If the thought of the teleological structure of nature was to be reformed in the sense of a naturalistic world conception, the purpose-adjusted formation of the organic world had to be explained in the same fashion as the physicist or the chemist explains the lifeless processes. When a magnet attracts iron shavings, no physicist will assume that there is a force at work in the magnet that aims toward the purpose of the attraction. When hydrogen and oxygen form water as a compound, the chemist does not interpret this process as if something in both substances had been actively striving toward the purpose of forming water. An explanation of living beings that is guided by a similar naturalistic mode of thinking must conclude that organisms become purpose-adjusted without anything in nature planning this purpose-conformity. This conformity comes to pass without being anywhere intended. Such an explanation was given by Charles Darwin. He took the point of view that there is nothing in nature that plans the design. Nature is never in a position to consider whether its products are adequate to a purpose or not. It produces without choosing between what is adequate to a purpose and what is not.
What is the meaning of this distinction anyhow? When is a thing in conformity with a purpose? Is it not when it is so arranged that the external circumstances correspond to its needs, to its life conditions? A thing is inadequate to purpose when this is not the case. What will happen if, while a complete absence of plan in nature characterizes the situation, formations of all degrees of purpose-conformity, from the most to the least adequately adapted form, come into existence? Every being will attempt to adapt its existence to the given circumstances. A being well-adjusted to life will do so without much difficulty; one less adequately endowed will succeed only to a lesser degree. The fact must be added to this that nature is not a parsimonious housekeeper in regard to the production of living beings. The number of germs is prodigious. The abundant production of germs is backed up by inadequate means for the support of life. The effect of this will be that those beings that are better adapted to the acquisition of food will more easily succeed in their development. A well-adapted organic being will prevail in the strife for existence over a less adequately adjusted one. The latter must perish in this competition. The fit, that is to say, the one adapted to the purpose of life, survives; the unfit, that is, the one not so adapted, does not. This is the “struggle for life.” Thus, the forms adequate to the purpose of life are preserved even if nature itself produces, without choice, the inadequate side by side with the adequate. Through a law, then, that is as objective and as devoid of any wise purpose as any mathematical or mechanical law of nature can be, the course of nature's evolution receives a tendency toward a purpose-conformity that is not originally inherent in it.
Darwin was led to this thought through the work of the social economist Malthus entitled Essay on the Principle of Population (1798). In this essay the view is advanced that there is a perpetual competition going on in human society because the population grows at a much faster pace than the supply of food. This law that Malthus had stated as valid for the history of mankind, was generalized by Darwin into a comprehensive law of the whole world of life.
Darwin now set out to show how this struggle for existence becomes the creator of the various forms of living beings and that thereby the old principle of Linnaeus was overthrown, that “we have to count as many species in the animals and vegetable kingdoms as had been principally created.” The doubt against this principle was clearly formed in Darwin's mind when, in the years 1831–36, he was on a journey to South America and Australia. He tells how this doubt took shape in him.
When I visited the Galapagos Archipelago during my journey on H.M.S. Beagle, at a distance of about 500 miles from the shores of South America, I saw myself surrounded by strange species of birds, reptiles and snakes, which exist nowhere else in the world. Almost all of them bore the unmistakable stamp of the American continent. In the song of the mocking-thrush, in the sharp scream of the vultures, in the large candlestick-like opuntias I noticed distinctly the vicinity of America; and yet these islands were separated from the continent by many miles and were very different in their geological constitution and their climate. Even more surprising was the fact that most of the inhabitants of each of the individual islands of the small archipelago were specifically different although closely related. I often asked myself how these strange animals and men had come into being. The simplest way seemed to be that the inhabitants of the various islands were descended from one another and had undergone modifications in the course of their descent, and that all inhabitants of the archipelago were descendants of those of the nearest continent, namely, America, where the colonization naturally would have its origin. But it was for a long time an unexplainable problem to me how the necessary modification could have been obtained.
The answer to this question is contained in the naturalistic conception of the evolution of the living organism. As the physicist subjects a substance to different conditions in order to study its properties, so Darwin, after his return, observed the phenomena that resulted in living beings under different circumstances. He made experiments in breeding pigeons, chickens, dogs, rabbits and plants. Through these experiments it was shown that the living forms continuously change in the course of their propagation. Under certain circumstances some living organisms change so much after a few generations that in comparing the newly bred forms with their ancestors, one could speak of two completely different species, each of which follows its own design of organization. Such a variability of forms is used by the breeder in order to develop organisms through cultivation that answer certain demands. A breeder can produce a species of sheep with an especially fine wool if he allows only those specimens of his flock to be propagated that have the finest wool. The quality of the wool is then improved in the course of the generations. After some time, a species of sheep is obtained which, in the formation of its wool, has progressed far beyond its ancestors. The same is true with other qualities of living organisms. Two conclusions can be drawn from this fact. The first is that nature has the tendency to change living beings; the second, that a quality that has begun to change in a certain direction increases in that direction, if in the process of propagation of organic beings those specimens that do not have this quality are excluded. The organic forms then assume other qualities in the course of time, and continue in the direction of their change once this process has begun. They change and transmit the changed qualities to their descendants.
The natural conclusion from this observation is that change and hereditary transmission are two driving principles in the evolution of organic beings. If it is to be assumed that in the natural course of events in the world, formations that are adapted to life come into being side by side with those not adapted as well as others, it must also be supposed that the struggle for life takes place in the most diversified forms. This struggle effects, without a plan, what the breeder does with the aid of a preconceived plan. As the breeder excludes the specimen from the process of propagation that would introduce undesired qualities into the development, so the struggle for life eliminates the unfit. Only the fit survive in evolution. The tendency for perpetual perfection enters thus into the evolutionary process like a mechanical law. After Darwin had seen this and after he had thereby laid a firm foundation to a naturalistic world conception, he could write the enthusiastic words at the end of his work, The Origin of Species, which introduced a new epoch of thought:
Thus, from the war of nature, from famine and death the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been and are being evolved.
