Popular Science Monthly/Volume 71/December 1907/The Place of Linnaeus in the History of Science
|THE PLACE OF LINNÆUS IN THE HISTORY OF SCIENCE|
By Professor ARTHUR O. LOVEJOY
WASHINGTON UNIVERSITY, ST. LOUIS
THE recent celebrations of the bicentenary of Linnæus's birth had one sort of appropriateness in somewhat higher degree than is usual in such commemorations: they helped pay the debt of posterity to one of the great figures of the history of science in the currency that he had especially valued. For Linnæus had very markedly the last infirmity of noble mind. Faniam extendere factis was his chosen device, which he often prints, with a pride justified only by the event, upon the title-pages of his books; and his biographers are at one in emphasizing the intensity of his desire for fame. It was, indeed, the solid and enduring fame of the productive scholar that he sought, not the applause of the groundlings; his ambition was to link his name to some lasting and imposing part of the ever-enlarging fabric of organized knowledge, and thereby to take rank among the acknowledged masters of those who know. That this ambition, large as it was, has been more than fulfilled, is sufficiently evidenced by the worldwide commemoration of this anniversary of his birth—even in cities of the western continent which were themselves non-existent when he came into the world. No naturalist of his century, and few naturalists of any period, have so universal a popular reputation, or are, by so nearly common consent, given a place among the immortals not far removed from Copernicus, Galileo, Descartes, Leibniz and Newton—to mention only his predecessors. Yet, when seriously scrutinized, Linnæus's position in the history of science is a peculiar one. With his name there is commonly associated no epoch-making hypothesis, not a single important discovery, not one fundamental law or generalization, in any branch of science. The forty years of his active life constitute a period prolific in fruitful hypotheses and signalized by the original enunciation of a number of valid generalizations of the first order of importance; of none of these was he the author. To go no farther than the biological sciences which Linnæus professed: Before 1750, Daubenton and Buff on had begun to establish the new science of comparative anatomy and were making known the striking homologies which run through the structure of all species of vertebrates; between 1745 and 1751 Maupertuis had promulgated, and defended with effective arguments, the theory of the transformation of species; in physiology, the significant fact of the independent irritability of muscle was discovered by Haller in 1757; in embryology, the doctrine of epigenesis was revived and finally established by Caspar Friedrich Wolff in 1759. As for the science of botany, the foundations had been laid, and the general outlines and principles which were to continue to rule during Linnæus's time had been established by the end of the preceding century. The founder of modern scientific botany is Cesalpino (1583). In microscopic plant anatomy and histology, the investigations and descriptions which were to underlie the science for something like a century had been made before Linnæus's birth by Grew, Malpighi, Leeuwenhoek. In plant physiology, the role of the sap had been studied by Malpighi, and the fundamental facts made clear by Hales in his "Vegetable Staticks," 1727; the function of pollen in the fecundation of seeds had been shown by Camerarius before the end of the seventeenth century; the existence of the sexual distinction in plants had been insisted upon by a long succession of botanists, English, German, Italian and French; and during Linnæus's lifetime the physiological rôle of leaves was being made clear (so far as the condition of chemistry at the time permitted) by the philosopher Christian Wolff and by Bonnet.
