The History of Biological Theories

'If I have erred in giving to Natural Selection great power, which I am very far from admitting, or in having exaggerated its power, which is in itself probable, I have at least, as I hope, done good service in aiding to overthrow the dogma of separate creations.' (Darwin, The Descent of Man, p. 61.) THE Romantic Philosophy was not suddenly over- thrown. Its decay can be traced step by step from Hegel through Feuerbach and Strauss, to Schleiden, Lotze, Fechner and Lange, and it finally reaches its lowest point in exact science. The desire to philosophize remained, as did the public philosophical institutions, but these had to adapt themselves to the spirit of the times. To do this philosophy had to forgo her ancient privilege ; she could no longer prescribe the laws of thought. To her fell in return the glorious and honourable task of examining that foundation which is common to all the sciences ; of in- vestigating those things which science leaves untouched because held beyond investigation. Attention was now directed to the history of philosophy. Moreover, an interest in ethics arose, and there was an endeavour to reconcile uncertain 'faith' with certain 'knowledge', to examine the nature of religion, and so on.

There was a great contrast between the subject-matter of this philosophy and that of her proud forerunner, which had reigned since antiquity. Modern philosophy dealt only with the more doubtful forms of knowledge, nor was there any field of knowledge where she reigned supreme. She was ever at the mercy of scientific criticism. As a consequence the philosopher was no longer a specialist, for having to make use of the results of all the sciences he was at home in none. The exact scientist thought of him as of little account as quite without the right to meddle in the scientific domain. Philosophy and science were completely estranged.

This fall of the 'greatest of all the sciences' had its good side. Philosophy became democratic, while naturalists, on the other hand, freed from the fetters of philosophy, were able to investigate the subject for themselves they became philosophers. When we speak of scientific philosophy we are generally referring to the fact that Helmholtz wrote about Kant, Huxley about Hume, and so forth. But in such cases the scientific specialist, as such, was only in indirect relationship with philosophy. Greater importance should be attached to those cases where the scientist, almost without knowing it, ventured on philo- sophic ground; those cases, almost neglected by the philosophers, where, as the necessary result of his dis- coveries, he was led to formulate some universal law. To this type of philosophy belong Darwin's ethical, Huxley's and Haeckel's sociological views; Mach's, Darwin's, and Cuvier's scientific methodology, &c.

It is not clearly recognized even to-day that a new philosophy has arisen, one more natural than the older systems. We forget that, although a Darwin or a Haeckel did not fill two chairs, one of Science and one of Philosophy, yet their science cannot be separated from their philosophy. We must remember, too, that the ultra- modern reaction against science does not represent a return to ancient abstract metaphysics, but that we have here the beginnings of a philosophy founded upon natural science ; the works of Mach, Driesch, and Ostwald furnish a proof of this.

Herbert Spencer (1820-1904) is a typical example of the philosopher whose system is based on natural science rather than on his own inspiration. At first an engineer, and then an editor, he lived finally as an intellectual of independent means. With true English patience, he built up a new evolutionary conception of the world based on biology. He began his work before Darwin's time, at first in scattered articles, then in a work which was to include all that we know about life. The book is very dull, but is simply written. The ideas it contains are not deep, but they are sound and typically English.

This is not the place for a detailed examination of Spencer's philosophy; we will only note certain special characteristics of it. Spencer believed in God very much as Darwin did, who thought it idle to dwell on that sub- ject, since no certainty could come from such thinking, "t is also unnecessary ; man can do his duty without any belief in God. And yet Darwin did not want to play the atheist and attack old beliefs. That was not his view of his duty to society.

