A mechanistic theory is one which means to show us the gradual building-up of the machine under the influence of external circ.u.mstances intervening either directly by action on the tissues or indirectly by the selection of better-adapted ones. But, whatever form this theory may take, supposing it avails at all to explain the detail of the parts, it throws no light on their correlation.

Then comes the doctrine of finality, which says that the parts have been brought together on a preconceived plan with a view to a certain end. In this it likens the labor of nature to that of the workman, who also proceeds by the a.s.semblage of parts with a view to the realization of an idea or the imitation of a model. Mechanism, here, reproaches finalism with its anthropomorphic character, and rightly. But it fails to see that itself proceeds according to this method--somewhat mutilated! True, it has got rid of the end pursued or the ideal model. But it also holds that nature has worked like a human being by bringing parts together, while a mere glance at the development of an embryo shows that life goes to work in a very different way. _Life does not proceed by the a.s.sociation and addition of elements, but by dissociation and division._

We must get beyond both points of view, both mechanism and finalism being, at bottom, only standpoints to which the human mind has been led by considering the work of man. But in what direction can we go beyond them? We have said that in a.n.a.lyzing the structure of an organ, we can go on decomposing for ever, although the function of the whole is a simple thing. This contrast between the infinite complexity of the organ and the extreme simplicity of the function is what should open our eyes.

In general, when the same object appears in one aspect and in another as infinitely complex, the two aspects have by no means the same importance, or rather the same degree of reality. In such cases, the simplicity belongs to the object itself, and the infinite complexity to the views we take in turning around it, to the symbols by which our senses or intellect represent it to us, or, more generally, to elements _of a different order_, with which we try to imitate it artificially, but with which it remains incommensurable, being of a different nature.

An artist of genius has painted a figure on his canvas. We can imitate his picture with many-colored squares of mosaic. And we shall reproduce the curves and shades of the model so much the better as our squares are smaller, more numerous and more varied in tone. But an infinity of elements infinitely small, presenting an infinity of shades, would be necessary to obtain the exact equivalent of the figure that the artist has conceived as a simple thing, which he has wished to transport as a whole to the canvas, and which is the more complete the more it strikes us as the projection of an indivisible intuition. Now, suppose our eyes so made that they cannot help seeing in the work of the master a mosaic effect. Or suppose our intellect so made that it cannot explain the appearance of the figure on the canvas except as a work of mosaic. We should then be able to speak simply of a collection of little squares, and we should be under the mechanistic hypothesis. We might add that, beside the materiality of the collection, there must be a plan on which the artist worked; and then we should be expressing ourselves as finalists. But in neither case should we have got at the real process, for there are no squares brought together. It is the picture, _i.e._ the simple act, projected on the canvas, which, by the mere fact of entering into our perception, is _de_composed before our eyes into thousands and thousands of little squares which present, as _re_composed, a wonderful arrangement. So the eye, with its marvelous complexity of structure, may be only the simple act of vision, divided _for us_ into a mosaic of cells, whose order seems marvelous to us because we have conceived the whole as an a.s.semblage.

If I raise my hand from A to B, this movement appears to me under two aspects at once. Felt from within, it is a simple, indivisible act.

Perceived from without, it is the course of a certain curve, AB. In this curve I can distinguish as many positions as I please, and the line itself might be defined as a certain mutual coordination of these positions. But the positions, infinite in number, and the order in which they are connected, have sprung automatically from the indivisible act by which my hand has gone from A to B. Mechanism, here, would consist in seeing only the positions. Finalism would take their order into account. But both mechanism and finalism would leave on one side the movement, which is reality itself. In one sense, the movement is _more_ than the positions and than their order; for it is sufficient to make it in its indivisible simplicity to secure that the infinity of the successive positions as also their order be given at once--with something else which is neither order nor position but which is essential, the mobility. But, in another sense, the movement is _less_ than the series of positions and their connecting order; for, to arrange points in a certain order, it is necessary first to conceive the order and then to realize it with points, there must be the work of a.s.semblage and there must be intelligence, whereas the simple movement of the hand contains nothing of either. It is not intelligent, in the human sense of the word, and it is not an a.s.semblage, for it is not made up of elements. Just so with the relation of the eye to vision. There is in vision _more_ than the component cells of the eye and their mutual coordination: in this sense, neither mechanism nor finalism go far enough. But, in another sense, mechanism and finalism both go too far, for they attribute to Nature the most formidable of the labors of Hercules in holding that she has exalted to the simple act of vision an infinity of infinitely complex elements, whereas Nature has had no more trouble in making an eye than I have in lifting my hand. Nature"s simple act has divided itself automatically into an infinity of elements which are then found to be coordinated to one idea, just as the movement of my hand has dropped an infinity of points which are then found to satisfy one equation.

