# Worldviews in the 19th Century

## GA 18a

### Darwinism and Worldview

If the idea of expediency were to undergo a reform in the sense of a natural worldview, then the expedient structures of animate nature would have to be explained in the same way that physicists and chemists explain inanimate processes. When a magnetic rod attracts iron filings, no physicist thinks that a force is at work in the rod that is working toward the goal, the purpose of attraction. When hydrogen and oxygen combine to form water, the chemist does not interpret this as if something were at work in the two materials with the purpose of forming water in mind. An explanation of living beings dominated by just such a natural disposition must say: organisms become purposeful without anything in nature aiming at this purposefulness. Purposefulness arises without being predisposed as such anywhere. Charles Darwin gave such an explanation of purposefulness. He took the position of recognizing that nothing in nature wants purposefulness. Nature does not consider whether what arises in it is purposeful or not. It therefore produces the non-purposeful and the purposeful indiscriminately. What is purposeful anyway? It is that which is arranged in such a way that its needs and living conditions correspond to the external circumstances of existence. On the other hand, that which is not the case is non-purposeful. What will happen if, given nature's complete lack of planning, all degrees of more or less purposefulness arise, from the most purposeful to the [most impractical]? Every being will seek to shape its existence in accordance with the given circumstances. The appropriate will succeed in this without further ado, while the more or less appropriate will succeed only to a limited degree. Now there is one more thing to consider: nature is not a thrifty hostess when it comes to the production of living beings. The number of germs is enormous. This overabundance in the production of germs is offset only by a limited amount of resources for life. The result will be that those beings that are more suitably equipped for acquiring food will have an easier time developing. If a suitably equipped being strives to preserve its existence alongside an unsuitably equipped being, the more suitable being will outrank the less suitable one. The latter must perish alongside the former. The capable, i.e., the purposeful, survives, while the incapable, i.e., the unpurposeful, does not survive. This is the “struggle for existence.” It causes the purposeful to survive, even if the unpurposeful arises indiscriminately alongside the purposeful in nature. Through a law that is as objective and as wisdomless as only a mathematical or mechanical law of nature can be, the course of natural development tends toward appropriateness, without this tendency being inherent in nature in any way.

Darwin was led to this idea by the work of the economist Malthus, “An Essay on the Principle of Population.” In it, he explains that there is constant competition within human society because the population is growing at a much faster rate than the amount of food available. Darwin generalized this law, which he established for human history, into a comprehensive law for the entire living world.

Darwin now had to show how this struggle for existence became the creator of the manifold forms of living beings, how it overturned Linnaeus's old principle that “there are as many species in the animal and plant kingdoms as there are different forms created in principle.” Darwin's doubts about this principle became clear to him during a trip to South America and Australia in the summer of 1831. He recounts how these doubts took hold in his mind: "When I visited the Galapagos Archipelago, which lies in the Pacific Ocean about five hundred English miles from the South American coast, during the voyage of the Beagle, I found myself surrounded by peculiar species of birds, reptiles, and snakes that exist nowhere else in the world. Yet almost all of them bore an American character. In the song of the mockingbird, in the sharp cry of the vulture, in the large, candelabra-like opuntias, I clearly noticed the proximity to America; and yet these islands were so many miles away from the mainland and differed greatly from it in their geological constitution and climate. Even more surprising was the fact that most of the inhabitants of each individual island in this small archipelago were specifically different, even though they were closely related to each other. [...] At the time, I often wondered how these peculiar animals and people had come into being. The simplest explanation seemed to be that the inhabitants of the various islands were descended from each other and had undergone modifications in the course of their descent, and that all the inhabitants of the archipelago were descended from those of the nearest mainland, namely America, from which colonization would naturally have originated. However, one problem remained inexplicable to me for a long time: how the necessary degree of modification could have been achieved. The answer to this question lies in the natural conception of the development of living beings. Just as a physicist subjects a substance to different conditions in order to learn about its properties, Darwin observed the phenomena that arise in living beings under different conditions after his return home. He conducted breeding experiments with pigeons, chickens, dogs, rabbits, and cultivated plants. These experiments showed how living forms undergo continuous change in the course of their reproduction. Under certain conditions, certain living beings change after a few generations in such a way that, if one compares the newly created forms with their ancestors, one could speak of two completely different species, each of which follows its own organizational plan. Breeders use this variability of forms to develop cultivated organisms that serve specific purposes. They can breed a type of sheep with particularly fine wool by allowing only those individuals in their flock with the finest wool to reproduce. From among the offspring, they again select the individuals with the finest wool. The fineness of the wool then increases over the generations. After some time, a breed of sheep is obtained that is very different from its ancestors in terms of wool formation. The same is true of other characteristics of living beings. Two things follow from this fact. First, that there is a tendency in nature to transform living beings; and second, that a characteristic that has begun to change in a certain direction will increase in that direction if, during the reproduction of living beings, those individuals that do not yet have this characteristic are excluded. Organic forms thus acquire different characteristics over time and continue in the direction of their transformation once it has begun. They transform and pass on transformed characteristics to their offspring.