Not only is all this true, but it is also a fact that Linnæus has been not absolutely unfairly represented, by one of the historians of modern science, as an obstacle to the scientific progress of his time. President White, in his "Warfare of Science and Theology," after speaking of certain anticipations of nineteenth century conceptions by DeMaillet, Eobinet and Bonnet, remarks:
Yet, though in the intellectual movement of his time Linnæus was an extreme conservative, if not something of an obscurantist; though he was far surpassed by several of his contemporaries in that kind of insight and constructive power which leads to the discovery of the great general laws of nature; and though the heavy pioneer work even in his favorite science had been done before his time by the great investigators of the end of the seventeenth century—though all this is the case, none of these others equals Linnæus in popular repute or in accepted standing in the history of science. I can not say that I think this altogether just, though if it be less than just, the proper inference is not that we should praise Linnæus less, but some of the others more. I have, however, mentioned these things, not for the sake of measuring out Linnæus's glory with a hopeless attempt at exact distributive Justice, but for the sake of defining more precisely, and in terms of explicit contrast—which is the only illuminating way of defining—the nature and limits of Linnæus's contribution to the evolution of the sciences. He was the one naturalist of first eminence whose work lay entirely, or almost entirely, within the sphere of descriptive and classificatory science. His rôle is precisely described by the term which he himself employed; he was not the originator of, nor a great discoverer in, botany, but he was the "reformer" of that science, reformator botanices, and in a less degree, of zoology. And in using this term to describe his work, the emphasis should be upon the "form." He was, in other words, an unsurpassed organizer, both of scientific material and of scientific research; he introduced form and order, clearness and precision, simple definitions and plain delimitations of boundaries, into sciences previously more or less chaotic or confused or impeded with cumbrous and inappropriate categories and terminology.
This reformation was the result of the three improvements effectually introduced by Linnæus and indissolubly associated with his name. The first, which seemed the most impressive and did most to establish his fame among his contemporaries and for several generations thereafter, was really the least permanent and the least valuable of his contributions: this was the introduction of a new artificial system of classification, based, in the botanical field, upon the differences of the sexual organs of plants. The second was the introduction of the binomial nomenclature, the system of so-called "trivial" names, which put a final end to the hopeless length and complexity of botanical and zoological specific names, and sharply differentiated the naming of organisms from the description of them. The third and, I suppose, the most useful as well as most durable of all of Linnæus's improvements, was the establishment of a new descriptive terminology in botany, the drawing up of a set of terms, each with clearly defined meaning, for designating concisely the distinguishable parts and organs of plants, and the several types of form of which each part is susceptible. By these means Linnaeus imposed order and harmony upon a realm that had hitherto suffered much from anarchy; he gave a common language to those who tilled its fields, and provided them with working tools of an unprecedented simplicity and convenience. And where he thus introduced order he also, as a natural consequence, introduced abundance. Both directly and indirectly Linnaeus immensely augmented the store of concrete botanical information. The science thus simplified and systematizcd and given a convenient means of expression became vastly more attractive and interesting; in particular. it came to be a field in which many minds, of all orders of ability, could do useful work, and could make their work dovetail into the work of others in such wise that each was conscious of having contributed a definite part to an immense and impressive edifice of an intelligible outline and design. Alike by the superior convenience of his classification, nomenclature and terminology, by the force and serious enthusiasm of his personality, and by the example of his admirably exact observation, Linnaeus stimulated a prodigious amount of ardent and careful botanical and zoological research on the part of others. His own pupils went out, literally by the score, not only over Europe, but to the uttermost parts of the earth, to collect new species and study geographical distribution. A number of these young enthusiasts, whose names are honorably recorded by one of Linnæus's biographers, lost their lives in these expeditions. The eight volumes of Linnæus's "Amœnitates Academicæ" contain 186 dissertations by almost as many of his pupils, the subject and treatment being in nearly every case suggested, and the results corrected, by Linnæus himself; most of these contain contributions of valuable—and many contain what were in their day highly original—botanical, zoological or mineralogical data. Nor was the effect of Linnæus's simplification and systematization of botany limited to the setting of other and younger men of science to work. His efforts also notably increased the general vogue of botany, as a result of which it long enjoyed an exceptional popularity and an unusual amplitude of endowment among the sciences. This aspect of Linnæus's work is effectively presented—all the more effectively for a considerable touch of rhetorical exaggeration—by Magdeleine de Saint-Agy in his continuation of Cuvier's "Histoire des Sciences Naturelles" (1845); the passage illustrates so well, if not precisely, what Linnæus did, at least what he had the credit of doing, that I venture to translate it.