We find it very hard to see things in that light, because we cannot help conceiving organization as manufacturing. But it is one thing to manufacture, and quite another to organize. Manufacturing is peculiar to man. It consists in a.s.sembling parts of matter which we have cut out in such manner that we can fit them together and obtain from them a common action. The parts are arranged, so to speak, around the action as an ideal centre. To manufacture, therefore, is to work from the periphery to the centre, or, as the philosophers say, from the many to the one.

Organization, on the contrary, works from the centre to the periphery.

It begins in a point that is almost a mathematical point, and spreads around this point by concentric waves which go on enlarging. The work of manufacturing is the more effective, the greater the quant.i.ty of matter dealt with. It proceeds by concentration and compression. The organizing act, on the contrary, has something explosive about it: it needs at the beginning the smallest possible place, a minimum of matter, as if the organizing forces only entered s.p.a.ce reluctantly. The spermatozoon, which sets in motion the evolutionary process of the embryonic life, is one of the smallest cells of the organism; and it is only a small part of the spermatozoon which really takes part in the operation.

But these are only superficial differences. Digging beneath them, we think, a deeper difference would be found.

A manufactured thing delineates exactly the form of the work of manufacturing it. I mean that the manufacturer finds in his product exactly what he has put into it. If he is going to make a machine, he cuts out its pieces one by one and then puts them together: the machine, when made, will show both the pieces and their a.s.semblage. The whole of the result represents the whole of the work; and to each part of the work corresponds a part of the result.

Now I recognize that positive science can and should proceed as if organization was like making a machine. Only so will it have any hold on organized bodies. For its object is not to show us the essence of things, but to furnish us with the best means of acting on them. Physics and chemistry are well advanced sciences, and living matter lends itself to our action only so far as we can treat it by the processes of our physics and chemistry. Organization can therefore only be studied scientifically if the organized body has first been likened to a machine. The cells will be the pieces of the machine, the organism their a.s.semblage, and the elementary labors which have organized the parts will be regarded as the real elements of the labor which has organized the whole. This is the standpoint of science. Quite different, in our opinion, is that of philosophy.

For us, the whole of an organized machine may, strictly speaking, represent the whole of the organizing work (this is, however, only approximately true), yet the parts of the machine do not correspond to parts of the work, because _the materiality of this machine does not represent a sum of means employed, but a sum of obstacles avoided_: it is a negation rather than a positive reality. So, as we have shown in a former study, vision is a power which should attain _by right_ an infinity of things inaccessible to our eyes. But such a vision would not be continued into action; it might suit a phantom, but not a living being. The vision of a living being is an _effective_ vision, limited to objects on which the being can act: it is a vision that is _ca.n.a.lized_, and the visual apparatus simply symbolizes the work of ca.n.a.lizing.

Therefore the creation of the visual apparatus is no more explained by the a.s.sembling of its anatomic elements than the digging of a ca.n.a.l could be explained by the heaping up of the earth which might have formed its banks. A mechanistic theory would maintain that the earth had been brought cart-load by cart-load; finalism would add that it had not been dumped down at random, that the carters had followed a plan.

But both theories would be mistaken, for the ca.n.a.l has been made in another way.

With greater precision, we may compare the process by which nature constructs an eye to the simple act by which we raise the hand. But we supposed at first that the hand met with no resistance. Let us now imagine that, instead of moving in air, the hand has to pa.s.s through iron filings which are compressed and offer resistance to it in proportion as it goes forward. At a certain moment the hand will have exhausted its effort, and, at this very moment, the filings will be ma.s.sed and coordinated in a certain definite form, to wit, that of the hand that is stopped and of a part of the arm. Now, suppose that the hand and arm are invisible. Lookers-on will seek the reason of the arrangement in the filings themselves and in forces within the ma.s.s.

Some will account for the position of each filing by the action exerted upon it by the neighboring filings: these are the mechanists. Others will prefer to think that a plan of the whole has presided over the detail of these elementary actions: they are the finalists. But the truth is that there has been merely one indivisible act, that of the hand pa.s.sing through the filings: the inexhaustible detail of the movement of the grains, as well as the order of their final arrangement, expresses negatively, in a way, this undivided movement, being the unitary form of a resistance, and not a synthesis of positive elementary actions. For this reason, if the arrangement of the grains is termed an "effect" and the movement of the hand a "cause," it may indeed be said that the whole of the effect is explained by the whole of the cause, but to parts of the cause parts of the effect will in no wise correspond.