At the same time one can see from this sentence that Darwin does not derive his conception from any anti-religious sentiment but merely from the conclusions that for him follow from distinctly significant facts. It was not hostility against the needs of religious experience that persuaded him to a rational view of nature, for he tells us distinctly in his book how this newly acquired world of ideas appeals to his heart.
Authors of the highest eminence seem to be fully satisfied with the view that each species has been independently created. To my mind it accords better with what we know of the laws impressed in matter by the Creator that the production and extinction of the past and present inhabitants of the world should have been due to secondary causes, like those determining the birth and death of the individual. When I view all beings not as special creations, but as the linear descendants of some few beings which lived long before the first bed of the Cambrian system was deposited, they seem to me to become ennobled. . . . Hence, we may look with some confidence to a secure future of great length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress toward perfection.
Darwin showed in great detail how the organisms grow and spread, how, in the course of their development, they transmit their properties once they are acquired, how new organs are produced and change through use or through lack of use, how in this way the organic beings are adjusted to their conditions of existence and how finally through the struggle for life a natural selection takes place by means of which an ever increasing variety of more and more perfect forms come into being.
In this way an explanation of teleologically adjusted beings seems to be found that requires no other method for organic nature than that which is used in inorganic nature. As long as it was impossible to offer an explanation of this kind it had to be admitted, if one wanted to be consistent, that everywhere in nature where a purpose-adjusted being came into existence, the intervention of an extraneous power had to be assumed. In every such case one had to admit a miracle.
Those who for decades before the appearance of Darwin's work had endeavored to find a naturalistic world and life conception now felt most vividly that a new direction of thought had been given. This feeling is expressed by David Friedrich Strauss in his book, The Old and the New Faith (1872).
One sees this is the way it must go; this is where the new banner is waving sprightly in the wind. It is a real joy in the sense of the loftiest joys of intellectual advance. We philosophers and critical theologians talked and talked to discredit the idea of a miracle. Our decree had no effect whatever, because we did not know how to demonstrate this idea as a superfluous one, because we did not know how to avoid it for we did not know of any energy of nature with which we could replace it where it seemed to be most necessary to be assumed. Darwin has demonstrated this energy of nature, this procedure of nature; he has opened the door through which a fortunate posterity will throw out the miracle once and for all times. Everyone who knows how much depends on miracles will praise him for that deed as one of the greatest benefactors of the human race.
Through Darwin's idea of fitness it is possible to think the concept of evolution really in the form of a natural law. The old doctrine of involution, which assumes that everything that comes into existence has been there in a hidden form before (compare pages in Part 1 Chapter IX), had been deprived of its last hope with this step. In the process of evolution as conceived by Darwin, the more perfect form is in no way contained in the less perfect one, for the perfection of a higher being comes into existence through processes that have nothing whatsoever to do with the ancestors of this being. Let us assume that a certain evolutionary series has arrived at the marsupials. The form of the marsupials contains nothing at all of a higher, more perfect form. It contains only the ability to change at random in the course of its propagation. Certain circumstances then come to pass that are independent of any “inner” latent tendency of development of the form of the marsupials but that are such that of all possible variations (mutations) the pro-simians survive. The forms of the marsupials contained that of the pro-simians no more than the direction of a rolling billiard ball contains the path it will take after it has been deflected from its original course by a second billiard ball.
Those accustomed to an idealistic mode of thinking had no easy time in comprehending this reformed conception of evolution. Friedrich Theodor Vischer, a man of extraordinary acumen and subtlety of spirit who had come from Hegel's school, writes as late as 1874 in an essay:
Evolution is an unfolding from a germ that proceeds from attempt to attempt until the picture that the germ contained latently as a possibility has become real. But once this is accomplished it stops and holds on to the form that is found, keeping it as a permanent one. Every concept as such would lose its firm outline if we were to consider the types that have existed on our planet for so many thousands of years as forever variable and above all if we were so to consider our own human type. We should then be unable any longer to trust our thoughts, the laws conceived by our thinking, our feelings, the pictures of our imagination, all of which are nothing but the clarifying imitations of forms of nature as it is known to us. Everything becomes questionable.
In another passage in the same essay he says:
I still find it a little hard, for instance, to believe that we should owe our eye to the process of seeing, our ear to that of hearing. The extraordinary weight that is given to the process of natural selection is something I am not quite satisfied with.
If Vischer had been asked whether or not he imagined that hydrogen and oxygen contained within themselves in a latent form a picture of water to make it possible for the latter to develop from the former, he would undoubtedly have answered, “No, neither in oxygen nor in hydrogen is there anything contained of the water that is formed; the conditions for the formation of this substance are given only when hydrogen and oxygen are combined under certain circumstances.” Is the situation then necessarily different when, through the two factors of the marsupials and the external conditions, the pro-simians came into being? Why should the pro-simians be contained as a possibility, as a scheme, in the marsupials in order to be capable of being developed from them? What comes into being through evolution is generated as a new formation without having been in existence in any previous form.
Thoughtful naturalists felt the weight of the new teleological doctrine no less than Strauss. Hermann Helmholtz belongs, without doubt, among those who, in the eighteen-fifties and sixties, could be considered as representatives of such thoughtful naturalists. He stresses the fact that the wonderful purpose-conformity in the structure of living organisms, which becomes increasingly apparent as science progresses, challenges the comparison of all life processes to human actions. For human actions are the only series of phenomena that have a character that is similar to the organic ones. The fitness of the arrangements in the world of organisms does, according to our judgment, in most cases indeed far surpass what human intelligence is capable of creating. It therefore cannot surprise us that it has occurred to people to seek the origin of the structure and function of the world of living beings in an intelligence far superior to that of man. Helmholtz says:
Before Darwin one could admit two kinds of explanations for the fact of organic purpose adjustment, both of which depended on an interference of a free intelligence in the course of natural phenomena. One either considered, according to the vitalistic theory, the life-processes as perpetually guided by a life-soul; or one saw in each species an act of a supernatural intelligence through which it was supposed to have been generated. . . . Darwin's theory contains an essentially new creative thought. It shows that a purpose-adjustment of the form in the organisms can come to pass also without interference of an intelligence through the random effect of a natural law. This is the law of the transmission of individual peculiarities from the parents to the descendants, a law that was long known and recognized but was merely in need of a definite demarcation.
