Some Eighteenth Century Evolutionist I
Arthur O. Lovejoy
A SATISFACTORY history of the theory of descent is a chapter in the records of human opinion that is still to be written. Meanwhile the subject is one about which persistent errors and illusions of historical perspective prevail. The popular mind appears to be firmly possessed by the belief that the doctrine of the evolution of species was a scientific innovation first promulgated, or at all events first cogently defended, by Darwin; the fame of the natural-selection hypothesis has become so great that its author figures, in the eyes of the great public, as the parent of the whole transformist system, while the earlier half century of controversy in behalf of that doctrine, under the leadership of Lamarck and of Geoffroy St. Hilaire, is forgotten. How far even instructed persons may suffer from this illusion of perspective was illustrated in the recent commemorations of the Emerson centenary. More than one of the eulogists of the great moralist of New England descanted upon his very un-Darwinian lines which tell how—
striving to be man, the worm
Mounts through all the spires of form,
as a remarkable ‘anticipation of Darwin' and an example of the power of the poetic imagination to divine scientific troth. But the lines in question, added to the editions of Emerson's `Nature' after 1849, are, of course, merely an epigrammatic versification of the main doctrine of Robert Chambers's `Vestiges of Creation,' published in 1844; and the conception they express could hardly have been a very original one at any time after the appearance of Lamarck's ' Philosophie Zoologique' in 1809. The same confusion is illustrated again in the persistency with which writers on Tennyson take it for granted that the famous passage in `In Memoriam' about nature,
so careful of the type,
So careless of the single life,
is an echo of the `Origin of Species,' which in reality did not appear until at least fifteen years after this part of the poem was written. Even Mr. Frederic Harrison has-as Mr. Lang has pointed out-fallen into this error; and Mr. G. K. Chesterton has recently written about Tennyson in a way calculated to give the error fresh currency. But
( 239) even those who do not forget that the theory of the transmutation of species has been a familiar and influential doctrine, established upon fairly conclusive arguments ever since the beginning of the nineteenth century, are likely to forget the fact that the doctrine, in its proper modern form, takes its origin, as a respectably fathered and militant hypothesis, in France in the middle of the eighteenth century. The histories of the theory of evolution mention, indeed, a number of names in the eighteenth and in many earlier centuries,, with which vague and more or less eccentric foreshadowings of the now accepted doctrine are connected. But the books on the subject which we have in English are unfortunately either inadequate or inaccurate or both; and they rather disguise than reveal the real character and significance of the evolutionist movement in the eighteenth century. Many of them-Mr. Clodd's book, for example, and Huxley's essay, and Professor Packard's ' Lamarck,' as well as the French works of Perrier and of Quatrefages on the precursors of Darwin-ignore some of the most important and most influential eighteenth century evolutionists; Professor Osborn's survey ('From the Greeks to Darwin,' 1894) is more comprehensive but regrettably inaccurate. There is therefore some occasion for a fresh attempt to clear up some points in the earlier history of the central conception of modern biology.
It is unfortunate that the eighteenth century manifestations of evolutionism should have so generally been grouped, by those who have written of them, in one class with the ancient adumbrations of Darwinism, as if all alike were merely interesting historic accidents. The ancient foreshadowings of the doctrine were, indeed, little more than happy but fortuitous guesses of ingenious minds. But the mid-eighteenth century outcropping of the theory was a natural, one may almost say an inevitable, consequence of the progress which had up to that time been made in natural science. And the theory found expression, not in the sporadic utterances of an obscure philosopher here and there, but in the best-known writings of three of the most celebrated headers of the opinion of their time; so that, however little it may have gained acceptance, the theory must have been pretty widely known among their contemporaries. It is, of course, a fact sufficiently familiar that Buffon in 1749 propounded the conception of the transformation of species as a possible hypothesis; that he pointed out the homological evidence in favor of such an hypothesis, and tended in some passages to accept it; but that, in his most important passage on
(240) the subject, he rejected it, partly on grounds of religious orthodoxy. Professor Packard, in his life of Lamarck, has recently presented an interesting study of Buffon's exact position in the matter. These equivocal expressions of Buffon's are, however, commonly spoken of as if they were unique in their period; whereas the same hypothesis was put forward, within a decade, by two countrymen of his who were hardly less representative than lie of the scientific progress of their generation. For one of them was the president of the Royal Academy of Science of Berlin; and the other was the editor of, the Encyclopedia.
