But that which gave Linnaeus so overwhelming an importance for his own time was the skilful way in which he gathered up all that had been done before him; this fusing together of the scattered acquisitions of the past is the great and characteristic merit of Linnaeus.
Cesalpino was the first who introduced Aristotelian modes of thought into botany; his system was intended to be a natural one, but it was in reality extremely unnatural; Linnaeus, in whose works the profound impression which he had received from Cesalpino is everywhere to be traced, retained all that was important in his predecessor’s views, but perceived at the same time what no one before him had perceived, that the method pursued by Cesalpino, Morison, Ray, Tournefort, and Bachmann could never do justice to those natural affinities which it was their object to discover, and that in this way only an artificial though very serviceable arrangement could be attained, while the exhibition of natural affinities must be sought by other means.
As regards the terminology of the parts of plants, which was all that the morphology of the day attempted, Linnaeus simply adopted all that was contained in the Isagoge of Jung, but gave it a more perspicuous form, and advanced the theory of the flower by accepting without hesitation the sexual importance of the stamens, which was still but little attended to; he thus arrived at a better general conception of the flower, and this bore fruit again in a terminology which is as clear as it is convenient; the terms monoecious, dioecious, triandrous, monogynous, etc., still used in the science, and the later-invented expressions dichogamous, protandrous, protogynous, etc., owe their origin to this correct conception of the sexual relations in plants. But there was one great misconception in the matter, which has not a little contributed to increase Linnaeus’ reputation. He called his artificial system, founded on the number, union, and grouping of the stamens and carpels, the sexual system of plants, because he rested its supposed superiority on the fact, that it was founded upon organs the function of which lays claim to the very highest importance. But it is obvious that the sexual system of Linnaeus would have the same value for the purposes of classification, if the stamens had nothing whatever to do with propagation, or if their sexual significance were quite unknown. For it is exactly those characters of the stamens which Linnaeus employs for purposes of classification, their number and mode of union, which are matter of entire indifference as regards the sexual function.
But though the notion that this artificial system has any important connection with the doctrine of the sexuality of plants is evidently due to a confusion of ideas, yet the progress of the science has shown, that Linnaeus’ sexual system did often and necessarily lead to the establishing of natural groups for the very reason, that the characters of the stamens which he employed are entirely independent of their function; for we must regard it as an important result of the labours of systematists, that those characters of organisms are shown to be of the greatest value for classification, which are entirely or in a very great measure independent of the functions of the organs. The error, which led Cesalpino to make the functional importance of the parts of fructification the principle of his division, reappears therefore in Linnaeus in another form; to find a principle of division, he turns to those organs, whose function appears to him the most important, but he takes his characters not from differences of function, but from the number and mode of union, which are of no importance for the sexual function. We meet with this error in Leibnitz and Burckhard, who are mentioned here merely to defend Linnaeus from the charge repeatedly brought against him by his contemporaries that he was indebted to these two writers for the idea of his sexual system. They erroneously found in the great physiological importance of the sexual organs a reason for deriving from their differences the principles of division that were to found a system; this error in theory Linnaeus shared with them, but they did not correct it in practice, as Linnaeus did, by confining himself to purely morphological features in working out his system. What the renowned philosopher[27] incidentally uttered in the year 1701 on the matter in question is moreover so unimportant and so indistinct, that Linnaeus could not gain much from it; what Burckhard[28] says on the subject in his often-quoted letter to Leibnitz (1702) is indeed much better, and comes near to Linnaeus’ idea; but it is a very long way from the hints there given to the completion of the well-articulated and highly practical system which Linnaeus constructed.
The botanists of the 16th century, and in the main even Morison and Ray, had in one-sided fashion devoted their chief attention to distinguishing species, Bachmann and Tournefort to the establishment of generic characters, while they neglected species; Linnaeus, on the contrary, applied equal care and much greater skill to describing both genera and species. He reduced to practical shape the suggestion which Bachmann had left to his successors, and so must be regarded, if not as the inventor, at least as the real founder of the binary nomenclature of organisms.