Yet it is important, in the interest of historical truth, to point out that even in these things which constitute his peculiar work—specifically, in his reformation in taxonomy, nomenclature and terminology—Linnæus was in no respect a pioneer or an originator. It was his good fortune to be able to develop and carry through suggestions and outlines of procedure which had been made by his seventeenth-century precursors, and to exploit to the utmost an abundant legacy of botanical knowledge, methodological ideas, and botanical interest which had come down to his generation, Nothing, indeed, could be farther from the truth than the notion which appears to have wide popular currency, that there was little botanical study or knowledge worth mentioning before Linnæus. It is, on the contrary, eminently a case where vixerunt fortes ante Agamemnona. Any who suppose sixteenth and seventeenth century botany to be a negligible quantity will find it instructive to examine the shelves of the library of the Paris Jardin des Plantes; or to remember that Jean Bauhin's "Historia universalis plantarum" (1660), consisting of forty books, contained descriptions of some 5,000 plants, with 3,500 figures, and cost the equivalent of about $18,000 to produce—or that, a little later, Ray's "Historia plantarum generalis" gave a classified arrangement and description of 11,700 plants. And while Linnæus assuredly gave, as has been said, a great impulsion to the popular and fashionable interest in botany and zoology, it was an interest which was extremely well developed before his time—which, in fact, made his own work and his own contemporary fame possible. It was not through his influence first that states and monarchs learned the propriety of establishing botanical gardens. The Jardin royal du Louvre, for example, was established by Henri IV. in 1590, and the Jardin des Plantes was founded in 1626. By the middle of the seventeenth century both public and private gardens, often with scientific establishments connected with them, were becoming fairly common. And, as I have said, the particular reforms through which chiefly Linnæus achieved his results were essentially not discoveries nor innovations of his own. It will be profitable to note briefly the earlier history of the ideas involved in each of these three reforms.
First, then, concerning classification. Linnæus's great precursors in this field were Cesalpino, Ray and Tournefort. Cesalpino was a sixteenth-century enthusiast of the revival of the Peripatetic philosophy; and it was largely the influence of a fresh study of Aristotle's logic and metaphysics which led him to condemn all the then customary ways of classifying and naming plants—by their medicinal or other practical properties, the localities in which they are found, and the like—as being based upon mere "accidentia" and to insist upon the necessity of an orderly arrangement by genera and species founded upon the presence of common visible characters. In his selection of the characters by reference to which the primary division into genera is to be made, he is guided by considerations drawn from the Peripatetic metaphysics. The essential character of any "substance" consists in its "end" or "function" (opus). The distinctive function of the vegetative soul is twofold, nutrition and "the generating of its own like"; the latter is the higher, and it also presents more numerous and sensible points of variation in different plants. It follows that plants should be divided into genera according to the differences in form and arrangement of their "fruit-producing" organs (ex modo fructificandi, ex propriis quae fructificationis gratia data sunt). "With this as a starting-point, Cesalpino proceeds to a series of successive divisions in which 840 species find place. Ray's contributions to taxonomy had less success and influence than those of Cesalpino and of Tournefort, and are therefore historically less significant; but concerning their intrinsic merit it is worth while quoting the recently expressed opinion of a living botanist of high authority, who places Ray as a taxonomist above Linnæus himself. It was the English naturalist, says M. Bonnier, who must be regarded as "the true founder of the natural method"; "he it was who first enunciated the essential principles on which the classification of plants ought to be founded, who made clear the difference between phanerogams and cryptogams, who discovered the distinction between monocotyledons and dicotyledons, who established in a rational manner the main divisions of the vegetable kingdom."