Helmholtz now is of the opinion that such a demarcation is given by the principle of natural selection in the struggle for existence. A scientist who, like Helmholtz, belongs to the most cautious naturalists of that time, J. Henle, said in a lecture, “If the experiences of artificial breeding were to be applied to the hypothesis of Oken and Lamarck, it would have to be shown how nature proceeds in order to supply the mechanism through which the experimental breeder obtains his result. This is the task Darwin set for himself and that he pursued with admirable industry and acumen.”
The materialists were the ones who felt the greatest enthusiasm of all from Darwin's accomplishment. They had long been convinced that sooner or later a man like him would have to come along who would throw a philosophical light on the vast field of accumulated facts that was so much in need of a leading thought. In their opinion, the world conception for which they had fought could not fail after Darwin's discovery. Darwin approached his task as a naturalist. At first he moved within the limits reserved to the natural scientist. That his thoughts were capable of throwing a light on the fundamental problems of world conception, on the question of man's relation to nature, was merely touched upon in his book:
In the future I see open fields for far more important researches. Psychology will be securely based on the foundation . . ., of the necessary acquirement of each mental power and capacity by gradation. Much light will be thrown on the origin of man and his history.
For the materialists, this question of the origin of man became, in the words of Buechner, a matter of most intimate concern. In lectures he gave in Offenbach during the winter of 1866–67, he says:
Must the theory of transformation also be applied to our own race? Must it be extended to man, to us? Shall we have to submit to an application of the same principles or rules that have caused the life of all other organisms for the explanation of our own genesis and origin? Or are we — the lords of creation — an exception?
Natural science clearly taught that man could not be an exception. On the basis of exact anatomical investigations the English physiologist, T. H. Huxley, wrote in his book, Man's Place in Nature (1863):
The critical comparison of all organs and their modification in the series of the monkeys leads us to one and the same result, that the anatomical differences that separate man from the gorilla and the chimpanzee are not as great as the differences that separate the anthropoid apes from the lower species of monkeys.
Could there still be a doubt in the face of such facts that natural evolution had also produced man — the same evolution that had caused the series of organic beings as far as the monkey through growth, propagation, inheritance, transmutation of forms and the struggle for life?
During the course of the century this fundamental view penetrated more and more into the mainstream of natural science. Goethe, to be sure, had in his own way been convinced of this, and because of this conviction he had most energetically set out to correct the opinion of his contemporaries, which held that man lacked an intermaxillary bone in his upper jaw. All animals were supposed to have this bone; only man, so one thought, did not have it. In its absence one saw the proof that man was anatomically different from the animals, that the plan of his structure was to be thought along different lines. The naturalistic mode of Goethe's thinking inspired him to undertake elaborate anatomical studies to abolish this error. When he had achieved this goal he wrote in a letter to Herder, convinced that he had made a most important contribution to the knowledge of nature; “I compared the skulls of men and animals and I found the trail, and behold, there it is. Now I ask you not to tell, for it must be treated as a secret. But I want you to enjoy it with me, for it is like the finishing stone in the structure of man; now it is complete and nothing is lacking. Just see how it is!”
Under the influence of such conceptions the great question of philosophy of man's relation to himself and to the external world led to the task of showing by the method of natural science what actual process had led to the formation of man in the course of evolution. Thereby the viewpoint from which one attempted to explain the phenomena of nature changed. As long as one saw in every organism including man the realization of a purposeful design of structure, one had to consider this purpose also in the explanation of organic beings. One had to consider that in the embryo the later organism is potentially indicated. When this view was extended to the whole universe, it meant that an explanation of nature fulfilled its task best if it showed how the later stages of evolution with man as the climax are prepared in the earlier stages.
The modern idea of evolution rejected all attempts of science to recognize the potential later phases in the earlier stages. Accordingly, the later phase was in no way contained in the earlier one. Instead, what was gradually developed was the tendency to search in the later phases for traces of the earlier ones. This principle represented one of the laws of inheritance. One can actually speak of a reversal of the tendency of explanation. This reversal became important for ontogenesis, that is, for the formation of the ideas concerning the evolution of the individual being from the egg to maturity. Instead of showing the predisposition of the later organs in the embryo, one set out to compare the various stages that an organism goes through in the course of its individual evolution from the egg to maturity with those of other forms of organisms. Lorenz Oken was already moving in this direction. In the fourth volume of his General History of Nature for All Classes of Readers he wrote:
Years ago, through my physiological investigations, I arrived at the view that the developmental stages of the chicken in the egg have much similarity with different classes of animals. In the beginning it shows only the organs of infusoria, thereupon gradually assuming those of the polyps, jellyfish, shellfish, snails and so forth. Conversely, then, I also had to consider the classes of animals as evolutionary stages that proceeded parallel to the developmental stages of the chicken. This view of nature challenged me to the most minute observation of those organs that are added as new forms to every higher class of animal, as well as of the ones that are developed one after the other during the developmental process. It is, of course, not easy to establish a complete parallelism with such a difficult object as a chick egg because its development is so incompletely known. But to prove that the parallelism actually exists is indeed not difficult. It is most distinctly shown in the transformation of the insects, which is nothing more than the development of the young going on before our eyes outside the egg, and actually in so slow a tempo that we can observe and investigate every embryonic stage at our leisure.
Oken compares the stages of transformation of the insects with the other animals and finds that the caterpillars have a great similarity with worms, and the cocoons with crustaceous animals. From such similarities this ingenious thinker draws the conclusion that “there is, therefore, no doubt that we are here confronted with a conspicuous similarity that justifies the idea that the evolutionary history in the egg is nothing but a repetition of the history of the creation of the animal classes.” It came as a natural gift to this brilliant man to apprehend a great idea for which he did not even need the evidence of supporting facts. But it also lies in the nature of such subtle ideas that they have no great effect on those who work in the field of science. Oken appears like a comet on the firmament of German philosophy. His thought supplies a flood of light. From a rich treasure of ideas he suggests leading concepts for the most divergent facts. His method of formulating factual connections, however, was somewhat forced. He was too much preoccupied with the point he wanted to make. This attitude also prevailed in his treatment of the law of the repetition of certain animal forms in the ontogeny of others mentioned above.