The natural conclusion from this observation is that change and inheritance are two driving principles in the development of living beings. If we assume that, in a natural way, beings in the world change in such a way that the useful arises alongside the useless and the more or less useful, then we must also assume a struggle between the manifold changed forms. This struggle achieves haphazardly what the breeder achieves systematically. Just as the breeder excludes from reproduction those individuals that would bring into the development what he does not want, so the struggle for existence eliminates the unsuitable. Only what is suitable for development remains. This gives rise to a tendency toward constant improvement, like a mechanical law. After recognizing this and thus laying a secure foundation for a naturalistic worldview, Darwin was able to conclude his work On the Origin of Species, which ushered in a new era of thought, with the enthusiastic words: "From the struggle of nature, from hunger and death, springs the highest thing we can comprehend, the production of higher animals. There is something magnificent in this view of life, according to which, with all its various powers, it was originally created by the Creator from few forms, or perhaps only one; and that, while this planet moves in circles according to the definite laws of gravity, an endless number of the most beautiful and wonderful forms have been developed and are still being developed from a simple beginning." At the same time, it can be seen from this sentence that Darwin arrived at his view not through any anti-religious sentiments, but solely from the conclusions that arose for him from the clearly speaking facts. It was certainly not the case that hostility toward the needs of emotion led him to a purely rational view of nature, for he tells us clearly in his book how the world of ideas he had gained spoke to his heart: "Very eminent writers seem to be quite satisfied with the view that each of the species was created independently. In my opinion, it is more consistent with the laws, as far as we know, that the Creator has impressed upon matter, that the production and extinction of the former and present inhabitants of the earth, as well as the provisions for the birth and death of an individual, are dependent on secondary causes. If I regard all beings not as special creations, but as linear descendants of a few beings that lived long before the younger geological strata were deposited, they seem to me to be ennobled by this." “We can confidently look forward to a future of great length. And since natural selection works only through and for the good of every being, all physical and mental talents will strive for perfection.”

Darwin used a wealth of facts to show how organisms grow and reproduce, how they pass on characteristics acquired in the course of their development, how new organs arise and change through use or disuse, and how creatures adapt to their conditions of existence; and finally how the struggle for existence results in natural selection (selective breeding), giving rise to diverse and ever more perfect forms.

This provides an explanation of purposeful beings that makes it unnecessary to proceed differently in organic nature than in inorganic nature. As long as such an explanation could not be given, one had to admit, if one wanted to be consistent, that wherever something purposeful arises in nature, a power foreign to nature intervenes. This basically meant admitting a miracle in every such case.

Those who, for decades before the publication of Darwin's work, had strived for a natural view of the world and life, now felt most vividly that a new direction of thought had been given. David Friedrich Strauss expressed this feeling in 1872 in his “Old and New Faith” with the words: "One sees that we must go where the banners flutter merrily in the wind. Yes, merrily, in the sense of the purest, most sublime joy of the spirit. We philosophers and critical theologians have talked a good game when we decreed the miracle to be on its way out; our pronouncement had no effect because we did not know how to make it dispensable, how to prove that there was no natural force that could replace it in the places where it had previously been considered most indispensable. Darwin proved this natural force, this natural process; he opened the door through which a happy posterity will cast the miracle out forever. Anyone who knows what the miracle depends on will praise him as one of the greatest benefactors of the human race."

