A Philosophical Approach to Evolution
Transformism is an alchemy of nature. That is to point out in a word both what is useful and fruitful about it, and what is transitory and incomplete. Its usefulness, first, consists in this: to suppose, underneath the brute diversity and the apparent independence of beings that coexist or succeed one another, a continuous bond; and in this way to prepare the ground for a new extension of mathematical determinism and to suggest that, even in the most supple organisms, there is still a law of numbers to be found, mensura et pondere (measure and weight). It senses that the living relations that make up the unity of the world have their equivalent in other, abstract relations which deduction will establish in its technical language. Going from the homogeneous to the heterogeneous, cosmic, physical, biological, social actions result from an adaptation to the universal milieu. Thus every fact, like every being, is an expression of the total continuity, solidarity and unity, a product of the common history of all, a particular and passing solution to the general problem of the world. And this problem grows more complex as the successive solutions enrich it with new data through the incessant search for an equilibrium that is always being upset. Great and fruitful is the idea of a sympathetic solidarity among all beings that, as it were, build one another up, just as the members of a perpetually growing organism complement one another; a prophetic hypothesis that symbolizes, but without scientific rigor, the precise formula of the concert composed by the universe; a presentiment of truths that a more advanced science will have to define and limit by completing them.
Indeed, what is lacking in transformism, what makes it fiction rather than a science of nature, is the following. As the alchemist, starting from the transmutations he saw taking place before his eyes, made pretense of finally extracting the gold from all the bodies which he thought he was leading to their perfection, so also the transformist is persuaded he will discover the progression of the rudimentary beginnings of life toward the higher forms and toward humanity. Must not the reproach made against one be applied, by analogy, to the other? In what, then, does alchemy merit the discredit of false science that has been associated with its name? Satisfied ordinarily with resemblances or superficial verisimilitudes, it mixed the most temerarious views in with its positive experiments, without discerning the part played by the imaginary in the perception of the real. Lacking a method able to eliminate the chances of error and to determine the precise object of its inquiries, out of its curiosity it sought a goal external to science itself; and, prescinding from all the irreducible qualities of the bodies that direct experience offered it, it endeavored nevertheless, through a lack of coherence that went unnoticed, to reduce all of them to one and the same quality.
So it is with the transformist: allowing for differences, he seems to be at the point where, not knowing the positive laws of chemical compounding, people still believed in the transmutation of elements. When he appeals to the struggle for survival or natural selection, when amidst the anomalies of heredity he seizes upon certain visible transformations to construct a thesis which he hastens to declare scientific, is that not still to be persuaded that, in science, verisimilitudes and descriptive approximations are enough? Is it not to proceed by half measures, without being careful first to define and delimit the affirmations through the negative method of counter-proof, which alone can eliminate the causes of illusion and impose rigorous conclusions and confer upon them a demonstrative value? If he judges according to the "mere observation of favorable appearances that the living species issued from one another through imperceptible transformations, he is behaving, if not like the alchemist who calls mercury quick-silver, at least like the chemist who would imagine, between carbon monoxide and carbonic acid, a gradation of more or less oxygenated states wherein we could pass from one to the other.
To judge roughly about organic modifications or resemblances, to presume imperceptible transitions, to hope that, by pulling the stages of the universal metamorphosis infinitely close together, we shall cause all difficulty and all discontinuity to vanish, like a housekeeper who disperses a pile of dust to make it invisible to less observant eyes, is therefore to make illegitimate use of mathematical analogies and of the illusions of the imagination in opposition to the method and the originality of the natural sciences. As legitimate and scientific as it is to establish the close dependence of parts that sustain one another, and to have the same elements and the same laws of composition circulating from one end of the world to the other, it is no less temerarious and inconsistent to misrepresent, in the midst of a certain homogeneity, an equally certain heterogeneity.