In contrast to Oken, Karl Ernst von Baer kept to the facts as firmly as possible when he spoke, in his History of the Evolution of Animals (1828), of the observations that had led Oken to his idea:
The embryos of the mammals, birds, lizards and snakes, and probably also those of the turtles, in their earlier stages are extraordinarily similar to one another in their whole formation as well as in their individual parts. These embryos are so similar in fact that they can often only be distinguished by their sizes. I have in my possession two little embryos in alcohol that I forgot to label, and now I cannot possibly determine to what class they belong. They could be lizards, little birds or young mammals, so similar is the head and trunk formation of these animals. The extremities are still completely absent in these embryos and, even if they were there, at the first stages of their development they would not tell us anything because the feet of lizards and mammals, the wings and feet of birds, as well as the hands and feet of men, all develop from the same original form.
Such facts of embryological development excited the greatest interest of those thinkers who tended toward Darwinism. Darwin had proven the possibility of change in organic forms and, through transformation, the species now in existence might possibly be descended from a few original forms, or perhaps only one. Now it was shown that in their first phases of development the various living organisms are so similar to each other that they can scarcely be distinguished from one another, if at all. These two ideas, the facts of comparative embryology and the idea of descent, were organically combined in 1864 by Fritz Müller (1821–97) in his thoughtful essay, Facts and Arguments for Darwin. Müller is one of those high-minded personalities who needs a naturalistic world conception because they cannot breathe spiritually without it. Also, in regard to his own action, he would feel satisfaction only when he could feel that his motivation was as necessary as a force of nature. In 1852 Müller settled in Brazil. For twelve years he was a teacher at the gymnasium in Desterro on the island of Santa Catharina, not far from the coast of Brazil. In 1867 he had to give up this position. The man of the new world conception had to give way to the reaction that, under the influence of the Jesuits, took hold of his school. Ernst Haeckel has described the life and activity of Fritz Müller in the Jenaische Zeitschrift fur Naturwissenschaft (Vol. XXXI N.F. XXIV 1897).
Darwin called Müller the “prince of observers,” and the small but significant booklet, Facts and Arguments for Darwin, is the result of a wealth of observations. It deals with a particular group of organic forms, the crustaceans, which are radically different from one another in their maturity but are perfectly similar at the time when they leave the egg. If one presupposes, in the sense of Darwin's theory of descent, that all crustacean forms have developed from one original type, and if one accepts the similarity in the early stages as an inherited element of the form of their common ancestor, one has thereby combined the ideas of Darwin with those of Oken pertaining to the repetition of the history of the creation of the animal species in the evolution of the individual animal form. This combination was accomplished by Fritz Müller. He thereby brought the earlier forms of an animal class into a certain law-determined connection with the later ones, which, through transformation, have formed out of them. The fact that at an earlier stage the ancestral form of a being now living has had a particular form caused its descendants at a later time to have another particular form. By studying the stages of the development of an organism one becomes acquainted with its ancestors whose nature has caused the characteristics of the embryonic forms. Phylogenesis and ontogenesis are, in Fritz Müller's book, connected as cause and effect. With this step a new element had entered the Darwinian trend of ideas. This fact retains its significance even though Müller's investigations of the crustaceans were modified by the later research of Arnold Lang.
Only four years had passed since the appearance of Darwin's Origin of the Species when Müller's book was published as its defense and confirmation. Müller had shown how, with one special class of animals, one should work in the spirit of the new ideas. Then, in 1866, seven years after the Origin of the Species, a book appeared that completely absorbed this new spirit. Using the ideas of Darwinism on a high level of scientific discussion, it threw a great deal of light on the problems of the interconnection of all life phenomena. This book was Ernst Haeckel's General Morphology of Organisms. Every page reflected his attempt to arrive at a comprehensive synopsis of the totality of the phenomena of nature with the help of new thoughts. Inspired by Darwinism, Haeckel was in search of a world conception.
Haeckel did his best in two ways to attempt a new world conception. First, he continually contributed to the accumulation of facts that throw light on the connection of the entities and energies of nature. Second, with unbending consistency he derived from these facts the ideas that were to satisfy the human need for explanation. He held the unshakable conviction that from these facts and ideas man can arrive at a fully satisfactory world explanation. Like Goethe, Haeckel was convinced in his own way that nature proceeds in its work “according to eternal, necessary and thereby divine laws, so that not even the deity could change it.” Because this was clear to him, he worshipped his deity in these eternal and necessary laws of nature and in the substances in which they worked. As the harmony of the natural laws, which are with necessity interconnected, satisfies reason, according to his view, so it also offers to the feeling heart, or to the soul that is ethically or religiously attuned, whatever it may thirst for. In the stone that falls to the ground attracted by gravity there is a manifestation of the same divine order that is expressed in the blossom of a plant and in the human spirit that created the drama of Wilhelm Tell.