It is only fulfilling the duty of a historian to state the sources from which Linnaeus drew, but it would be a misapprehension to see in this any depreciation of a great man; it were to be desired that all naturalists would, like Linnaeus, adopt all that is good in the contributions of their predecessors, and improve or adapt it as he did. Linnaeus himself has repeatedly quoted the sources of his knowledge as far as they were known to him, and has in many cases estimated the services of his predecessors with a candour which never betrays a trace of jealousy, but often displays a warm respect, as may be seen especially in the short introductions to the several systems given in the ‘Classes Plantarum.’ Linnaeus could not only recognise what was good in his predecessors and occasionally make use of it, but he imparted life and fruitfulness to the thoughts of others by applying them as he applied his own thoughts, and bringing out whatever theoretical value they possessed. It was evidently this freshness of life that often misled his successors into believing that Linnaeus thought out and discovered everything for himself. We learn to appreciate the contributions of Cesalpino and his successors in the 17th century, and even of Kaspar Bauhin for the first time in the works of Linnaeus; we are astonished to see the long-known thoughts of these writers, which in their own place look unimportant and incomplete, fashioned by Linnaeus into a living whole; thus he was at once and in the best sense both receptive and productive, and he might perhaps have done more for the theory of the science if he had not been entangled in one grave error, which was more sharply pronounced in him than in his predecessors and contemporaries, that, namely, of supposing that the highest and only worthy task of a botanist is to know all species of the vegetable kingdom exactly by name. Linnaeus distinctly declared that this was his view, and his school in Germany and England adhered to it so firmly that it established itself with the general public, who to the present day consider it as a self-evident proposition that a botanist exists essentially for the purpose of at once designating any and every plant by a name. Like his predecessors, Linnaeus regarded morphology and general theoretical botany only as means to be used for discovering the principles of terminology and definition, with a view to the improvement of the art of describing plants.
We have hitherto spoken chiefly of the manner in which Linnaeus dealt with his subject in matters of detail; in his inner nature he was a schoolman, and that in a higher degree than even Cesalpino himself, who should rather be called an Aristotelian in the strict sense of the word. But to say that Linnaeus’ mode of thought is thoroughly scholastic is virtually saying that he was not an investigator of nature in the modern meaning of the word; we might point to the fact that Linnaeus never made a single important discovery throwing light on the nature of the vegetable world; but that would still not prove that he was a schoolman.
True investigation of nature consists not only in deducing rules from exact and comparative observation of the phenomena of nature, but in discovering the genetic forces from which the causal connexion, cause and effect may be derived. In the pursuit of these objects, it is compelled to be constantly correcting existing conceptions and theories, producing new conceptions and new theories, and thus adjusting our own ideas more and more to the nature of things. The understanding does not prescribe to the objects, but the objects to the understanding. The Aristotelian philosophy and its medieval form, scholasticism, proceeds in exactly the contrary way; it is not properly concerned with acquiring new conceptions and new theories by means of investigation, for conceptions and theories have been once for all established; experience must conform itself to the ready-made system of thought; whatever does not so conform must be dialectically twisted and explained till it apparently fits in with the whole. From this point of view the intellectual task consists essentially in this twisting and turning of facts, for the general idea of the whole is already made and needs not to be altered. Experience in the higher sense of investigation of nature is rendered impossible by the fact, that we are supposed to know all the ultimate principles of things; but these ultimate principles of scholasticism are at bottom only words with extremely indefinite meaning, abstractions obtained by a series of jumps from every-day experience, which has not been tried and refined in the crucible of science, and is therefore worthless; and the higher the abstraction is raised, the farther it withdraws from the guiding hand of experience, the more venerable and more important do these ‘abstracta’ appear, and we can finally come to a mutual understanding about them, though again only through figures and metaphors[29]. Science, according to the scholastic method, is a playing with abstract conceptions; the best player is he who can so combine them together, that the real contradictions are skilfully concealed. On the contrary, the object of true investigation, whether in philosophy or in natural science, is to make unsparing discovery of existing contradictions and to question the facts until our