There were two distinct lines of development in scientific investigation and theory during the first half of the eighteenth century which led up to and suggested the theory of transformation as a natural and probable hypothesis in zoology. The first of these was the active prosecution of both observation and speculation in the field of embryology; the second was the development of the new science of comparative anatomy at the hands of Daubenton. The representative of the former way of approach to evolutionism is Maupertuis. In speaking of him, I venture to improve the occasion to give some general account of his place in the history of science, since the matter is one about which little trustworthy information appears to be generally accessible. Such an account will make the significance and the grounds of his evolutionary opinions more apparent.
I. Maupertuis.—Although not without some reputation as the reorganizer of the Berlin Academy for which task he was especially imported from France by Frederick the Great—and as the director of the first expedition to demonstrate the flattening of the globe at the poles by the measurement of a degree of longitude at different latitudes, Maupertuis is usually made to play a somewhat comic rôle in the literary history of his century, as the rival of Voltaire for the favor of Frederick and as the victim of one of Voltaire's most ferocious satires. Although Frederick took the, side of Maupertuis in that famous quarrel and caused the copies of Voltaire's libel. to be burned by the hangman in all the public places of Berlin, the satirist has been more successful in gaining the ear of posterity. Immensely famous and respected as a sort of scientific oracle in his own day, Maupertuis seems now to be best known through the misrepresentations of his adversary; there is even reason to fear, from internal evidence, that some learned historians of philosophy, in the little they have to say about the `Native of St. Malo'—as Voltaire always designated him—have depended more upon the 'Histoire du Docteur Akakia' than upon a careful examination of Maupertuis's own writings. Yet-in spite of the touch of vanity which sometimes made him ridiculous and the superficiality of a good. deal of his knowledge—his reputation deserves in some measure
(241) to be rehabilitated. He was by no means a great scientific investigator ; his work in physics and in astronomy, which he professed for his chief specialties, seems to be of decidedly questionable accuracy and value. His celebrated `law of least action,' which was the original occasion of his quarrel with Koenig and Voltaire, was a generalization vaguely conceived and ill formulated, although, as Mach has pointed out, it was taken up by Enter, the friend and partisan of Maupertuis, and transformed into an important physical principle. But in any history of the general movement of scientific thought in his century Maupertuis clearly merits a place of some distinction. For he was the possessor of a wide view of the interrelation of different scientific problems; he was an ingenious and yet often a pretty shrewd and critical interpreter of the bearing and ulterior consequences of the scientific discoveries of others;, and he contributed to more than one branch of science new and important conceptions, which during the subsequent century and a half have come into great vogue and in some cases into general acceptance.