Darwin's idea of expediency makes it possible to think of the concept of development in terms of natural law. The old doctrine of encasement, which assumes that everything that comes into being already existed in a hidden form (cf. Volume 1, p. 142ff. [182ff.]), was thus robbed of its last hopes. Within a process of development conceived in Darwin's sense, the perfect is in no way already contained in the imperfect. For the perfection of a higher being arises through processes that have absolutely nothing to do with the ancestors of that being. A certain series of development has reached the marsupials. In the form of the marsupials there is nothing, absolutely nothing, of a higher, more perfect form. Therein lies only the ability to transform indiscriminately in the further course of their reproduction. Now conditions arise that are independent of any “inner” developmental predisposition of the marsupial form, but which are such that, of all the possible forms of change from marsupials, prosimians are preserved. The marsupial form contained as little of the prosimian form as the direction of a rolling billiard ball contains the path it takes after being struck by a second ball.

Those who were accustomed to an idealistic way of thinking did not find it easy to accept this reformed concept of development. Friedrich Theodor Vischer, an extremely astute and refined mind who emerged from Hegel's school, wrote in an essay in 1874: "Development is an unfolding from a seed, which progresses from attempt to attempt until the image that lay as a possibility in the seed has become reality, but then remains static, holding fast to the form it has found as permanent. Every concept becomes uncertain when we consider the types that have existed on our planet for so many millennia, and especially when we consider that our own human type is still subject to change. We can then no longer trust our thoughts, our laws of thought, our feelings, the ideal images of our imagination, which are nothing more than purified replicas of forms of nature known to us: we can no longer trust any of these fixed points of reference for our soul. Everything is called into question.“ And elsewhere in the same essay we read: ”For example, I still find it somewhat difficult to believe that the eye is derived from seeing and the ear from hearing. Nor can I understand the extraordinary importance attached to selective breeding."

If Vischer had been asked whether he imagined that hydrogen and oxygen contained the seed of an image of water, so that it could develop from them, he would undoubtedly have answered: No; neither oxygen nor hydrogen contains anything of water; the conditions for the formation of this substance are only present at the moment when hydrogen and oxygen come together under certain conditions. Should it be any different when prosimians arise from the interaction of marsupials with the external conditions of existence? Why should prosimians already be hidden in marsupials as a possibility, as an image, so that they can develop from them? What arises through development arises anew, without having existed in any form before.

Prudent natural scientists felt the weight of the new doctrine of expediency no less than thinkers such as Strauss. Hermann Helmholtz undoubtedly belongs to those who could be considered representatives of such prudent natural scientists in the 1850s and 1860s. He emphasizes how the wonderful and ever-richer functionality in the structure and activities of living beings, which is unfolding before the eyes of growing science, virtually challenges us to compare life processes with human actions. For these are the only series of phenomena that bear a similar character to organic phenomena. Indeed, the functional mechanisms in the world of organisms far exceed what human intelligence is capable of creating, at least in most cases. It is therefore not surprising that people have been inclined to attribute the structure and activity of the living world to an intelligence far superior to that of humans. “Before Darwin,” says Helmholtz, "there were only two explanations for organic purposefulness, both of which attributed it to the intervention of free intelligence in the course of natural phenomena. Either, in accordance with vitalistic theory, life processes were regarded as being continuously guided by a life soul, or, for each living species, one resorted to an act of supernatural intelligence through which it was supposed to have come into being." "Darwin's theory contains an essentially new creative idea. It shows how a purposefulness of formation in organisms can arise even without any interference from intelligence, through the blind operation of a law of nature. This is the law of the inheritance of individual characteristics from parents to offspring; a law that had long been known and recognized and only needed to be defined more precisely." Helmholtz now believes that the principle of natural selection in the struggle for existence has provided such a definition of the law.

And a researcher who was no less cautious than Helmholtz, J. Fenle, explains in a lecture: "If the experiences of artificial breeding were to be applied to Oken-Lamarck's hypothesis, it would have to be shown how nature begins to take the measures of its own accord by means of which the experimenter achieves his goal. This is the task that Darwin set himself and pursued with admirable zeal and acumen. The breeder's operations are based on the perception that individual characteristics, which have developed through the influence of the soil, the climate, the exercise of individual organs, and the neglect of others, are passed on to the offspring and fixed and enhanced by continued inbreeding. The procedures by which the breeder achieves the desired breed on the basis of that perception had to be proven in the free circulation of living beings. Here Darwin found it realized through what he called natural selection, as opposed to artificial selection. According to him, it is the struggle for existence that replaces human care in freely living creatures and guarantees the perfection of the organism by allowing only the stronger, better equipped, or better protected specimens of a species to reproduce and pass on their characteristics.