conceptions are cleared up, and if necessary the whole theory and general view is replaced by a better. In the Aristotelian philosophy and in scholasticism facts are merely examples for the illustration of fixed abstract conceptions, but in the real investigation of nature they are the fruitful soil from which new conceptions, new combinations of thought, new theories, and general views spring and grow. The most pernicious feature in scholasticism and the Aristotelian philosophy is the confounding of mere conceptions and words with the objective reality of the things denoted by them; men took a special pleasure in deducing the nature of things from the original meaning of the words, and even the question of the existence or non-existence of a thing was answered from the idea of it. This way of thinking is found everywhere in Linnaeus, not only where he is busy as systematist and describer, but where he wishes to give information on the nature of plants and the phenomena of their life, as in his ‘Fundamenta,’ his ‘Philosophia Botanica,’ and especially in his ‘Amoenitates Academicae.’ From among many instances we may select his mode of proving sexuality in plants. Linnaeus knew and lauded the services rendered to botany by Rudolph Jacob Camerarius, who as a genuine investigator of nature had demonstrated the sexuality of plants in the only possible way, namely, that of experiment. But Linnaeus cares little for this experimental proof; he just notices it in passing, and expends all his art on a genuine scholastic demonstration intended to prove the existence of sexuality as arising necessarily from the nature of the plant. He connects his demonstration with the dictum ‘omne vivum ex ovo,’ which Harvey had founded on an imperfect induction, and which he evidently takes for an a priori principle, and concludes from it that plants also must proceed from an ‘ovum,’ overlooking the fact that in ‘omne vivum ex ovo’ plants already form a half of the ‘omne vivum’; then he continues, ‘reason and experience teach us that plants proceed from an ‘ovum,’ and the cotyledons confirm it’; reason, experience, and cotyledons! Surely a remarkable assemblage of proofs. In the next sentence he confines himself at first to the cotyledons, which according to him spring in animals from the yolk of the egg, in which the life-point is found; consequently, he says, the seed-leaves of plants, which envelope the ‘corculum,’ are the same thing; but that the progeny is formed not simply from the ‘ovum,’ nor from the fertilising matter in the male organs, but from the two combined, is shown by animals, hybrids, reason, and anatomy. By reason in this and the previous sentence he understands the necessity, concluded from the nature, that is, the conception of the thing, that it must be so; animals supply him with the analogy, and anatomy can prove nothing, as long as it is not known what is the design of the anatomical arrangements. But the weakest side of this proof lies in the hybrids, for Linnaeus, when he wrote the ‘Fundamenta,’ knew of none except the mule; hybrids in plants were first described by Koelreuter in 1761, and these Linnaeus nowhere mentions; and what amount of proof can be drawn from the vegetable hybrids, which Linnaeus afterwards supposed himself to have observed, but which were no hybrids, we shall see in the history of the sexual theory; here we need only remark that he arrives at the existence of these hybrids from the idea of sexuality exactly as he arrived at that of sexuality from the idea of hybridisation. Then he goes on with his demonstration; ‘that an egg germinates without fecundation is denied by experience, and this must hold good therefore of the eggs[30] of plants—every plant is provided with flower and fruit, even where these are not visible to the eye’; with Linnaeus, of course, this is logically concluded from the conception of the plant or of the ‘ovum’; he alleges indeed certain observations as well, but they are incorrect. He continues, ‘The fructification consists of the sexual organs of the flowers; that the anthers are the male organs, the pollen the fertilising matter, is proved by their nature, further by the fact that the flower precedes the fruit, as also by their position, the time, the loculaments (anthers), by castration, and by the structure of the pollen.’ Here too the main point with Linnaeus is the nature of the male organs, and that we may know what this nature is he refers to a former paragraph, where we learn that the essence of the flower is in the anthers and stigma. Almost all his demonstrations consist of such reasonings in a circle and in arguing from the thing to be proved. And while the passages quoted show how much he did for the doctrine of sexuality, we find this sophistical style of reasoning still more copiously displayed in the essay entitled ‘Sponsalia Plantarum’ in the ‘Amoenitates’ (i. p. 77), and in a worse form still in the essay, ‘Plantae Hybridae’ (Amoen. iii. p. 29). That Linnaeus had not the remotest conception of the way in which the truth of a hypothetical fact is proved on the principles of strict inductive investigation is shown by these and many other examples, and by his enquiry into the seeds of mosses (Amoen. ii. p. 266), upon which he prided himself not a little, but which is really inconceivably bad even for that time (1750). It was not Linnaeus’ habit to occupy himself with what we should call an enquiry; whatever escaped the first critical glance he left quietly alone; it did not occur to him to examine into the causes of the phenomena that interested him; he classified them and had done with them; as for instance in his ‘Somnus Plantarum,’ as he called the periodical movements of plants. We cannot read much of the ‘Philosophia Botanica’ or the ‘Amoenitates’ without feeling that we are transported into the literature of the middle ages by the kind of scholastic sophistry which is all that his argumentation amounts to; and yet these works of Linnaeus date from the middle of the last century, from a time when Malpighi, Grew, Camerarius, and Hales had already carried out their model investigations, and his contemporaries Duhamel, Koelreuter, and others were experimenting in true scientific manner. This peculiarity in Linnaeus explains why men like Buffon, Albert Haller, and Koelreuter treated him with a certain contempt; and also why his strict adherents in Germany, who lived on his writings and were unable to separate what was really good in him from his mode of reasoning, came to make their own botany like anything rather than a science of nature. Linnaeus was in fact a dangerous guide for weak minds, for his curious logic, among the worst to be met with in the scholastic writers, was combined with the most brilliant powers of description; the enormous extent of his knowledge of particulars, and above all the pre-eminent firmness and certainty which distinguished his mode of dealing with systematic botany, could not fail to make the profoundest impression on those who judged of the powers of an investigator of nature by these qualities alone. One of his greatest gifts was without doubt the power which he possessed of framing precise and striking descriptions of species and genera in the animal and vegetable kingdoms by means of a few marks contained in the smallest possible number of words; in this point he was a model of unrivalled excellence to all succeeding botanists.
On the whole the superiority of Linnaeus lay in his natural gift for discriminating and classifying the objects which engaged his attention; he might almost be said to have been a classifying, co-ordinating, and subordinating machine. He dealt with everything about which he wrote in the way in which he dealt with objects of natural history. The systematic botanists whom he mentions in the ‘Classes Plantarum’ are classified then and there as fructists, corollists, and calycists. All who occupy themselves in any way with botany are divided into two great classes, the true botanists and mere botanophils, and it is very characteristic of his way of thinking that he places anatomists, gardeners, and physicians in the latter class. True botanists again are either mere collectors or systematists. To the collectors belong all who add to the number of known plants, also authors of monographs and floras, and the botanical explorers of foreign countries, whom we should now more courteously call systematists. By systematists Linnaeus understands those who occupy themselves with the classification and naming of plants, and he divides them into philosophers, systematists proper, and nomenclators; the philosophers are those who study the theory of the science on principles founded on reason and observation, and are subdivided into orators, institutors, erystics, and physiologists; the latter are those who discovered the mystery of sexuality in plants, and hence Malpighi, Hales, and such men are not physiologists in Linnaeus’ sense. The second class of systematists, the systematists proper, he distinguishes into orthodox and heterodox, the former taking the grounds of division exclusively from the organs of fructification, while the latter use other marks as well. In this manner Linnaeus treats every subject of which he has to speak, and wherever he can in short, numbered sentences, which look like descriptions of genera and species. His mind and character were fully formed in 1736 when he wrote his ‘Fundamenta,’ and he preserved his peculiarities of style from that time forward; we find the same modes of expression in the ‘Nemesis Divina,’ a treatise on religion and morals addressed as a legacy to his son. Where these peculiarities of manner and expression are suitable they make a favourable impression on the reader, as for instance in the short accounts he gives of the various systems in the ‘Classes Plantarum,’ a work in which Linnaeus was quite in his element; there he traces with a fine instinct the guiding principles of each system, pronounces upon its merits and defects, and sets it before the reader in numbered sentences of epigrammatic brevity. This manner is strictly adhered to in the ‘Philosophia’ also, and it has certainly helped not a little to withdraw the attention of his reader from his many fallacies in argument, especially his oft-recurring reasonings in a circle.
This remarkable combination of an unscientific philosophy with mastery over the classification of things and conceptions, this mixture of consistency in carrying out his scholastic principles with gross inaccuracies of thought, impart to his style an originality, which is rendered still more striking by the native freshness and directness, and not unfrequently by the poetic feeling, which animate his periods.