no more is known than of that of any other organic structure. The whole process is not within the range of the human mind to comprehend. We can only predicate of it, with Comte, the phænomena which we are able to investigate.

An Eye, considered philosophically, is the connecting machinery between light and a recipient consciousness.

As an instrument, it fails in its purposer,

r No excuse is made for the assumption, in this part of the argument, of purpose and adaptation. To avoid it

1

THE LAWS OF ACTION.

29

if it be not adapted to the laws of light on the one hand, and to the psychological capacities of the animal on the other.

When objection is taken to it, it has to be shewn,

either, that it does not transmit light in a suitable manner;

or, that while it transmits light correctly, the mode of transmitting the impression to the consciousness is faulty;—

or, that being constructed reasonably in these particulars, it is liable to derangement beyond that which belongs proportionably to it as a delicate organic structure in a world where existence implies change;

or, that being delicate, and reasonably maintained in existence, it is liable to an extraordinary amount of risk from accidents which might have been guarded against.

Now, it may be answered categorically to each and all of these,

would require an amount of periphrasis which were intolerable. Moreover, it is necessary in a brief summary to speak of the Eye as a whole, as though there were one kind of eye, whereas there are many kinds, acting in different ways, and imparting knowledge different in amount and in quality.