For even supposing that in the laboratory of nature we were to see a new species come from a determinate species under the influence of complex causes, as unforeseen combinations are formed in a retort where many substances are mixed together, the problem of the transmission and the transformation of the organism would not thereby be resolved. If the alchemist was inconsequential in suppressing all the specific qualities of bodies to look for one final quality, the transformist is equally inconsequential when he prescinds from the derived species, as if it did not have its irreducible quality, in order to concentrate on the original species, on the primitive cell which he considers as a fixed datum. The former did not believe in the specificity of metals, and yet he was looking for a fixed species, gold; the latter does not believe in the specificity of organisms, and he claims to reduce all beings to one type; that is to say, in abstracting from the heterogeneous quality, he misuses homogeneous continuity to definitively set up one initial or final quality, as if there could be one unique type from which the others would come through combination, in the same way as quantities come from numerical unities.
Therefore, we must admit from the start, and beginning with the first germ of life, an infinitesimal coordination of parts, a specific system, a combination of the organized elements that is quite sui generis. Otherwise there would be no biological chemistry, nor any science possible about life, because everything would be amorphous in life. If a definite synthesis changes, it can only form another definite synthesis, just as a distinct individual comes from a distinct individual. Whatever the origin of the living species, the question of their fundamental difference therefore remains intact: there is an essential distinction on which the positive character of the sciences of nature depends. The problem of the real origin and of the constitution of beings is quite different from the problem of the historical descent and the organic composition of living forms; and in order not to do metaphysics without knowing it, we must separate these problems, since science is forever incompetent regarding the first.
Under what condition will phylogeny and ontogeny take on a properly scientific character; and what will remain of transformism when, after ceasing to be a doctrine and to aspire to pronounce the last word and hold the great secret of things, it takes its place in the system of the experimental sciences, which will preserve and surpass the truth of this hypothesis, as of so many others, after having avoided and condemned its excesses?
To the extent that one can look into the future, no doubt this much will remain. We shall know scientifically that, from the last always provisional element that will reach to the most complex syntheses of life, there circulates one and the same sap and the same formula of composition. Already crystallography is studying the architectural plan of the atoms in the molecule. If it succeeds in determining how the elements combine and are composed, how they are juxtaposed in crystallizing according to mechanical laws which mathematics will be able to grasp, organic compounds will themselves be able to be defined rigorously in function of their histological structure; then we shall no doubt know how the connexion of organs and the correlation of forms, whose harmony among higher beings seems to obey more a law of aesthetic finality than a geometric order, depends upon the specific nature of the elementary combinations that are expressed in the whole of the living being; we shall know how the organic synthesis is subject to the precise laws of a crystallization, how even the variety of races according to milieus is a case of polymorphism. Thus the unity of composition in nature and the universal concatenation of facts, forms and beings would no longer be an indeterminate hypothesis or a vague approximation based on verisimilitudes or generalities; it would be a formula that deduction could exploit, and which would verify in rigorous detail the old saying: Homo de limo terrae (man is from the slime of the earth). That is how not only astronomy, but also physics, and chemisty, and now biology, and perhaps soon sociology no longer appear to hinge on a problem of rational mechanics. An obviously fanciful result; but it is useful to suppose science as perfected, in order to see that even then scientific cohesion would not exist.
But how can this real continuity be thus mathematically determined? Will it be on condition that among all the forms of the organization where will be imperceptible gradations and confused indetermination as in a mass of dough ready to be molded little by little all sorts of vague influences? In no way. For, quite on the contrary, the determinism of the mathematical continuity in nature requires that at each stage, as close as we suppose them to be, in each of particular syntheses, as analogous as they may be, there be a precise determination and an intrinsic organization of the original composite. In the experimental sciences, therefore, the use of continuous deduction is subordinated to the discontinuity of the real syntheses; and quantity is appropriate in it only to bring out what is always proper to and irreducible in quality. Once numbers have been introduced into them, the sensible data are maintained by the precision and the rigid fixity of mathematics against mathematics itself.
 We must in effect distinguish between the constitution of the organic elements and the composition or the arrangement of the organs: to effect the synthesis of gallic acid is not to produce a nutgall. Do we appreciate the difficulty of defining the law of this assemblage exactly?
Action. Essay on a Critique of Life and a Science of Practice, transl. by O. Blanchette, University of Notre Dame Press, Notre Dame (IN) 1984, pp. 79-83