The materialists were the most enthusiastic about Darwin's achievement. They had long been aware that sooner or later such a man would come along who would philosophically illuminate the accumulated body of facts that were crying out for a guiding principle. In their opinion, after Darwin's discovery, the worldview they had championed was bound to prevail.

Darwin approached his task as a naturalist. He initially remained within the boundaries of this field. The fact that his thoughts could shed light on the fundamental questions of worldview, on the relationship between humans and nature, is only touched upon in his seminal book: "In the future, I see an open field for far more important research. Psychology will certainly be based on the ... foundation: the necessity of acquiring every mental power and ability step by step. Much light may also be shed on the origin of man and his history." This question of the origin of man became a matter close to the hearts of materialists, in Büchner's words. In the lectures he gave in Offenbach in the winter of 1866-67, he said: "Must the theory of transformation also be applied to our own species, to humans or to ourselves? Must we accept that the same principles or rules that brought other organisms into being also apply to our own creation and origin? Or do we – the lords of creation – make an exception?“

Natural science clearly taught that humans could not make an exception. Based on precise anatomical studies, the English naturalist Huxley was able to state in his 1863 work ”Evidence for the Position of Man in Nature": “A critical comparison of all organs and their modifications within the ape series leads us to the same conclusion: that the anatomical differences separating humans from gorillas and chimpanzees are not as great as the differences separating these great apes from the lower ape species.” Could one still doubt such facts, that natural development, which through growth and reproduction, through heredity, variability of forms, and the struggle for existence, has brought forth the series of organic beings up to the ape, has ultimately produced man in exactly the same way?

Over the course of the century, this fundamental view became increasingly entrenched in the body of scientific knowledge, which Goethe was steeped in, and because of which he energetically set about correcting the opinion of his contemporaries that humans lacked a so-called intermaxillary bone in the upper jaw. All animals were thought to have this bone, except humans. And this was seen as proof that humans were anatomically different from animals, that they were designed differently. Goethe's natural way of thinking demanded that he conduct diligent anatomical studies to dispel this error. And when he had achieved his goal, he wrote to Herder, filled with the feeling that he had done something that was highly conducive to the understanding of nature: "I compared ... human and animal skulls, came on the trail, and lo and behold, there it is! Now I beg you, don't let on; for it must be treated as a secret. You should also be very happy about it, for it is like the keystone of humanity; if it is not missing, it is also there! But how!"

Under the influence of such ideas, the great worldview question of the relationship of humans to themselves and to the outside world became the task of using scientific methods to show what the actual processes are that led to the formation of humans in the course of evolution. This changed the perspective from which people sought to explain natural phenomena. As long as every organism, including humans, was seen as the realization of a functional blueprint, this purpose had to be taken into account when explaining these beings. One had to take into account that the later organism was already present in embryonic form. Extended to the entire universe, this meant that the best explanation of nature was one that showed how nature, in the earlier stages of its development, prepared itself to produce the later stages and, at the summit, human beings.

The modern idea of development rejected any tendency to see the later in the earlier. For it, the later was in no way contained in the earlier. On the contrary, the principle of seeking the earlier in the later became increasingly established. This principle was an integral part of the principle of heredity. One can speak of a reversal in the direction of the need for explanation. This reversal became important for the development of ideas about the development of the individual organic being from the egg to maturity, for what is known as germ history (ontogeny). Instead of assuming that the later organs are prepared in the embryo, scientists began to compare the forms that the organism takes in the course of its individual development from egg to maturity with other organism forms. Lorenz Oken had already pursued this line of thought. In the fourth volume of his “General Natural History for All Classes” ($. 468), he wrote: "Through my physiological investigations, I came to the conclusion a number of years ago that the stages of development of the embryo in the egg are similar to the different classes of animals, so that at first it possesses only the organs of infusoria, then gradually acquires those of polyps, jellyfish, mussels, snails, etc. Conversely, I then had to regard the animal classes as stages of development that paralleled those of the chick. This view of nature required the most precise comparison of those organs that are newly added to the others in each higher animal class, and likewise of those that develop successively in the chick during incubation. Of course, it is not so easy to establish complete parallelism with such a difficult subject that has not yet been sufficiently observed. However, proving that it really exists is not difficult: this is most clearly demonstrated by the metamorphosis of insects, which is nothing more than the development of the young outside the egg before our eyes, and so slowly that we can observe and examine each embryonic stage at leisure." Oken compares the stages of transformation in insects with those in other animals and finds that caterpillars bear the greatest resemblance to worms, while pupae resemble crabs. From such similarities, the brilliant thinker concludes: “There is therefore no doubt that there is a striking similarity here, which justifies the idea that the history of development in the egg is nothing more than a repetition of the history of the creation of the animal classes.” It was in the nature of this brilliant man to intuit a great idea based on a fortunate aperçu. He did not even need the corresponding complete facts for such an intuition. But it is also in the nature of such intuited ideas that they do not make a great impression on those working in the field of science. Oken flashes like a comet in the German worldview sky. He developed a wealth of light. From a rich store of ideas, he provided guiding concepts for a wide variety of factual areas. However, the way he arranged factual connections was mostly somewhat forceful. He worked toward the punchline. This was also the case with the above-mentioned law of the repetition of certain animal forms in the embryonic development of others.