How erroneous is the belief that the feeling for the wonderful beauty of nature is destroyed by the penetration of reason into laws of nature is vividly demonstrated in the work of Ernst Haeckel. A rational explanation of nature had been declared to be incapable of satisfying the needs of the soul. Wherever man is disturbed in his inner life through knowledge of nature, it is not the fault of knowledge but of man himself. His sentiments are developed in a wrong direction. As we follow a naturalist like Haeckel without prejudice on his path as an observer of nature, we feel our hearts beat faster. The anatomical analysis, the microscopic investigation does not detract from natural beauty but reveals a great deal more of it. There is no doubt that there is an antagonism between reason and imagination, between reflection and intuition, in our time. The brilliant essayist, Ellen Key, is without doubt right in considering this antagonism as one of the most important phenomena of our time (compare Ellen Key, Essays, S. Fischer Verlag, Berlin, 1899). Whoever, like Ernst Haeckel, digs deep into the treasure mine of facts, boldly emerges with the thoughts resulting from these facts and climbs to the heights of human knowledge, can see in the explanation of nature only an act of reconciliation between the two contesting forces of reflection and intuition that “alternate in forcing each other into submission” (Ellen Key). Almost simultaneously with the publication of the book in which Haeckel presented with unflinching intellectual honesty his world conception derived from natural science, that is, with the appearance of his Riddles of the Universe in 1899, he began a serial publication called Artforms of Nature. In it he gives pictures of the inexhaustible wealth of wonderful formations that nature produces and that surpass “by far all artistic forms created by man” in beauty and in variety. The same man who introduces our mind to the law-determined order of nature leads our imagination to the beauty of nature.
The need to bring the great problems of world conception into direct contact with scientific, specialized research led Haeckel to one of the facts concerning which Goethe said that they represent the significant points at which nature yields the fundamental ideas for its explanation of its own accord, meeting us halfway in our search. This was realized by Haeckel as he investigated how Oken's thesis, which Fritz Müller had applied to the crustaceans, could be fruitfully applied to the whole animal kingdom. In all animals except the Protista, which are one-celled organisms, a cup- or jug-shaped body, the gastrula, develops from the zygote with which the organism begins its ontogenesis. This gastrula is an animal form that is to be found in the first stages of development of all animals from the sponges to man. It consists merely of skin, mouth and stomach. There is a low class of zoophytes that possess only these organs during their lives and therefore resemble gastrulae. This fact is interpreted by Haeckel from the point of view of the theory of descent. The gastrula form is an inherited form that the animal owes to the form of its common ancestor. There had been, probably millions of years before, a species of animals, the gastrae, that was built in a way similar to that of the lower zoophytes still living today — the sponges, polyps, etc. From this animal species all the various forms living today, from the polyps, sponges, etc., to man, repeat this original form in the course of their ontogenies.
In this way an idea of gigantic scope had been obtained. The path leading from the simple to the complicated, to the perfect form in the world of organisms, was thereby indicated in its tentative outline. A simple animal form develops under certain circumstances. One or several individuals of this form change to another form according to the conditions of life to which they are exposed. What has come into existence through this transmutation is again transmitted to descendants. There are then two different forms, the old one that has retained the form of the first stage, and a new one. Both of these forms can develop in different directions and into different degrees of perfection. After long periods of time an abundant wealth of species comes into existence through the transmission of the earlier form and through new formations by means of the process of adaptation to the conditions of life.
In this manner Haeckel connects today's processes in the world of organisms with the events of primeval times. If we want to explain some organ of an animal of the present age, we look back to the ancestors that had developed this organ under the circumstances in which they lived. What has come into existence through natural causes in earlier times has been handed down to our time through the process of heredity. Through the history of the species the evolution of the individual receives its explanation. The phylogenesis, therefore, contains the causes for the ontogenesis. Haeckel expresses this fact in his fundamental law of biogenetics: “The short ontogenesis or development of the individual is a rapid and brief repetition, an abbreviated recapitulation of the long process of phylogenesis, the development of the species.”
Through this law every attempt at explanation through special purposes, all teleology in the old sense, has been eliminated. One no longer looks for the purpose of an organ; one looks for the causes through which it has developed. A given form does not point to a goal toward which it strives, but toward the origin from which it sprang. The method of explanation for the organic phenomena has become the same as that for the inorganic. Water is not considered the aim of oxygen, nor is man considered the purpose of creation. Scientific research is directed toward the origin of, and the actual cause for, living beings. The dualistic mode of conception, which declares that the organic and the inorganic has to be explained according to two different principles, gives way to a monistic mode of conception, to a monism that has only one uniform mode of explanation for the whole of nature.
Haeckel characteristically points out that through his discovery the method has been found through which every dualism in the above-mentioned sense must be overcome.
Phylogenesis is the mechanical cause of ontogenesis. With this statement our basically monistic conception of organic evolution is clearly characterized, and on the truth of this principle depends primarily the truth of the gastraea theory. . . . Every naturalist, who in the field of biogenesis is not satisfied with a mere admiration of strange phenomena but strives for an understanding of their significance, will, in the future, either have to side with or against this principle. It marks at the same time the complete break that separates the older teleological and dualistic morphology from the new mechanical and monistic one. If the physiological functions of inheritance and adaptation have been proven to be the only causes of the process of organic formation, then every kind of teleology, of dualistic and metaphysical mode of conception has thereby been eliminated from the field of biogenesis; the sharp contrast between the leading principles is clearly marked. Either a direct and causal connection between ontogeny and phylogeny exists or it does not. There is no third possibility! Either epigenesis and descent, or pre-formation and creation! (Compare alsoin Part 1 Chapter IX of this book.)
After Haeckel had absorbed Darwin's view of the origin of man he defended forcefully the conclusion that must be drawn from it. It was impossible for him just to hint hesitatingly, like Darwin, at this “problem of all problems.” Anatomically and physiologically man is not distinguishable from the higher animals. Therefore, the same origin must be attributed to him as to them. Haeckel boldly defended this opinion and the consequences that followed from it for the conception of the world. There was no doubt for him that in the future the highest manifestations of man's life, the activities of his spirit, were to be considered under the same viewpoint as the function of the simplest living organism. The observation of the lowest animals, the protozoa, infusoria, rhizopods, taught him that these organisms had a soul. In their motions, in the indications of the sensations they show, he recognized manifestations of life that only had to be increased and perfected in order to develop into man's complicated actions of reason and will.
