The same science which affirmed spontaneous generation has not balked before this enterprise, and it has pretended to prove the hidden mechanism which, from the egg spontaneously laid, produces the fearful immensity of animate forms! There have been found naturalists, eminent savants in other respects and possessing great authority, like Lamarck and Darwin, who have imagined that they discovered the laws of the transformation of species.
M. Paul Janet, in the book which we cited above, has made a sharp and searching criticism of the theories of Lamarck and Darwin. He asks, in the first place, in what the hypothesis of a plan and of a design of nature, otherwise called the doctrine of final causes, would be contrary to the spirit of science. We must not undertake phenomenal analysis with the premeditated design of finding the phenomena conformable to an object decreed in advance; this preconceived object should never take the place of reason and be the explanation of the facts observed; such a manner of proceeding is hardly scientific, and leads fatally to arbitrary and erroneous conceptions. But does it follow that the facts observed and analyzed in themselves should not, by their collection and connection, express to the human intelligence a superior design, a progressive and ascending harmony, which are its final reason and vivifying spirit? To refuse in advance every final cause is an error similar to that of imagining it altogether and before the observation of the phenomena. Flourens has well said: "We must proceed not from the final causes to the facts, but from the facts to the final causes." These are the fruitful principles, and this is true natural philosophy.
"The naturalists," says M. Janet, "imagine that they have destroyed final causes in nature when they have proved that certain effects result necessarily from certain given causes. The discovery of efficient causes appears to them a decisive argument against the existence of final causes. We must not say, according to them, "that the bird has wings for the purpose of flying, but that it flies because it has wings." But in what, pray, are these two propositions contradictory? Supposing that the bird has wings to fly, must not its flight be the result of the structure of its wings? And from the fact that the flight is a result, we have not the right to conclude that it is not an end. In order, then, that your materialists should recognize an aim and a choice, must there be in nature effects without a cause, or effects disproportioned to their causes? Final causes are not miracles; to obtain a certain end the author of things must choose secondary causes precisely adapted to the intended effect. Consequently, what is there astonishing in the fact that in the study of those causes you should be able to deduce mechanically from them their effects? The contrary would be impossible and absurd. Thus, explain to us as much as you please that, a wing being given, the bird must fly; that does not at all prove that the wings were not given to it for the purpose of flying. In good faith we ask, If the author of nature willed that birds should fly, what could he do better than give them wings for that object?
The demonstration of the reality of final causes, and of a decreed and premeditated plan in nature, furnishes a primary and powerful refutation of the systems which pretend to explain the successive formation of organized beings by the sole action of natural forces, acting fatally, petrifying, modifying, transforming living matter in an unconscious and blind manner. Lamarck and Darwin, as we have said, are the two naturalists who have substituted most successfully a fatal, necessary, and in some sort mechanical plan, instead of a premeditated plan, realized by an intelligent and spontaneous cause. Lamarck appealed especially to the action of means, habit, and want. The combined action of those agents sufficed to him to conclude from the rudimentary cell to man himself.
The action of means, exterior conditions, can modify the form and the functions of living beings; this is a fact of which the domestication of animals offers the most striking examples. But does it follow that because we can modify certain animal and vegetable species, we can therefore create their species? Can we imagine the possibility of modifications so active and powerful that they arrive at the most complex creations, at the construction of the great organs of animal life, and of those organs of the senses, so diverse and so marvellously adapted to their functions? "For instance," says M. Janet, "certain animals breathe through their lungs, and others by the bronchial tubes, and these two kinds of organs are perfectly adapted to the two means of air and water. How can we conceive that these two means should be able to produce so complicated and so suitable organizations? Is there a single fact among all those proved by science which could justify so great an extension of the action of means? If it is said that by means we must not understand merely the element in which the animal lives, but every kind of exterior circumstance, then, I ask, let the materialists determine what is precisely the circumstance which has caused such an organ to take the form of the lung, and such another to take the form of the bronchia; what is the precise cause which has created the heart—that hydraulic machine so powerful and so easy, and whose movements are so industriously combined to receive the blood which comes from all the organs to the heart and send it back through the veins; what is the cause, finally, which binds all these organs together and makes the living being, according to the expression of Cuvier, "a closed system, all of whose parts concur to a common action by a reciprocal reaction?" What will it be if we pass to the organs of sense; to the most marvellous of them, the eye of man or that of the eagle? Is there one of those savants who have no system who would dare to maintain that he sees in any way how light could produce by its action the organ which is appropriated to it? Or, if it is not light, what is the exterior agent sufficiently powerful, sufficiently ingenious, sufficiently skilled in geometry, to construct that marvellous apparatus which has made Newton say: "Can he that made the eye be ignorant of the laws of optics?" Remarkable expression, which, coming from so great a master, should make the forgers of systems of cosmogony reflect an instant, no matter how learnedly they may dilate on the origin of planets, and who pass with so much complacency over the origin of conscience and life!
If the action of means is incapable by itself of explaining the formation of organs and the production of species—what Lamarck calls the power of life, namely, habit and want—how can they give us the sufficient reason for those great facts? According to Lamarck, necessity produces organs, habit develops and fortifies them. But what is this necessity and this habit which are appealed to so complacently, and who proves their strange power? Let us take the necessity of breathing, of which M. Janet wrote as we have quoted. Whence comes this necessity? From the necessity of giving to the blood the oxygen which is necessary for it; and this latter necessity is derived from the necessity of keeping up the organic combustion, and furnishing the nervous system with an appropriate stimulant. Who does not see that there is here a connection of functions and organs which requires a simultaneous creation, which displays a preconceived plan, and not a successive growth of organs according to wants which find in each other the principle of their being, and which cannot be perceived and satisfied separately? What unheard-of aberration, what decadence of the scientific spirit, to transform necessity into a sort of effective and creative power; to make of a sentiment, ordinarily vague and obscure, a new and active entity, which not only animates the created being, but actually creates it!
Lamarck, it is true, admits that observation cannot demonstrate the producing power which he attributes to want; but if a direct proof is wanting, he considers an indirect proof sufficient by appealing to custom. What does he mean? Habit can develop and fortify existing organs by an appropriate and sustained exercise; but how does that prove that want can create them? How can habit develop an organ which does not exist? How can the development of an organ be compared to the creation of this organ, or make us realize the mode of creation of the organ? We can conceive want as the reason not of the creation but of the development of an organ, and habit as excited and sustained by this need; but the need of an organ which is absolutely wanting cannot be born of itself, cannot produce the organ, cannot excite habit. How can an animal deprived of every organ of seeing or hearing experience the want of sight or hearing, or acquire the habit of either? What chimerical hypotheses!
Let us hold to the judgment of Cuvier on all these hypotheses, whose authority is very great:
"Some naturalists, more material in their ideas, and relying on the philosophical observations of which we have just spoken, have remained humble followers of Maillet, (Talliamed,) [Footnote 110] seeing that the greater or less use of a member increases or diminishes its force and volume, have imagined that habits and exterior influences, continued for a long time, could change by degrees the forms of animals so as to make them attain successively all those shapes which the different species of animals now have. No more superficial and foolish idea could be imagined. Organized bodies are considered as a mere mass of paste or clay, which could be moulded by the fingers. Consequently, the moment these authors wish to enter into detail, they fall into absurdities. Whoever dares to advance seriously that a fish by keeping on dry land could change its scales into feathers and become a bird, or that a quadruped by passing through narrow places would become elongated like a thread and transformed into a serpent, only proves his profound ignorance of anatomy."
[Footnote 110: Benoit de Maillet was the predecessor of Lamarck.]