In contrast to Oken, Carl Ernst von Baer stuck as closely as possible to the facts when he wrote about what had led Oken to his idea in his 1828 work “Entwickelungsgeschichte der Tiere” (History of Animal Development). "The embryos of mammals, birds, lizards, and snakes, and probably also of turtles, are extremely similar to each other in their early stages, both as a whole and in the development of their individual parts; so similar that the embryos can often only be distinguished by their size. I have two small embryos in alcohol, for which I neglected to note the names; and I am now completely unable to determine the class to which they belong. They could be lizards, small birds, or very young mammals. The formation of the head and torso in these animals is so similar. However, these embryos still lack limbs. Even if they were present, in the first stage of development, they would not teach us anything, since the feet of lizards and mammals, the wings and feet of birds, and the hands and feet of humans develop from the same basic form.

Such facts of embryonic history had to arouse the greatest interest among those thinkers who were inclined toward Darwinism with their convictions. Darwin had proven the possibility that organic forms change and that, through transformation, the species living today descend from a few, perhaps only one, original species. Now, the manifold living creatures appear so similar in their early stages of development that it is difficult or even impossible to distinguish between them. In 1864, Fritz Müller brought both this fact of similarity and the idea of descent into organic connection in a thoughtful essay entitled “For Darwin.” Müller is one of those highly sensitive personalities whose souls absolutely need a natural worldview in order to breathe spiritually. He also found satisfaction in his own actions only when he could feel that his motives were as necessary as a force of nature. He wanted to become a senior teacher and asked the Prussian ministry not to require him to take the civil servant's oath. It was contrary to his free-thinking sensibilities to pronounce the religious wording of the oath. His request was denied. As a result, he could never hope to have a sphere of influence in the state. In 1852, Müller moved to Brazil. For twelve years, he held a position as a high school teacher in Desterro (on the island of Santa Catharina, not far from the coast of Brazil). In 1867, he was forced to give up this position as well. The man with the new worldview had to give way to the reaction that took hold of his educational institution under the influence of the Jesuits. Ernst Haeckel described the life and work of Fritz Müller in the “Jenaische Zeitschrift für Naturwissenschaft” (XXX. Band N.E XXIV. 1897). Darwin called him the “prince of observers.” And from a wealth of observations, the small but significant work “Für Darwin” (For Darwin) was born. It dealt with a single group of organic forms, crabs, in the spirit that Fritz Müller believed must result from Darwin's view. He showed that crab forms, which differ from each other in their mature states, are completely similar to each other at the time they hatch from the egg. If we assume that, in accordance with Darwin's theory of evolution, the crab forms developed from a primordial crab form, and if we assume that the similarity in the juvenile stages of these animals is a legacy from their common ancestral form, then we have combined Darwin's ideas with those of Oken regarding the repetition of the history of creation of the animal classes in the development of the individual animal form. Fritz Müller also accomplished this unification. In doing so, he brought the early forms of an animal class into a certain lawful connection with the later ones that were formed from them through transformation. The fact that an ancestral form of a creature living today once looked a certain way has caused this creature living today to look a certain way at a certain stage of its development. The developmental stages of organisms reveal their ancestors, and the nature of the latter determines the characteristics of the embryonic forms. Phylogeny and ontogeny are linked in Fritz Müller's book like cause and effect. This brought a new dimension to Darwin's ideas. This is not weakened by the fact that Müller's cancer research was modified by Arnold Lang's later investigations.