As was the fashion of his time, Maupertuis took philosophy as well as physical science for his province; and before considering his work in the latter domain, it is worth noting that in the former also he was the proposer of several notions, now familiar enough, which were at the time relatively novel and contrary to the prevailing intellectual fashions. As a moralist, for example, Maupertuis raised a question that has been repeated with much doleful iteration by his nineteenth century successors, but one highly paradoxical to his contemporaries: In ordinary human life, does the sum of dissatisfactions exceed the sum of pleasures? This question he answered in a pessimistic sense, in an age when a superficial optimism was the proper note among enlightened philosophes—and was reproached for it by the writer who, a few years later, was to produce, the `Poem on the Lisbon Disaster' and 'Candide.' In laying down the logical conditions for dealing with such a question, Maupertuis anticipated Bentham and the `moral arithmetic' of the Utilitarians, by elaborating a species of hedonic calculus, in which careful definitions are offered, not only of the nature of pleasure and pain, but also of the several dimensions of each that must be reckoned in assessing the relative value of any two `sums of pleasure,' or of its contrary. As a political theorist, also, he shows himself a precursor of the English Utilitarian school, at a time when nearly all the new systems of political philosophy were based upon some form of the conception of `natural rights' or `natural law.' In his ' Eloge de M. de Montesquieu' he criticizes the political doctrine of the `Esprit des Lois,' which rests, he says, upon the assumption that there inheres in human relations ' un certain rapport d'équité' which man's reason immediately recognizes. "It is not," writes Maupertuis,
(242) "such a principle as this that should be accepted as the fundamental principle of legislation; this is too obscure, too vague, too susceptible of _different interpretations; it would leave too much to the arbitrary judgment of the legislation." The only safe guide in legislation is the principe du plus grand bonheur. "The problem of the legislator is simply this: A multitude of men being collected together, to procure for them the greatest sum of happiness possible. It is upon his principle that all systems of legislation should be based." All this reads like so many sentences from Bentham himself; and the resemblance is by no means merely coincidental. In the ethical and political writings of Maupertuis and of Helvétius we have the head-waters of the important stream of utilitarian influence which became so broad and sweeping a current through the work of the Benthamites. Bentham read Maupertuis early—perhaps about 1770, in his twenty-second or twenty-third year, thinks a recent writer on the subject  —and although he had already got the suggestion of his doctrine from Priestley and Helvétius and Beccaria, he found, as lie himself tells us, his utilitarian tendencies strengthened and corroborated by his reading of the ' Essai de Philosophic Morale.' The utilitarian political teaching of Maupertuis was enunciated at least three years before the publication of a similar doctrine in the book of Helvétius (De l'Esprit, 1758) ; and that book, Mr. John Morley has said, `contained the one principle capable of supplying such a system of thinking about society as would have taught the French of that time in what direction to look for reforms.' The work of Beccaria, the third of the early influences upon the mind of Bentham, was still later in date of publication (1764).
In treating of the relation of scientific method to theology, Maupertuis—although professing a somewhat perfunctory religious orthodoxy-criticized the favorite eighteenth century argument for theism —the so-called argument from design—in which the deists no less than the orthodox of the period found the principal basis of their religious philosophy; and his criticism upon it is just such as a Darwinian might now make. It closely resembles, indeed, the criticism of the same argument that Romanes put forward long afterward as a special outcome of Darwinism. Many, says Maupertuis, have found an evidence of design in the marvelous adaptation of the organs of animals to their needs. But "may we not say that, in the fortuitous combination of the productions of Nature, since only those creatures could survive in whose organization a certain degree of adaptation was present (ou se trouvaient certains rapports de convenance), there is nothing extraordinary in the fact that such adaptation is actually
( 243) found in all those species which now exist? Chance, one might say, turned out a vast number of individuals; a small proportion of these were organized in such a manner that the animals' organs could satisfy their needs. A much greater number showed neither adaptation nor order; these last have all perished. . . . Thus the species which we see to-day are but a small part of all those that a blind destiny has produced. " Maupertuis did not dogmatically maintain the - antiteleological position which this criticism tended to justify; he only maintained that zoology can not assist theology, because the former has no need of teleological explanations and can sufficiently account for the degree of adaptation which exists on the principle which we should now call that of the survival of the fittest, i. e., of the best adapted.