Beginning with the gastraea, which lived millions of years ago, what steps does nature take to arrive at man? This was the comprehensive question as stated by Haeckel. He supplied the answer in his Anthropogenesis, which appeared in 1874. In its first part, this book deals with the history of the individual (ontogenesis), in the second part, with that of the species (phylogenesis). He showed point by point how the latter contains the causes of the former. Man's position in nature had thereby been determined according to the principles of the theory of descent. To works like Haeckel's Anthropogenesis, the statement that the great anatomist, Karl Gegenbaur, made in his Comparative Anatomy (1870) can be justly applied. He wrote that in exchange for the method of investigation Darwin gave to science with his theory he received in return clarity and firmness of purpose. In Haeckel's view, the method of Darwinism had also supplied science with the theory of the origin of man.
What actually was accomplished by this step can be appreciated in its full measure only if one looks at the opposition with which Haeckel's comprehensive application of the principles of Darwinism was received by the followers of idealistic world conceptions. It is not even necessary to quote those who, blindly believing in the traditional opinion, turned against the “monkey theory,” or those who believed that all finer, higher morality would be endangered if men were no longer convinced that they had a “purer, higher origin.” Other thinkers, although quite open-minded with regard to new truths, found it difficult to accept this new truth. They asked themselves the question, “Do we not deny our own rational thinking if we no longer look for its origin in a general world reason over us, but in the animal kingdom below?” Mentalities of this sort eagerly attacked the points where Haeckel's view seemed to be without support of the facts. They had powerful allies in a number of natural scientists who, through a strange bias, used their factual knowledge to emphasize the points where actual experience was still insufficient to prove the conclusions drawn by Haeckel. The typical, and at the same time the most impressive, representative of this viewpoint of the naturalists was Rudolf Virchow (1821–1902). The opposition of Virchow and Haeckel can be characterized as follows. Haeckel puts his trust in the inner consistency of nature, concerning which Goethe is of the opinion that it is sufficient to make up for man's inconsistency. Haeckel, therefore, argues that if a principle of nature has been verified for certain cases, and if we still lack the experience to show its validity in other cases, we have no reason to hold the progress of our knowledge back. What experience denies us today, it may yield tomorrow. Virchow is of the opposite opinion. He wants to yield as little ground as possible to a comprehensive principle. He seems to believe that life for such a principle cannot be made hard enough. The antagonism between these two spirits was brought to a sharp point at the Fiftieth Congress of German naturalists and doctors in 1877. Haeckel read a paper there on the topic, The Theory of Evolution of Today in Its Relation to Science in General.
In 1894 Virchow felt that he had to state his view in the following way. “Through speculation one has arrived at the monkey theory; one could just as well have ended up with an elephant theory or a sheep theory.” What Virchow demanded was incontestable proof of this theory. As soon as something turned up that fitted as a link in the chain of the argumentation, Virchow attempted to invalidate it with all means at his disposal.
Such a link in the chain of proof was presented with the bone remnants that Eugen Dubois had found in Java in 1894. They consisted of a skull and thigh bone and several teeth. Concerning this find, an interesting discussion arose at the Congress of Zoologists at Leyden. Of twelve zoologists, three were of the opinion that these bones came from a monkey and three thought they came from a human being; six, however, believed they presented a transitional form between man and monkey. Dubois shows in a convincing manner in what relation the being whose bone remnants were under discussion stood to the present monkey, on the one hand, and to man of today, on the other. The theory of evolution of natural science must claim such intermediary forms. They fill the holes that exist between numerous forms of organisms. Every new intermediary form constitutes a new proof for the kinship of all living organisms. Virchow objected to the view that these bone remnants came from such an intermediary form. At first, he declared that it was the skull of a monkey and the thigh bone of a man. Expert paleontologists, however, firmly pronounced, according to the careful report, on the finding, that the remnants belonged together. Virchow attempted to support his view that the thigh bone could be only that of a human being with the statement that a certain growth in the bone proved that it must have had a disease that could only have been healed through careful human attention. The paleontologist, Marsch, [e.Ed: perhaps American paleontologist, Othniel Charles Marsh (1831–1899)] however, maintained that similar bone extuberances occurred in wild animals as well. A further statement of Virchow's, that the deep incision between the upper rim of the eye socket and the lower skull cover of the alleged intermediary form proved it to be the skull of a monkey was then contradicted by the naturalist Nehring, who claimed that the same formation was found in a human skull from Santos, Brazil. Virchow's objections came from the same turn of mind that also caused him to consider the famous skulls of Neanderthal, Spy, etc., as pathological formations, while Haeckel's followers regarded them as intermediary forms between monkey and man.
Haeckel did not allow any objections to deprive him of his confidence in his mode of conception. He continued his scientific work without swerving from the viewpoints at which he had arrived, and through popular presentations of his conception of nature, he influenced the public consciousness. In his book, Systematic Phylogenesis, Outline of a Natural System of Organisms on the Basis of the History of Species (1894–96), he attempted to demonstrate the natural kinship of organisms in a strictly scientific method. In his Natural History of Creation, which, from 1868–1908, appeared in eleven editions, he gave a popular explanation of his views. In 1899, in his popular studies on monistic philosophy entitled, The Riddles of the Universe, he gave a survey of his ideas in natural philosophy by demonstrating without reserve the many applications of his basic thoughts. Between all these works he published studies on the most diverse specialized researches, always paying attention at the same time to the philosophical principles and the scientific knowledge of details.
The light that shines out from the monistic world conception is, according to Haeckel's conviction, to “disperse the heavy clouds of ignorance and superstition that have heretofore spread an impenetrable darkness over the most important one of all problems of human knowledge, that is, the problem concerning man's origin, his true nature and his position in nature.” This is what he said in a speech given August 26, 1898 at the Fourth International Congress of Zoologists in Cambridge, On Our Present Knowledge Concerning the Origin of Man. In what respect his world conception forms a bond between religion and science, Haeckel has shown in an impressive way in his book, Monism as a Bond between Religion and Science, Credo of a Naturalist, which appeared in 1892.