In other words, neither mechanism nor finalism will here be in place, and we must resort to an explanation of a different kind. Now, in the hypothesis we propose, the relation of vision to the visual apparatus would be very nearly that of the hand to the iron filings that follow, ca.n.a.lize and limit its motion.

The greater the effort of the hand, the farther it will go into the filings. But at whatever point it stops, instantaneously and automatically the filings coordinate and find their equilibrium. So with vision and its organ. According as the undivided act const.i.tuting vision advances more or less, the materiality of the organ is made of a more or less considerable number of mutually coordinated elements, but the order is necessarily complete and perfect. It could not be partial, because, once again, the real process which gives rise to it has no parts. That is what neither mechanism nor finalism takes into account, and it is what we also fail to consider when we wonder at the marvelous structure of an instrument such as the eye. At the bottom of our wondering is always this idea, that it would have been possible for _a part only_ of this coordination to have been realized, that the complete realization is a kind of special favor. This favor the finalists consider as dispensed to them all at once, by the final cause; the mechanists claim to obtain it little by little, by the effect of natural selection; but both see something positive in this coordination, and consequently something fractionable in its cause,--something which admits of every possible degree of achievement. In reality, the cause, though more or less intense, cannot produce its effect except in one piece, and completely finished. According as it goes further and further in the direction of vision, it gives the simple pigmentary ma.s.ses of a lower organism, or the rudimentary eye of a Serpula, or the slightly differentiated eye of the Alciope, or the marvelously perfected eye of the bird; but all these organs, unequal as is their complexity, necessarily present an equal coordination. For this reason, no matter how distant two animal species may be from each other, if the progress toward vision has gone equally far in both, there is the same visual organ in each case, for the form of the organ only expresses the degree in which the exercise of the function has been obtained.

But, in speaking of a progress toward vision, are we not coming back to the old notion of finality? It would be so, undoubtedly, if this progress required the conscious or unconscious idea of an end to be attained. But it is really effected in virtue of the original impetus of life; it is implied in this movement itself, and that is just why it is found in independent lines of evolution. If now we are asked why and how it is implied therein, we reply that life is, more than anything else, a tendency to act on inert matter. The direction of this action is not predetermined; hence the unforeseeable variety of forms which life, in evolving, sows along its path. But this action always presents, to some extent, the character of contingency; it implies at least a rudiment of choice. Now a choice involves the antic.i.p.atory idea of several possible actions. Possibilities of action must therefore be marked out for the living being before the action itself. Visual perception is nothing else:[50] the visible outlines of bodies are the design of our eventual action on them. Vision will be found, therefore, in different degrees in the most diverse animals, and it will appear in the same complexity of structure wherever it has reached the same degree of intensity.

We have dwelt on these resemblances of structure in general, and on the example of the eye in particular, because we had to define our att.i.tude toward mechanism on the one hand and finalism on the other. It remains for us to describe it more precisely in itself. This we shall now do by showing the divergent results of evolution not as presenting a.n.a.logies, but as themselves mutually complementary.

FOOTNOTES:

[Footnote 3: _Matiere et memoire_, Paris, 1896, chaps. ii. and iii.]

[Footnote 4: Calkins, _Studies on the Life History of Protozoa (Archiv f. Entwicklungsmechanik_, vol. xv., 1903, pp. 139-186).]

[Footnote 5: Sedgwick Minot, _On Certain Phenomena of Growing Old_ (_Proc. Amer. a.s.soc. for the Advancement of Science_, 39th Meeting, Salem, 1891, pp. 271-288).]

[Footnote 6: Le Dantec, _L"Individualite et l"erreur individualiste_, Paris, 1905, pp. 84 ff.]

[Footnote 7: Metchnikoff, _La Degenerescence senile_ (_Annee biologique_, iii., 1897, pp. 249 ff.). Cf. by the same author, _La Nature humaine_, Paris, 1903, pp. 312 ff.]

[Footnote 8: Roule, _L"Embryologie generale_, Paris, 1893, p. 319.]

[Footnote 9: The irreversibility of the series of living beings has been well set forth by Baldwin (_Development and Evolution_, New York, 1902; in particular p. 327).]

[Footnote 10: We have dwelt on this point and tried to make it clear in the _Essai sur les donnees immediates de la conscience_, pp. 140-151.]

[Footnote 11: In his fine work on _Genius in Art_ (_Le Genie dans l"art_), M. Seailles develops this twofold thesis, that art is a continuation of nature and that life is creation. We should willingly accept the second formula; but by creation must we understand, as the author does, a _synthesis_ of elements? Where the elements pre-exist, the synthesis that will be made is virtually given, being only one of the possible arrangements. This arrangement a superhuman intellect could have perceived in advance among all the possible ones that surround it.