Maupertuis had also his own theories in metaphysics; but these are so closely connected with his evolutionary views that the two should be considered together. I turn, then, to mention his work in promoting new ideas in natural science. He was the first to introduce the Newtonian physics and astronomy into France. In the face of a good deal of opposition, he successfully disseminated the doctrine of attraction among the learned; and it was apparently from him that Voltaire acquired a sufficient smattering of physics and astronomy to enable him to write his `Eléments de la Philosophie de Newton' (1738). As became the president of an academy, Maupertuis undertook, in his 'Lettres' and 'Lettres sur le Progres des Sciences' to sum up certain of the most important gains that had been made by scientific inquiry, and to lay down a program of experimental investigations next to be undertaken. These investigations, he urged, should be supported by the state, when they are too elaborate or too expensive to be undertaken by private enterprise. Some of his suggestions are pretty fantastic and impracticable; but the greater number show good sense and a keen appreciation of the importance of systematic experimentation, even in sciences where experimental methods had as yet been little used. He recommends, among other things, the exploration of the north and south polar regions, and of the interior of Africa, for the settlement of the chief unsettled questions in geography; urges the employment of experimental methods in zoology, especially in the study of the problems of heredity; advises specialization in medical
(244) practise; proposes the utilization of the bodies of condemned criminals for experiments on the etiology of disease; calls for the prosecution of systematic experiments with electricity, and the abandonment of premature efforts to make practical use of that force, before its properties and behavior had been adequately investigated; and indicates the possibility of the prosecution of certain expériences métaphysiques—i. e., of investigations in what we should now call experimental psychology. He concludes his program somewhat humorously with an enumeration of récherches à imterdire—namely, those `chimeras of science,' the philosopher's stone, the quadrature of the circle and perpetual motion. In regard to the first of these, however—the transmutation of elements-he points out that the thing can not be shown to be inherently impossible. For there are several legitimate hypotheses about the constitution of matter which are compatible with the possibility of transmutation. It is not unlikely, for example, that `matter is composed of homogeneous parts,' and that the elements which appear to possess irreducible qualitative differences, `really differ from one another only by the dissimilar form and arrangement of the homogeneous particles which compose them.' In that case, we should not be entitled to declare it impossible to give `to such particles a different form and arrangement, which is all that would be necessary in order to transmute lead or wool into gold.' The objection to the search for the means of transmuting elements is, therefore, not that it can be demonstrated to aim at the impossible, but only that in the existing state of science, the value of the goal—great as it would be-'is not great enough to counterbalance the scant probability of attaining it.' When one reminds oneself of the hypotheses about the constitution of matter that have come into especial vogue since the discovery of the properties of radium, these observations strike one as the expression of a rather well balanced judgment.
It was, however, in his conception of the methods and the possibilities of natural history that Maupertuis most evidently showed himself the possessor of a wider intellectual horizon than was common among the men of science of his time. Zoologists had as yet seen little occasion to attempt more than the careful description and classification of animals; but to Maupertuis a purely descriptive and classificatory science, which was unable to formulate any laws concerning the processes going on in that part of nature with which it dealt, was, strictly speaking, no science at all. He had little patience with naturalists whose view of their province was so narrow. `All these treatises on animals which we as yet have,' he writes in the 'Lettres sur le Progrès des Sciences,' `are —even the most methodical of them-no better than pictures pretty to look at; in order to make of natural history a veritable science, naturalists must apply themselves to researches which can make us acquainted, not simply with the form of this or that animal, but with the general
(245) processes of nature in the production of animals and the conservation of them.' The general processes which Maupertuis thought it especially important that zoological science should investigate are those through which animal individuals and species have come to have the differences of form and function that distinguish them. Maupertuis, in a word, appears to have clearly envisaged the genetic problem in biology, at a period in the history of thought when genetic problems generally were little considered. The center of interest in zoology therefore lay, for him, in the problems of embryogeny and of heredity. Although not himself an anatomist, he made himself familiar with investigations made by others on the minute anatomy of the embryo. And, as I have intimated, he never tired of insisting that the facts of heredity should be investigated, in the case of animals, by experiments in the interbreeding of species and varieties, and, in the case of human beings, by a collation of family histories.
The opinions of Maupertuis on these matters are expressed chiefly in the work called ` Vénus Physique' (1745) and in the ` Système de la Nature' (1751). The latter first appeared in the form of a Latin dissertation ostensibly delivered at Erlangen by one Dr. Baumann. Maupertuis found it expedient thus to shelter himself against reproach on account of any heterodox tendencies that the book might be found to contain. Four editions-all but the first in French—were called for within four years, and the author soon assumed responsibility for his work. In the `Vénus Physique' Maupertuis essayed the popular style, and the book is consequently marred by passages written in an abominably rhetorical and affected manner. But, none the less, it constitutes, if I am not mistaken, the first important attack made in the eighteenth century upon the theory of the preformation of the embryo. Harvey had advanced the doctrine of epigenesis nearly a century earlier, but his arguments had failed to convince his successors, and his observations upon the chick had been shown by Malpighi to be partially erroneous. At the time when Maupertuis wrote, preformationism had long been the ruling doctrine in embryology; an immense weight of scientific authority was in its favor. Among the philosophers Malebranche and Leibniz had argued for it, among the great physiologists and anatomists Swammerdam, Redi, Malpighi, Leeuwenhoek, Winslow and Haller had taught it. Bonnet was yet to give it its most elaborate exposition and defense; and three quarters of a century later it was still to find an adherent in Cuvier. The ' Vénus Physique' is a review of the preformation theory in its several forms, designed to show that the evidence against it is conclusive.