If one compares Haeckel with Hegel, one can see distinctly the difference in the tendencies of world conception in the two halves of the nineteenth century. Hegel lives completely in the idea and accepts only as much as he needs from the world of facts for the illustration of his idealistic world picture. Haeckel is rooted with every fiber of his being in the world of facts, and he derives from this world only those ideas toward which these facts necessarily tend. Hegel always attempts to show that all beings tend to reach their climax of evolution in the human spirit; Haeckel continuously endeavors to prove that the most complicated human activities point back to the simplest origins of existence. Hegel explains nature from the spirit; Haeckel derives the spirit from nature. We can, therefore, speak of a reversal of the thought direction in the course of the century. Within German intellectual life, Strauss, Feuerbach and others began this process of reversal. In their materialism the new direction found a provisional extreme expression, and in Haeckel's thought world it found a strictly methodical-scientific one. For this is the significant thing in Haeckel, that all his activity as a research worker is permeated by a philosophical spirit. He does not at all work toward results that for some philosophical motivation or other are considered to be the aim of his world conception or of his philosophical thinking. What is philosophical about him is his method. For him, science itself has the character of a world conception. His very way of looking at things predestines him to be a monist. He looks upon spirit and nature with equal love. For this reason he could find spirit in the simplest organism. He goes even further than that. He looks for the traces of spirit in the inorganic particles of matter:
Every atom possesses an inherent quantity of energy and in this sense is animate. Without assuming a soul for the atom, the simplest and most general phenomena of chemistry are unexplainable. Pleasure and displeasure, desire and aversion, attraction and repulsion must be a common property of all material atoms. For the motion of the atoms, which must take place in the formation and dissolution of every chemical compound can only be explained if we assume that they have sensation and will. On this assumption the generally accepted chemical doctrine of affinity is really based.
As he traces spirit down to the atom so he follows the purely material mechanism of events up to the most lofty accomplishments of the spirit:
The spirit and soul of man are also nothing else but energies that are inseparably bound to the material substratum of our bodies. As the motion of our flesh is bound to the form elements of our muscles, so our mind's power of thinking is bound to the form elements of our brains. Our spiritual energies are simply functions of these physical organs just as every energy is a function of a material body.
One must not confuse this mode of conception with one that dreams souls in a hazy mystical fashion into the entities of nature and then assumes that they are more or less similar to that of man. Haeckel is a strict opponent of a world conception that projects qualities and activities of man into the external world. He has repeatedly expressed his condemnation of the humanization of nature, of anthropomorphism, with a clarity that cannot be misunderstood. If he attributes animation to inorganic matter, or to the simplest organisms, he means by that nothing more than the sum of energy manifestations that we observe in them. He holds strictly to the facts. Sensation and will are for him no mystical soul energies but are nothing more than what we observe as attraction and repulsion. He does not mean to say that attraction and repulsion are really sensation and will. What he means is that attraction and repulsion are on the lowest stage what sensation and will are on a higher one. For evolution is for him not merely an unwrapping of the higher stages of the spiritual out of the lower forms in which they are already contained in a hidden fashion, but a real ascent to new formations, an intensification of attraction and repulsion into sensation and will (compare prior comments in this Chapter).
This fundamental view of Haeckel agrees in a certain way with that of Goethe. He states in this connection that he had arrived at the fulfillment of his view of nature with his insight into the “two great springs of all nature,” namely, polarity and intensification (Polarität und Steigerung), polarity “belonging to matter insofar as we think of it materially, intensification insofar as we think of it spiritually. The former is engaged in the everlasting process of attraction and repulsion, the latter in a continual intensification. As matter can never be and act without spirit, however, nor spirit without matter, so matter can also be intensified and the spirit will never be without attraction and repulsion.”
A thinker who believes in such a world conception is satisfied to explain by other such things and processes, the things and processes that are actually in the world. The idealistic world conceptions need, for the derivation of a thing or process, entities that cannot be found within the realm of the factual. Haeckel derives the form of the gastrula that occurs in the course of animal evolution from an organism that he assumes really existed at some time. An idealist would look for ideal forces under the influence of which the developing germ becomes the gastrula. Haeckel's monism draws everything he needs for the explanation of the real world from the same real world. He looks around in the world of the real in order to recognize in which way the things and processes explain one another. His theories do not have the purpose for him, as do those of the idealist, to find a higher element in addition to the factual elements, but they merely serve to make the connection of the facts understandable. Fichte, the idealist, asked the question of man's destination. He meant by that something that cannot be completely presented in the form of the real, the factual; something that reason has to produce as an addition to the factually given existence, an element that is to make the real existence of man translucent by showing it in a higher light. Haeckel, the monistic contemplator of the world, asks for the origin of man, and he means by that the factual origin, the lower organism out of which man had developed through actual processes.
It is characteristic that Haeckel argues for the animation of the lower organisms. An idealist would have resorted to rational conclusions. He would present necessities of thought. Haeckel refers to what he has seen.
Every naturalist, who, like me, has observed for many years the life activities of the one-celled protozoa, is positively convinced that they, too, possess a soul. This cellular soul consists also of a sum of sensations, perceptions and will activities; sensation, thinking and will of our human souls differ from those of the cellular soul only in degree.
The idealist attributes spirit to matter because he cannot accept the thought that spirit can develop from mere matter. He believes that one would have to deny the spirit if one does not assume it to exist before its appearance in forms of existence without organs, without brains. For the monist, such thoughts are not possible. He does not speak of an existence that is not manifested externally as such. He does not attribute two kinds of properties to things: those that are real and manifested in them and those that in a hidden way are latent in them only to be revealed at a higher stage of development. For him, there is what he observes, nothing else, and if the object of observation continues its evolution and reaches a higher stage in the course of its development, then these later forms are there only in the moment when they become visible.
How easily Haeckel's monism can be misunderstood in this direction is shown by the objections that were made by the brilliant thinker, Bartholomaeus von Carneri (1821–1909), who made lasting contributions for the construction of an ethics of this world conception. In his book, Sensations and Consciousness, Doubts Concerning Monism (1893), he remarks that the principle, “No spirit without matter, but also no matter without spirit,” would justify our extending this question to the plant and even to the next rock we may stumble against, and to attribute spirit also to them. Without doubt such a conclusion would lead to a confusion of distinctions. It should not be overlooked that consciousness arises only through the cell activity in the cerebrum. “The conviction that there is no spirit without matter, that is to say, that all spiritual activity is bound to a material activity, the former terminating with the latter, is based on experience, while there is no experience for the statement that there is always spirit connected with matter.” Somebody who would want to attribute animation to matter that does not show any trace of spirit would be like one who attributed the function to indicate time not to the mechanism of a watch but to the metal out of which it is made.