Spencer expresses practically identical ideas. He does not reject religion. Each system contains some fraction of the truth; it is difficult to say how much, for the real essentials of religious belief are unknowable. In practice, however, Spencer held that religion is something lower than science, suitable for people of small intelligence. He himself, with his greater knowledge, need pay little atten- tion to these unknowable things. The crowning feature of Darwin's philosophy is the idea of Natural Selection. Spencer discovered a still more fundamental cause of phenomena indestructible matter in unrestrained motion. Matter in motion leads directly to evolution, and this is

'An integration of matter and concomitant dissipation of motion ; during which the matter passes from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity; and during which the retained motion undergoes a parallel transformation.' (Collins, F. H., An Epitome of the Synthetic Philosophy , 1889, p. 47.) Life is only a particular combination of matter and motion. Living substance owes its 'life' to complicated and very unstable compounds ; the essence of life is adapta- bility. Power of adaptability is a measure of progress. The broadest and most complete definition of Life will be: The continuous adjustment of internal relations to external conditions. The amoeba, the multicellular back- boneless amphioxus, the monkey, the man, a pair of savages, civilized society all these, according to Spencer, illustrate the stages by which life adapts itself to its environment. The most fundamental living processes are growth, differ- entiation during development, the simple vital functions, adaptation, the separation of life into individuals, repro- duction, inheritance, and variation.

For Spencer, phylogeny only represents one aspect of the evolution of the world. We must believe in it, since the other alternative Creation by God is scientifically inadmissible. Spencer assumes, as does Darwin, that evolution is actually in progress in the living world, and his reasons for this belief are similar to Darwin's. It follows from the fact that we can formulate a 'natural' system of classification, from the resemblances between different animals, from embryology, from the facts of geographical and geological distribution. Spencer further assumes that this development is accelerated by external circumstances, climate, for example, and the living en- vironment, and also by inner conditions (as the 'lability' of the undifferentiated homogeneous condition).

He gives moreover the outline of a genealogical tree for plants and animals, classifying them according to their form and function. Looking through Spencer's Principles of Biology, and reading his monotonous questions and answers, we are not surprised that he was proclaimed in his own day as a universal genius. Here are examples of the questions which he felt able to discuss and to attempt to answer : 'Why should the growth of every organism be finally arrested ? Why should not all organisms, when supplied with sufficient materials, continue to grow as long as they live ?'

'Does Life produce Organization, or does Organization produce Life?' What are the conditions under which Genesis takes place ? How does it happen that some organs multiply by homogenesis, and others by heterogenesis V 'What is the original cause of this differentiation ? (of tissues in stems, petioles, &c.). Is it possible that this modification of cell- structure which favours the transfer of liquid towards each place of demand, is itself caused by the current which the demand sets up ? Does the stream make its own channel ?'

'Reference has been made more than once to those thickenings that occur where skin is exposed to unusual pressure and friction. Are these adaptations inheritable ? and may they, by accumulation through many generations, produce permanent dermal structures fitted to permanent or frequently recurring stress ?' All these questions and hundreds of others are formulated by Spencer, and to all he attempts an answer. This was a peculiarity of Spencerian philosophy, and typical of the school of thought which arose under his influence. They had an answer for every question. The thing which you ask is simply the result of certain mechanical, chemical, and physical factors, he says, and then he offers his ex- planation the one which seems to him the most likely in the given circumstances. He invents it, he does not deduce it from experiments or observations. It is true that Spencer did pursue definite biological studies, but these hardly bore any relationship to the substance of his explanations and his explanations far exceeded the range of his observations, both in quantity and in quality.

All the above questions, cited from Spencer, are so difficult that they can only be approached with the expenditure of the greatest intellectual exertion, and by an observer with a very deep insight into biological problems. Suppose, for example, it is desired to throw some light upon the origin of nerves. What a mass of observation and experiment, what a searching of the literature, what an amount of deep thought would be necessary! The problem is so vast that there are few investigators who would care to-day to attempt its solu- tion. Imagine how differently these questions would be attacked to-day, for we now realize that this relation between life and structure is one of the deepest and most obscure problems of modern philosophy. Spencer formu- lated the question and answered it, as he answered all similar problems, in a few pages, even in a few lines !