Of the arguments for epigenesis which Maupertuis offers it is not possible, in this brief paper, to give any sufficient account. He relies in part upon the observations of Harvey—and in so doing shows himself
( 246) not quite abreast of the anatomical knowledge of his time, since, correct as Harvey's main conclusions were, the observations upon which he based them had already been superseded. Chiefly, however, Maupertuis rests his case upon the facts of double heredity and hybridism. If the embryo be truly ' predelineated' in the ovum or in the 'zoosperm,' how, he asks, can it come about that it inherits the specific or individual characters of now one and now the other parent, and often of both? The preformationists had, of course, their devices for explaining away this pretty obvious difficulty; but Maupertuis finds it easy to show that the explanations are altogether inadequate when they are compared with even the common and easily observable facts of heredity. His reasoning is especially effective when he cites his own investigation of the transmission of hexadactylism (sexdigitisme) through several generations of a certain German family whose records he had examined, and points out how little the preformation hypothesis could account for the transmission of such a peculiarity through male and female parents alike, its progressive disappearance as succeeding generations more and more intermarried with persons having the normal number of digits, and its occasional atavistic reappearance in remote descendants. In view of these classes of facts, he declares, the encasement theory must be abandoned, and the conclusion must be accepted that the embryo is no ready-made article, preexistent from the creation of the world, but a new birth, the product of a true genesis; not, indeed, a genesis of life itself, but of a new and unique combination and intermingling of already-living elements contributed by both parents alike. These arguments and this conclusion, it should be remembered, were advanced by Maupertuis more than a decade before the publication of the great work of Kaspar Friedrich Wolff, from which the modern revival of the doctrine of epigenesis is usually dated. The conception of epigenesis held by Maupertuis, was, moreover, far more complete and. accurate than that which Harvey had put forward a century earlier. For although Harvey had asserted marem et foeminam pariter efficientes causas esse generation is, he had denied that there can be any physical interpenetration of ovum and spermatozoon, and had declared that fecundation consists in the communication of a purely immaterial force. It was in order to make this a little more intelligible that Harvey had worked out his famous analogy between the conception of the embryo in the uterus, and the conception of an idea in the brain. All this, Maupertuis remarks, is an idée étrange; where we have double
(247) heredity we must assume a communication of corporeal elements, vehicles of that heredity, from both sides. And, as Maupertuis also observed, the supposed fact by which Harvey had justified this singular conclusion had already been rendered more than questionable by later investigations of Verheyen.