We hold, on the contrary, that in the domain of life the elements have no real and separate existence. They are manifold mental views of an indivisible process. And for that reason there is radical contingency in progress, incommensurability between what goes before and what follows--in short, duration.]

[Footnote 12: Butschli, _Untersuchungen uber mikroskopische Schaume und das Protoplasma_, Leipzig, 1892, First Part.]

[Footnote 13: Rhumbler, _Versuch einer mechanischen Erklarung der indirekten Zell-und Kernteilung_ (_Roux"s Archiv_, 1896).]

[Footnote 14: Berthold, _Studien uber Protoplasmamechanik_, Leipzig, 1886, p. 102. Cf. the explanation proposed by Le Dantec, _Theorie nouvelle de la vie_, Paris, 1896, p. 60.]

[Footnote 15: Cope, _The Primary Factors of Organic Evolution_, Chicago, 1896, pp. 475-484.]

[Footnote 16: Maupas, "Etude des infusoires cilies" (_Arch. de zoologie experimentale_, 1883, pp. 47, 491, 518, 549, in particular). P. Vignon, _Recherches de cytologie generale sur les epitheliums_, Paris, 1902, p.

655. A profound study of the motions of the Infusoria and a very penetrating criticism of the idea of tropism have been made recently by Jennings (_Contributions to the Study of the Behavior of Lower Organisms_, Washington, 1904). The "type of behavior" of these lower organisms, as Jennings defines it (pp. 237-252), is unquestionably of the psychological order.]

[Footnote 17: E.B. Wilson, _The Cell in Development and Inheritance_, New York, 1897, p. 330.]

[Footnote 18: Dastre, _La Vie et la mort_, p. 43.]

[Footnote 19: Laplace, _Introduction a la theorie a.n.a.lytique des probabilites_ (_OEuvres completes_, vol. vii., Paris, 1886, p. vi.).]

[Footnote 20: Du Bois-Reymond, _uber die Grenzen des Naturerkennens_, Leipzig, 1892.]

[Footnote 21: There are really two lines to follow in contemporary neo-vitalism: on the one hand, the a.s.sertion that pure mechanism is insufficient, which a.s.sumes great authority when made by such scientists as Driesch or Reinke, for example; and, on the other hand, the hypotheses which this vitalism superposes on mechanism (the "entelechies" of Driesch, and the "dominants" of Reinke, etc.). Of these two parts, the former is perhaps the more interesting. See the admirable studies of Driesch--_Die Lokalisation morphogenetischer Vorgange_, Leipzig, 1899; _Die organischen Regulationen_, Leipzig, 1901; _Naturbegriffe und Natururteile_, Leipzig, 1904; _Der Vitalismus als Geschichte und als Lehre_, Leipzig, 1905; and of Reinke--_Die Welt als Tat_, Berlin, 1899; _Einleitung in die theoretische Biologie_, Berlin, 1901; _Philosophie der Botanik_, Leipzig, 1905.]

[Footnote 22: P. Guerin, _Les Connaissances actuelles sur la fecondation chez les phanerogames_, Paris, 1904, pp. 144-148. Cf. Delage, _L"Heredite_, 2nd edition, 1903, pp. 140 ff.]

[Footnote 23: Mobius, _Beitrage zur Lehre von der Fortpflanzung der Gewachse_, Jena, 1897, pp. 203-206 in particular. Cf. Hartog, "Sur les phenomenes de reproduction" (_Annee biologique_, 1895, pp. 707-709).]

[Footnote 24: Paul Janet, _Les Causes finales_, Paris, 1876, p. 83.]

[Footnote 25: _Ibid._ p. 80.]

[Footnote 26: Darwin, _Origin of Species_, chap. ii.]

[Footnote 27: Bateson, _Materials for the Study of Variation_, London, 1894, especially pp. 567 ff. Cf. Scott, "Variations and Mutations"

(_American Journal of Science_, Nov. 1894).]

[Footnote 28: De Vries, _Die Mutationstheorie_, Leipzig, 1901-1903. Cf., by the same author, _Species and Varieties_, Chicago, 1905.]

[Footnote 29: Darwin, _Origin of Species_, chap. vi.]

[Footnote 30: Darwin, _Origin of Species_, chap. i.]

[Footnote 31: On this h.o.m.ology of hair and teeth, see Brandt, "uber ...

eine mutma.s.sliche h.o.m.ologie der Haare und Zahne" (_Biol. Centralblatt_, vol. xviii., 1898, especially pp. 262 ff.).]