This method reduces to despair those who examine such works in search of philosophic truth. Yet it was the method of the whole of Darwinian biology and scientific psychology. Spencer was not the only one who used it. It is a logic which assumes that everything is already known. It acknowledges no mystery; it is surprised at nothing in the world. It follows the maxim nil admirari with an almost impossible consistency. Further, the very strong conviction existed that this method had been from time immemorial the scientific method. When the reaction against science began, people very justly complained of its aridity. How could it satisfy our desire for truth ? It was then seen that this superficial evolutionary method, which can explain everything in advance, is not characteristic of all science. Those in- vestigators who believed in the mystery the unfathom- able depths of Nature were the greatest investigators. When Newton looked at Nature as a great sea on whose shore he was only collecting scattered pebbles, he gave voice to a scientific spirit very different from the Spen- cerian one. The fact that great investigators like Kepler, Newton, Swammerdam, Pascal, van Helmont, Johannes Miiller were mystics, or became such, that they abandoned the hope of understanding by taking thought, and simply surrendered themselves to their inspirations all these are manifestations of a very different science from that which alleges that there is no mystery in Nature.

For Spencer, as for Darwin, the fundamental principle is: 'There is no absolute Reality, everything is a "result" ' ; the species is the result of natural selection, and this follows from the struggle for existence. This, in its turn, arises because of the general properties of living matter. These in turn are the results of the chemical and physical constitution of matter. These follow from the motion of their atoms. And even this motion has no absolute value, but is the product of subjective sensation, which is again only a result of what ?

Spencer's truths and falsehoods can be summarized as follows : (a) Belief in God. We know nothing of His nature, nor of the reason for His existence. He is probably not con- cerned with our world. The belief in Him is very likely only the result of man's astonishment at unusual occur- rences, an astonishment which has become fixed by inheri- tance. Nevertheless, believe! (ft) Evolution went on through millions of years in in- finite space. Every condition, as it arose, was the 'cause' of the ensuing one. But neither time, nor infinite space, nor the causal connexions between phenomena have any absolute existence; they are only ways of thought im- pressed on men by the inheritance of certain chance habits. Nevertheless, you must believe in the millions of years, in infinite space, in necessary causes !

(c) Be moral ! It is true that your love for your nearest and dearest has arisen during the rude fight for life, and that the law 'An eye for an eye, and a tooth for a tooth' contains a hundred times more truth than the command 'Whoever shall smite thee on thy right cheek, turn to him the left also'. Nevertheless, you must follow Christ, and live in the hope that the struggle for existence, the destruction of the weak and the rapid reproduction of the moral amongst men, will lead the world into the longed- for Paradise.

Some of the thinkers who, with Darwin and Spencer, were trying to form some picture of the evolution of the world, of religion, and of morality, turned to the study of the past. They endeavoured to build up, from a basis of moving atoms, the manifold variety of the present world. Zollner, Fechner, Preyer, Haeckel, Von Hartmann, were among these. Others were more concerned with mankind, and painted the advance in morality which the future was to bring. Among these were Fiske, Barrat, Williams, Leslie Stephen, T. H. Huxley, Alexander, Wallace, Clifford, Romanes, Benjamin Kidd, among Englishmen; Rolph, Wundt, Earth, Carneri, Vetter, and Buchner, among the Germans ; the Dane Hoffding ; the Russians Metschnikov and Novikov ; the Frenchmen Fouillee, Guyau, Ribot, and others.

The views held by these philosophers concerning the nature of human progress were not identical, but the majority accepted the idea of a struggle for existence, and they dealt chiefly with the transition from a nature 'red in tooth and claw' to one in which the higher moral laws where 'Love thy neighbour as thyself was the reigning command. Huxley was the first to realize the impossibility of any such transition ; he asserted that moral law is contrary to 'natural law 5 ; that morality and duty are at war with the animal instincts, and that ethics cannot possibly be only 'applied natural history'! These criticisms were aimed directly at Spencer's views. Huxley thus discovered the fundamental error in the evolutionary theory. While asserting that the origin of ethical ideas is to be explained by the new teaching about nature, it simply retained the moral principles characteristic of Christianity. In this respect evolutionary ethics were like evolutionary biology, and aimed at explaining the evolution of known ideas rather than at introducing new ones.