Having established these essential principles to his satisfaction, Maupertuis proceeded to formulate an hypothesis concerning the nature of the fundamental physical process presupposed by the facts of heredity, on the one hand, and of variation, on the other. The formation of an embryo must, he conceived, be due to the combination in a new organic union, of a great number of living corporeal particles, derived usually from both parents, each of which particles carries with it a sort of organic memory (souvenir) of the life of the organism, to which it formerly belonged, and thereby tends to unite with the other particles in such a way as to produce a new organism of the same species. This process of recombination of already living particles was held by Maupertuis to be governed by something more than the laws of mechanism; embryogeny was for him no mere process of juxtaposition, under the laws of gravitation, of so many inert atoms; the ultimate units of the newly constituted living being all possess their own selfcontained law of development, and their own distinctive selective affinities for certain other units. None the less, purely mechanical displacements of parts also take place; and to these in part, he supposed, is due the occurrence of monstrous forms, and many of the more ordinary variations from the hereditary specific type. Moreover, the elementary units which, coming from the parents, combine to form the embryonic offspring, in part carry with them a similar sort of organic memory of the particular and individual characters of the parent, and so tend to develop those characters in that offspring; but in part also they are free from this tendency, and carry with them rather the traits of more remote ancestors (atavism), and some of then may even be wholly independent of hereditary predetermination. It is these especially which, in Maupertuis 's hypothesis  constitute the explanation of the general tendency to variation in animals, which he recognized to the full. If one must have a further explanation why the transmitted corpuscles tend to reproduce the characters of the parents, Maupertuis suggests that perhaps there enters into the embryo a separate germ from each part of the body of the parent of which the character is reproduced; in other words, he proposes a hypothesis similar to the Dar-
( 248) -winian theory of Pangenesis. All these ideas are put forward by Maupertuis only as so many likely explanations of facts which, as he insisted, needed more adequate analysis and explanation than the embryological doctrines of the time afforded; his pangenetic theory, in particular, he regarded only as une conjecture bien hardie, mais qui ne serait peut-être pas destituée de toute vraisemblance.
What is noteworthy in these hypotheses is the group of truths which - they involve incidentally. From Maupertuis 's exposition of them it is clear that he had been led, by his reflections upon the facts of heredity, to recognize (a) that there is a constant tendency to variation in animals by reason of their double heredity; (b) that there is a further tendency to spontaneous and accidental variations, due in part to mechanical displacements or chance combinations among the ultimate particles of which the embryo is composed; (c) that these variations —and possibly also new characters acquired during the lifetime of the parent  —-tend to be perpetuated through heredity, provided that they do not unfit the animals that possess them for survival in their environment, and provided also that they are not gradually obliterated through inter-breeding with animals that do not possess them. To one who thus emphasized the factors making for variation and for the conservation of variations, the theory of the mutability of speciés necessarily appeared more natural than the theory of their fixity. Maupertuis thus passes at once from his theories of heredity to propound the hypothesis that all species may have come from a single primitive pair through the gradual accumulation and transmission of divergent variations. Granting these facts about variation, he writes, "would it not be possible to explain by means of them how the multiplication of the most dissimilar species might be traced back to (aurait pu s'ensuivre de) only two individuals. Such species would have owed their origination merely to the accidental production of certain embryos (c quelques productions fortuites) in which the elementary parts had not retained the arrangement which they had had in the parent animals. Each degree of deviation (erreur) would bring about a new species; and by means of repeated departures from the original form (à force d'écarts repétés) there would have come about the infinite diversity of animals that we see to-day:-a diversity which may in time increase still further, but to which it may be that the lapse of centuries will bring only imperceptible additions" (` Système de la Nature,' SLV.). In the 'Lettres' Maupertuis again writes, à propos of the inheritance of certain congenital individual variations in the human
(249) species: "I hold that these supernumerary digits are, at their first appearance, nothing but accidental variations. . . . But these variations once well established (confirmées) through a sufficient number of generations in which both sexes have had them, constitute (f ondent) species; and it is perhaps thus that all species have multiplied." In fact, for Maupertuis the difficulty lay in explaining, not how species are transformed, but why they are so stable.
It will be seen that Maupertuis puts forward his theory, of transformation only as a likely hypothesis, not as a settled truth. But it is an hypothesis for which he clearly enough indicates his own preference; and it is certain, from a passage of Diderot's which I shall presently quote, that his contemporaries looked upon him as the typical representative of the doctrine of the descent of all species from a primitive type. Yet the significance and originality of the work of Maupertuis lie not so much in his explicit enunciation of the theory of descent, as in the fact that he (1) insistently called the attention of naturalists to the problems connected with the genesis and transmission of variations; (2) framed a conception of the processes involved in embryogeny and heredity which made the mutability of species seem antecedently the more natural and more probable hypothesis ; (3) indicated a program for systematic observation and experimentation with reference to heredity and to the effects of interbreeding, which, if carried out, would have transformed zoology ; (4) intimated that Nature produces a far greater number of types and of individuals than she can maintain, and that among all these variant types there is constantly taking place a process of natural selection whereby those unfitted to the conditions of their life are exterminated; (5) explained the adaptation of animals to their environment solely as the result of these conjoint processes of variation and selection.