At a natural method Tournefort made no more attempt than did Linnæus. But of the principles and purposes of a good artificial classification he had an entirely clear comprehension; and of such a classification of then known plants he gave an elaborate and imposing exemplification. Of what a "natural system" would be, if one could attain to it, Tournefort, like his Swedish successor, had a conception rather mystical or theological than scientific; it would be an arrangement of animals and plants according to the "natural" or "essential" species established by "the Author of Nature." But for his actual scheme he recognizes plainly that the primary criteria are the practical ones of simplicity and convenience. A genus or species, for botanical purposes, is "simply the whole group of plants that have a character in common which essentially distinguishes them from all others"; and in the selection of the characters by means of which the division is to be made we may ignore metaphysical considerations. Tournefort observes (apparently reflecting upon Cesalpino): "Let no one say that, since the sole end of nature is the production of fruit, we ought to consider the fruit as the noblest part of the plant. The intentions of nature are not in question here, nor yet the nobility of the several parts; what concerns us is to find means of distinguishing different kinds of plants with the greatest possible clearness. If the least of their parts served this purpose better than those which are called the noblest, it would be necessary to prefer the former." Tournefort's actual classification, based upon the characters of both flowers and fruit, realized these ideals of serviceableness, convenience and consistency somewhat imperfectly. But it was the ruling one in the science for nearly half a century; and, accompanied as it was by careful descriptions of an immense number of species, it furnished a model upon which Linnæus needed only to improve.
The Swedish naturalist's simplification of nomenclature was not only approximated, but  Later Tournefort, a botanist of greater eminence and influence, though he followed this example only partially, insisted emphatically upon the need for a reform and simplification of nomenclature. So far as the names of genera are concerned, he observes that "one ought to make a very great difference between naming plants and describing them"; he remarks that "nothing is so unfavorable to the reformation of botany as the habit which has come to prevail of judging of the nature of plants from the etymology of their names," and recommends that generic names be formed exclusively "out of words that have of themselves no meaning"; and he ridicules the long descriptive names then used by many botanists. The designations of species, however, he considers, should consist of the name of the genus plus a clear descriptive indication of the differentia of the species; and since the latter can not always be expressed by a single word, Tournefort does not employ a uniformly binomial nomenclature. But from the reforms already recommended and adopted by the great botanist of the preceding generation to the Linnæan system of "trivial" specific names, the step was easy and obvious.anticipated, by at least one of his predecessors. As Professor Underwood has pointed out, the binomial system of naming plants was used by Cornut in his "Canadensis Plantarum Historia" as early as 1635.
Again, in providing botany with an appropriate set of terms for the concise indication of the parts and organs of plants, Linnæus was merely following the suggestion and extending the work of another great seventeenth-century reformer in science. It was Joachim Jung—a naturalist whose intellectual force so impressed his contemporaries that Leibniz did not hesitate to compare him to Aristotle, or Comenius to liken him to Euclid—who was the father of comparative morphology in botany, who introduced into the study of the characters of plants real thoroughness and precision, who insisted upon the need for a system of clear, unambiguous organographic terms, and who himself devised and introduced a number of the terms still in use. His "Isagoge Phytoscopica" (1622) was wholly devoted to urging and exemplifying this reform; all the principal parts of plants are distinguished and defined with admirable clearness, their possible variations of form noted, and new and explicit names for these variations proposed. Jung seems, for example, to have been the first to employ the terms petiole or pedicule and perianth; to classify the arrangements of leaflets as digitate and pinnate, and to subdivide the latter sort into paripinnate and imparipinnate; to speak of the disposition of leaves as opposed, alternate, triangulate, etc. The descriptive terminology of botany has, of course, since expanded immensely; but the credit for the origination of the language of that science must unquestionably be assigned to Jung and not to Linnæus.