IN the early nineteenth century all German philosophy was in spite of differences between the different systems conservative in tendency. In certain details, it is true, a Goethe, Oken, Fichte, or Hegel might disagree with pre- vailing opinion, but, even when they seemed most icono- clastic, their whole thought was directed to the under- standing of existence as it is. The culminating point of this philosophy was reached by Hegel, and expressed by him in the well-known sentence 'What is reasonable is real, and all that is real is reasonable'. This belief was fatal to all hopes of influencing the world's events ; for, if all that exists is 'reasonable' (i.e. a manifestation of reason), any effort to enrich or to ennoble the world is meaningless! Hence Hegel became a pillar of conservatism, and his point of view was repudiated by the 'Young Germany'. As the movement to the Left began, and this ever-growing Radicalism brought with it a belief that all reasonableness and all truth must be relegated to a far-distant future, there arose a great discontent with this view of existence.

'Everything that is, is unreasonable' was the cry of the new agitators, and they held that it was the task of science to improve and to revivify the world. By exact science they meant Positivism in France, but in Germany Materialism and Darwinism. One result of this tendency was that the most varied sciences and other spheres of thought now began to replace their earlier rationalistic systems by some form of Darwinism. Like an oncoming flood, the conviction spread that no science, except physics, chemistry, and the Darwinian con- ception of natural history, contained any absolute truth, but that all other branches of knowledge would have to be revised and remodelled, basing themselves on this, the

only exact knowledge we have. Kant's axiom, that in every science only that is exact which can be mathemati- cally expressed was adopted with but slight change. In- stead of mathematics were put physics, chemistry, and natural history. The ideas of struggle for existence, natural selection, heredity, atavism, degeneracy, were separated from biology, accepted as of real value, and introduced into the most varied fields of intellectual activity. Darwin himself helped to bring this about when he endeavoured to account for such diverse phenomena as the origin of birds, of religions, of the instinct of bees, of flowers, and of colours, by his theory of natural selection. If such heterogeneous things could be explained by this theory, why should it not be able to account for the origin of chemical combinations, or of the European States ? It is not possible to examine all the cases where there was an endeavour to transplant Darwinism into the most diverse fields of knowledge. We can only indicate some of the most important among them.

Chemistry, Petrography, Astronomy. Many attempts were made to introduce the Darwinian theory into chemistry. J. C. F. Zollner, the well-known physicist and spiritualist, declared that : 'Positive and negative electricities are the fundamental units of matter, and in course of time all chemical elements were formed from them. These changes were the result of mutual reactions, and new elements were formed in response to given mechanical conditions. New species of plants and animals arise in a similar way. They are the result of natural selection and arise as adaptations to complex conditions of existence' (Vber die Natur der Kometen, Leipzig, 1873).

L. Pflaunder, Innsbruck, studying the origin of certain chemical compounds by dissociation, saw an analogy between these reciprocal reactions and natural selection (1867). C. Nageli, the well-known Munich botanist, believed that all the elements in each of MendeleefFs groups arose in the same epoch and in the same region of the universe ; that the heavier elements were formed before the lighter ones; that the group to which platinum, iridium, and osmium belong arose first, and that hydrogen was the last to be formed (1884). Other hypotheses con- cerning the origin of the elements and the struggle for existence of the molecules were published by W. Preyer, Viktor Meyer, W. Crookes, C. Wendt, and others.