Properly understood, Haeckel's view is not touched by Carneri's criticism. It is safe from this criticism because Haeckel holds himself strictly within the bounds of observation. In his Riddles of the Universe, he says, “I, myself, have never defended the theory of atom-consciousness. I have, on the contrary, expressly emphasized that I think the elementary psychic activities of sensation and will, which are attributed to the atoms, as unconscious.” What Haeckel wants is only that one should not allow a break in the explanation of natural phenomena. He insists that one should trace back the complicated mechanism by which spirit appears in the brain, to the simple process of attraction and repulsion of matter.
Haeckel considers the discovery of the organs of thought by Paul Flechsig to be one of the most important accomplishments of modern times. Flechsig had pointed out that in the gray matter of the brain there are to be found the four seats of the central sense organs, or four “inner spheres of sensation,” the spheres of touch, smell, sight and hearing. “Between the sense centers lie thought centers, the ‘real organs of mental life.’ They are the highest organs of psychic activity that produce thought and consciousness. . . . These four thought centers, distinguished from the intermediate sense centers by a peculiar and highly elaborate nerve structure, are the true organs of thought, the only organs of our consciousness. Recently, Flechsig has proved that man has some especially complicated structures in some of these organs that cannot be found in the other mammals and that explain the superiority of human consciousness.” (Riddles of the Universe, Chapt. X.)
Passages like these show clearly enough that Haeckel does not intend to assume, like the idealistic philosophers, the spirit as implicitly contained in the lower stages of material existence in order to be able to find it again on the higher stages. What he wanted to do was to follow the simplest phenomena to the most complicated ones in his observation, in order to show how the activity of matter, which in the most primitive form is manifested in attraction and repulsion, is intensified in the higher mental operations.
Haeckel does not look for a general spiritual principle for lack of adequate general laws explaining the phenomena of nature and mind. So far as his need is concerned, his general law is indeed perfectly sufficient. The law that is manifested in the mental activities seems to him to be of the same kind as the one that is apparent in the attraction and repulsion of material particles. If he calls atoms animated, this has not the same meaning that it would have if a believer in an idealistic world conception did so. The latter would proceed from the spirit. He would take the conceptions derived from the contemplation of the spirit down into the simplest functions of the atoms when he thinks of them as animated. He would explain thereby the natural phenomena from entities that he had first projected into them. Haeckel proceeds from the contemplation of the simplest phenomena of nature and follows them up to the highest spiritual activities. This means that he explains the spiritual phenomena from laws that he has observed in the simplest natural phenomena.
Haeckel's world picture can take shape in a mind whose observation extends exclusively to natural processes and natural entities. A mind of this kind will want to understand the connection within the realm of these events and beings. His ideal would be to see what the processes and beings themselves reveal with respect to their development and interaction, and to reject rigorously everything that might be added in order to obtain an explanation of these processes and activities. For such an ideal one is to approach all nature as one would, for instance, proceed in explaining the mechanism of a watch. It is quite unnecessary to know anything about the watchmaker, about his skill and about his thoughts, if one gains an insight into the mechanical actions of its parts. In obtaining this insight one has, within certain limits, done everything that is admissible for the explanation of the operation of the watch. One ought to be clear about the fact that the watch itself cannot be explained if another method of explanation is admitted, as, for instance, if somebody thought of some special spiritual forces that move the hour and minute hands according to the course of the sun. Every suggestion of a special life force, or of a power that works toward a “purpose” within the organisms, appears to Haeckel as an invented force that is added to the natural processes. He is unwilling to think about the natural processes in any other way than by what they themselves disclose to observation. His thought structure is to be derived directly from nature.
In observing the evolution of world conception, this thought structure strikes us, as it were, as the counter-gift from the side of natural science to the Hegelian world conception, which accepts in its thought picture nothing from nature but wants everything to originate from the soul. If Hegel's world conception said that the self-conscious ego finds itself in the experience of pure thought, Haeckel's view of nature could reply that the thought experience is a result of the nature processes, is, indeed, their highest product. If the Hegelian world conception would not be satisfied with such a reply, Haeckel's naturalistic view could demand to be shown some inner thought experience that does not appear as if it were a mirror reflection of events outside thought life. In answer to this demand, a philosophy would have to show how thought can come to life in the soul and can really produce a world that is not merely the intellectual shadow of the external world. A thought that is merely thought, merely the product of thinking, cannot be used as an effective objection to Haeckel's view. In the comparison mentioned above, he would maintain that the watch contains nothing in itself that allows a conclusion as to the personality, etc., of the watchmaker. Haeckel's naturalistic view tends to show that, as long as one is merely confronted with nature, one cannot make any statement concerning nature except what it records. In this respect this naturalistic conception is significant as it appears in the course of the development of world conception. It proves that philosophy must create a field for itself that lies in the realm of spontaneous creativity of thought life beyond the thoughts that are gained from nature.
Philosophy must take the step beyond Hegel that was pointed out in a previous chapter. It cannot consist of a method that moves in the same field with natural science. Haeckel himself probably felt not the slightest need to pay any attention to such a step of philosophy. His world conception does bring thoughts to life in the soul, but only insofar as their life has been stimulated by the observation of natural processes. The world picture that thought can create when it comes to life in the soul without this stimulus represents the kind of higher world conception that would adequately complement Haeckel's picture of nature. One has to go beyond the facts that are directly contained in the watch if one wants to know, for instance, something about the form of the watchmaker's face. But, for this reason, one has no right to demand that Haeckel's naturalistic view itself should not speak as Haeckel does when he states what positive facts he has observed concerning natural processes and natural beings.