It still remains true, however, that Linnæus united these three reforms in a single system; that he carried each of them farther than had any of his predecessors; and that by the force of his personality he was able to gain for them a general acceptance which they had hitherto lacked. Though we must, therefore, make some deduction from the current view of the originality of Linnæus's work as reformer and organizer of botanical knowledge, we need not on that account greatly lower our estimate of its actual importance in the history of science. And yet we must, to get a just picture, always remember the character, as well as the magnitude, of that work; we must remember that it was, all but exclusively, form, system, nomenclature and specific observations that Linnæus contributed to the biological sciences, rather than fundamental discoveries, pregnant hypotheses or illuminating general ideas. Even in the presence of the impressive picture of the solid results of Linnæus's life-work drawn by the French historian of these sciences, one can not help recalling a caustic remark—which I have already elsewhere cited—of Linnæus's contemporary, Maupertuis, then president of the Berlin Academy of Sciences. Maupertuis spoke of zoology; but we may generalize his observation: "All these treatises on plants and animals which we as yet have," he says (about 1750), "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 organism, but with the general processes of nature in the production of organisms and the conservation of them." Towards making natural history a veritable science in this sense Linnæus did relatively little; but it is not quite true to say that he did nothing at all. Towards the discovery or the establishment of two generalized laws respecting the processes of nature in the production and the perpetuation of vegetal organisms Linnæus made some contribution; and of these something ought briefly to be said, the more because they are often neglected in the accounts of Linnæus's work.
1. Although, as has been remarked, the fact of sexuality in plants had been noted by a number of great naturalists before 1718, the doctrine was not, in Linnæus's youth, at all generally accepted. It was possible at the beginning of the eighteenth century for a botanist so eminent as Tournefort to combat and ridicule the idea; and for the Imperial Academy of Sciences of St. Petersburg, so late as 1759, to offer a prize for the best argument either for or against the doctrine of sex in vegetables. Linnæus gave the weight of his authority, as well as of some new experimental evidence, to the affirmative of this question. By him the fact may be said to have been finally established; and by his sexual system of classification the idea was made a familiar and fundamental common-place of even popular botanical knowledge.
2. By his doctrine of the "Prolepsis Plantarum" and "Metamorphosis Plantarum"—which one of his disciples declared to be "the most subtle discovery of any which can be put forward by the investigators of nature in our age," but which there lacks space to set forth in its details—Linnæus began that theoretical reduction of the several parts of a plant to modifications, under special conditions, of a few simple organs, which Goethe was to elaborate and carry much farther in his "Metamorphose der Pflanzen" (1790). Goethe makes due acknowledgment of his debt to Linnæus (who was his constant study in his early years) in that treatise, the place of which in the history of botany is well known. Contemporary botanists would, I suppose, incline to question whether this theory has done greater service or harm to the progress of their science. Its chief value lay in its tendency to suggest the idea of the unity of type—and eventually the idea of the common derivation through processes of transformation—of different species. Both of these ideas were far from the mind of Linnæus; with him the theory took the form only of the purely specific doctrine of the interchangeability of leaf and flower under varying conditions of nourishment, or at different phases of the individual plant's growth.
In these two instances, then, Linnæus made some contribution to the unification, as well as to the augmentation, of knowledge. Yet his lack of any penetrating insight into the larger relations of biological facts and the absence in him of any sound grasp of scientific method, disqualified him from taking a place among those who have materially enriched our stock of the ideas and categories which may be used in the interpretation of nature. His emphasis upon the static aspects of the world of living organisms—upon the fixed characters of species—and upon the descriptive rather than explanatory business of scientific inquiry made his influence, on the whole, an obstacle to the development and diffusion of those evolutional ideas which were already stirring in a number of minds of his generation. His ineptitude in the more philosophic part of the naturalist's work could not be better shown than in the one treatise in which he attempts a broad philosophical view and a wide correlation of organic phenomena. This writing, "Œconomia Naturæ," which was greatly admired by his