Darwinism was also used to explain the origin of moun- tain ranges. J. Walther, the geologist, tried to prove that some minerals are less susceptible than others to the action of the environment. These have survived, and form the most ancient mountain groups of to-day; others were more easily destroyed by the action of rain, of acids, of mechanical forces, and hence took little part in such forma- tions (1895). V. Meunier (1871) and the Freiherr du Prel (1874) transferred the idea of the struggle for existence to the heavenly bodies ; they supposed that it was raging at the time when the nucleus of the solar system was being formed by condensation from primeval substance; stars incapable of a separate existence collided and were destroyed, until finally only those moving in a suitable manner survived.

The subject of psychology will be dealt with in a separate chapter ; here we shall only refer to the attempt to explain colour vision as the product of evolution. H. Magnus developed the idea that men were originally colour blind, and that they first learned to distinguish red, then yellow, then light green, and finally blue and violet ; he thought that a time may come when ultra-violet light will also be visible to the eye (1877). Before the time of Magnus, Gladstone and Geiger had asserted that the ancients (Homer, for example) could not distinguish blue from black, nor green from grey. They referred to the writers of the Bible, to Aristotle and other writers of antiquity, to obtain evidence which would support this

view, but the theory did not long survive, and it was criticized even by Darwinians as E. Krause. The Darwinian theory became of greater importance in the science of language than in the above-mentioned branches of knowledge. The methods of comparative philo- logy and comparative biology were already very similar. The morphologists compared the structure of different organisms, determined what they had in common, and so created 'types'; the investigator of language com- pared the words of various languages to discover common roots. Just when morphological speculation was most flourishing Fritz Bopp (1791-1867), the originator of the science of comparative philology, began his work; he based his science on the discovery of common roots (e. g. the words am, dsmi, ei/u', sum, suis, im, jesmi). The differences of opinion which arose about the development of language resembled the biological discussions concerning preforma- tion and epigenesis. Some, among them Bopp himself, asserted that the words of existing languages were evolved from definite roots, and that the changes were regulated by laws inherent in the roots themselves; others (in- cluding Schlegel) stoutly affirmed that words have arisen by a gradual blending of sounds (agglutinization) i.e. by a sort of epigenesis. Under the influence of those investi- gators, and of Herder, Humboldt, and Hegel, the origin of language became a favourite philosophical theme. Thus when Darwin appeared with his views, many philosophers fitted their ideas into his theories.

The science of language was steered into the Darwinian current by Schleicher (1821-1868), Haeckel having first drawn his attention to The Origin of Species. He published a pamphlet in which he stated that the idea voiced by Darwin was by no means new to those engaged in the study of speech. They had long been studying the evolu- tion of language. They could, however, now learn from the naturalists that only definite objective facts and con- elusions derived from them are of any value in this field of research. Tor the study of language (philology) is really a sort of natural history.' (Schleicher, Die Darwinsche Tbeorie und die Sprachwissenschaft, Weimar, 1863.)

*I well know how much I owe to the study of such works as Schleiden's on botany, and Vogt's physiological letters ; how much these works influenced my ideas on the nature and life of language. . . . From these books I first obtained my knowledge of evolution. The naturalists teach us how important it is to study facts based on unbiased observations, and the conclusions derived therefrom. Languages are natural growths. They have arisen independently of the will of man ; they grow and develop according to definite laws and they finally decay and die out. Hence they exhibit the characteristic features of a living organism. . . . The science of language is therefore a natural science.'

For this reason, Darwin's theory and Haeckel's monism are relevant in the science of language too. We need only to alter the terminology a little. We call the genera belonging to one species the languages of one group ; sub-species are dialects, varieties are idioms. Biological units are individuals differing in slight degree ; each man's speech is individual too, differing slightly from that of all other men. We can construct genealogical trees for languages, as we do for animals. Languages develop, as their common roots testify, from one original stock. In course of time, languages developed and their number increased, until the tongues of the present day were evolved. This differentiation was brought about by varia- tion in the conditions of life, and modern languages, in spite of great differences, still carry with them the direct evidence of a common origin.