It remains to point out that the embryological doctrines of Maupertuis were intimately connected with certain metaphysical conceptions, of a type that has often since shown itself to be peculiarly congenial to minds trained in, biology. The ' Système de la Nature' is primarily an exposition and a defense of the theory that all matter possesses some sort of consciousness—a `monism' similar to that of which Haeckel is the contemporary prophet. A purely mechanistic materialism, such as the atomism of the Epicureans, or the crude notions which La Mettrie had recently put forward, seemed to Maupertuis an evident absurdity; `in order to overthrow such a system,' lie writes, `one need do no more than ask those who hold it how it would be possible for atoms without intelligence to produce an intelligence.' Mere mechanism appeared as little capable of explaining the phenomena of organic life, as it was of explaining the phenomena of consciousness; especially manifest, Maupertuis thought, is the inadequacy of purely mechanical causes to account for the processes which he conceived to be involved in the formation of the embryo. "A blind attraction uniformly distributed throughout all particles of matter can not serve to explain how these particles arrange themselves to form even the simplest of organized bodies. If they all have the same tendency, the same power, to unite with one another, why is it that certain elements go to form the eye, certain others to form the ear, etc. ? Why this marvelous arrangement? Why is it that the various elements are not united pell-mell?" The combination of material particles to form a living organism seemed to imply a principle of selection, a species of elective affinity between the particles, which could not be reduced to physical or chemical categories; and the singular fact of heredity, the transmission of qualitative similarities from one organism to another through whatever minute bodies serve as the vehicles of heredity, seemed to imply the possession by those bodies of something which could only be conceived under the analogy of conscious memory. It is necessary, then, to attribute to each particle of matter the possession of some rudimentary forms of sentiency, memory and volition. (Si l'on veut dire sur cela quelque chose qu'on conçoive, quoiqu'encore on ne le conçoive quo sur quelque analogie, it faut avoir recours a quelque principe d'intelligence, a quelque chose de semblable a ce quo nous appelions désir, aversion, mémoire). Maupertuis does not forget the radical difficulty which has been urged. against the identification of the res cagitans and the res extensa ever since Descartes—the difficulty, namely, that the attributes of consciousness and extension have nothing in common, and that neither can thought be conceived as ex-
(251) -tended, nor extended matter as possessing the unity characteristic of conscious thought. Maupertuis certainly can not be said to meet this difficulty; but he evades it by a device which has been much employed since his time by metaphysicians of opinions kindred to his. The objection in question, he avows, would be a legitimate one against any doctrine that actually asserted the identity of matter and consciousness, reducing matter to thought, or thought to a form or function of matter. But if we say that thought and extension are not things, but properties-distinct but joint properties of a common subject-the difficulty, he contends, disappears. This tertium quid, of which thought and extension are to be defined as coexisting properties, is something `of which the essence is unknown to us' ('Syst. de la Nat.,' 22). Maupertuis at this point appears, on the one hand, as repeating the dialectical strategy of Spinoza, a philosopher almost wholly ignored in the eighteenth century; and, on the other hand, as a precursor of Mr. Herbert Spencer, with his conception of the `double aspect of an ultimately unknowable substance.' Maupertuis, however, was not a psychophysical parallelist; on the contrary, as I have pointed out, the sentiency which he attributed to matter was regarded by him as an essential factor in the explanation of physical events.
How Maupertuis would have reconciled the apparent—even though `transfigured'—realism of this doctrine of conscious matter with the idealistic view of the subjectivity of the perception of space, which he expresses in one of the Lettres, it is impossible to say. It may be that it never occurred to him that the two opinions were discrepant; it may be that lie conceived it possible to reconcile them; and it may be that the idealistic view, which was published later than the other, implied the abandonment of the realism of the mind-stuff theory. As it is, we can only say that, as a metaphysician, Maupertuis has the apparently contradictory distinction of having given utterance, during the middle decade of the eighteenth century, to the favorite contentions of both the realism and the idealism of the nineteenth.