contemporaries, points out in how diverse and complicated ways organisms of different species interact with one another, and are reciprocally adapted to one another, as well as to the conditions of survival in their environment. In dilating upon this Linnæus may be said to call attention, more than a century before Darwin, to the reality and importance in nature of the struggle for existence between species; for he shows how every kind of organism has its natural enemies, with which it keeps up an unceasing warfare or competition, as a result of which the otherwise excessive multiplication of each kind is prevented and the equilibrium of nature is preserved. But all these Just observations lead Linnæus to nothing more useful to science than the quam pulchre! We are invited to see in the arrangement whereby the lion saves the lamb from the Malthusian inconvenience of over-multiplication simply an evidence of design in nature. It never occurs to the great naturalist to consider that, as Maupertuis put it, "since only those creatures could survive in whose organization a certain degree of adaptation was present, there is nothing extraordinary in the fact that such adaptation is found in all the species that now exist." Looking upon the same general class of facts as those which were to be considered by "Wallace and Darwin, Linnæus finds in them nothing but the occasion for the wholesale introduction of teleological considerations, in place of causal explanations. In setting the example of such a proceeding, Linnæus certainly did much to hold biology back from its proper methods and its proper problems. In this, as in his general failure to take a philosophic view of his subject, his mental attitude was peculiarly uncongenial to the greatest intellect—if not the greatest botanist—of those whom he largely influenced. Goethe kept up a lifelong protest against all purely descriptive science and all introduction of teleological notions into the explanation of natural phenomena. And it is from Goethe in his old age that I may, in closing, quote a somewhat severe, but not unilluminating, remark upon the master of the poet's early botanical studies; since it contains a sort of philosophical pun, it is necessary to give it in the German:
Yet if Linnæus was not qualified to lead biology into the promised land of that "higher insight"—if he even somewhat delayed its progress thither—it must still be said that he left all the sciences with which he dealt incomparably better provisioned for that progress than they would have been without his work. He left to them an intensified ardor for the scrutiny of all the phenomena of nature, a better command of their own materials, and a greatly enriched and better ordered store of those concrete facts out of which, in time, scientific generalizations often almost spontaneously develop, and by which they must always eventually be tested.
- Revision of a paper read before the Academy of Science of St. Louis at its celebration of the two hundredth anniversary of the birth of Linnæus.
- "Entdeckung der wahren Ursache von der Vermehrung des Getreydes," 1718. Cf. also his "Vernünftige Gedanken von dem Gebrauche der Theile in Menschen, Thieren und Pflanzen," 1725, Pt. II., chap. 5.
- Récherches sur l'usage des feuilles," 1754.
- These figures are taken from Hoefer's "Histoire de la Botanique," 1872.
- 1519-1603. Cesalpino was a physician to Pope Clement VIII., and professor of materia medica and director of the botanical garden at Pisa. He was the original discoverer of the circulation of the blood; the doubts which have been sometimes expressed whether he anticipated Harvey's conception in its fullness have been shown to involve the overlooking of an explicit passage in Cesalpino's "De Plantis" (1583): cf. Du Petit-Thouars in "Biographic Universelle," s. v.
- "De Plantis" (1583), Lib. I., Cap. XIII.
- "Historia Plantarum," 1686.
- "Le monde végétal," 1907, pp. 48-9.
- "Elemens de la Botanique," 1694; the Latin version of this, "Institutiones Rei Herbariæ," with some alterations, appeared in 1700.
- "Underwood in Torreya, October, 1903, and in Popular Science Monthly, June, 1907. A brief and often binomial nomenclature is ascribed by Bonnier to Belon (d. 1574), whose work I have not seen.
- "Elemens de Botanique," 1694, pp. 14, 36, 38.
- Born in Lübeck, 1587, (lied at Hamburg, 1657. He published comparatively little, and his principal botanical works were brought out by friends after his death.
- The assertion that Jung was not anticipated in the use of these terms rests upon the authority of Hoefer, "Hist, de la Botanique."
- The poet himself wrote in his "Geschichte meines botanischen Studiums" (1817): "After Shakespeare and Spinoza, it was Linnæus who had the greatest influence upon me—chiefly, indeed, by the opposition that he provoked. For when I strove to make my own his sharp, clear-cut divisions and his apt and serviceable but often arbitrary laws, an inner conflict arose in me: what he sought forcibly to hold apart, the deepest need of my nature made me wish to bring back to unity."
- "Aphoristisches," Weimar-Ausg., Teil II., Bd. 6, § 356 (1829); cited by Wasielewski in his "Goethe und die Descendenzlehre."