Only four years had passed since the publication of Darwin's book “On the Origin of Species” when Müller's treatise appeared in its defense and confirmation. He had shown, using a single class of animals, how to work in the spirit of the new ideas. Seven years after On the Origin of Species, in 1866, a book appeared that was thoroughly imbued with this new spirit, illuminating the connection between the phenomena of life from a lofty perspective with the ideas of Darwinism: Ernst Haeckel's General Morphology of Organisms. Every page of this book reveals the great goal of using the new ideas to take a look at the entirety of natural phenomena. Haeckel sought a worldview based on Darwinism.

Haeckel strove in two directions to do as much as possible for the new worldview: he incessantly enriched knowledge of the facts that shed light on the connection between natural beings and natural forces; and he drew with iron consistency from these facts the ideas that were to satisfy the human need for explanation. He is imbued with the unshakeable conviction that man can derive complete satisfaction for all his spiritual needs from these facts and ideas. As Goethe clearly understood, so too does he, that nature operates according to eternal, necessary, divine laws that even the deity itself cannot change. And because this is clear to him, he worships his deity in the eternal and necessary laws of nature and in the substances on which these laws operate. Just as the harmony of the laws of nature, which are necessarily interrelated, satisfies reason according to his view, so it also offers the feeling heart, the ethically and religiously minded soul, what it thirsts for. The same divinity is expressed in the stone that is attracted to the earth and falls toward it as in the blossom of a plant and in the human spirit that dramatically shapes “William Tell.”

How mistaken it is to believe that a rational understanding of the workings of nature, through research into its laws, destroys our sense of its wonderful beauty, is clearly demonstrated by the work of Ernst Haeckel. Rational explanations of nature have been denied the ability to satisfy the needs of the mind. It can be said that wherever a person's emotional world is impaired by knowledge of nature, this is not due to this knowledge, but to the person whose feelings are moving in the wrong direction. Anyone who follows the research paths of a nature observer such as Haeckel with an open mind will feel their heart beat faster with every step they take in the knowledge of nature. Anatomical dissection and microscopic examination will not destroy the beauty of nature for them, but will reveal countless new aspects of it. There is no doubt that in our time there is a struggle between reason and imagination, between reflection and intuition. Ellen Key, the witty essayist, is absolutely right when she sees this struggle as one of the most important phenomena of the present day (cf. Ellen Key: “Essays.” Berlin, S. Fischer Verlag, 1899). Those who, like Ernst Haeckel, delve deep into the shaft of facts and boldly ascend with the thoughts that arise from these facts to the peaks of human knowledge can only find in the explanation of nature the reconciling power “between the two equally strong runners, reflection and intuition, which bring each other to their knees.” (Ellen Key, ibid.). Almost simultaneously with the publication in which Haeckel presents his worldview, flowing from his knowledge of nature, with the strictest logical consistency, with the publication of his “Welträtsel” (The Riddle of the Universe) in 1899, he began publishing a series of works: " Kunstformen der Natur“ (Art Forms in Nature), in which he provides reproductions of the inexhaustible wealth of wonderful forms that nature produces in its bosom and which far surpass ”all art forms created by man" in beauty and diversity. The same man who guides our understanding into the laws of nature directs our imagination to the beauty of nature.

The need to bring the great questions of worldview into direct contact with individual scientific investigations led Haeckel to one of those facts which Goethe says mark concise points at which nature voluntarily gives up the basic ideas for its explanation and presents them to us. This fact presented itself to Haeckel as he investigated the extent to which Oken's old idea, which Fritz Müller applied to crustaceans, could be fruitfully applied to the entire animal kingdom. In all animals, with the exception of protists, which consist of only one cell throughout their lives, the egg cell, with which the organism begins its embryonic development, forms a cup-shaped or jug-shaped body, the so-called cup germ or gastrula. This cup germ is an animal form that all animals, from sponges to humans, assume in their first stage of development. This form has only skin, mouth, and stomach. Now there are lower plant animals that have only these organs throughout their lives, which are therefore similar to the cup germ. Haeckel interpreted this fact in terms of evolutionary theory. The gastrula form is an inheritance that animals have inherited from their common ancestral form. There was probably a species of animal that became extinct millions of years ago, the Gastraea, which was similar in structure to the lower plant animals still living today: sponges, polyps, etc. Everything that lives today in the manifold forms between polyps, sponges, and humans developed from this species of animal. All these animals repeat their ancestral form in the course of their embryonic development.

An idea of enormous significance was thus gained. The path from the simple to the complex, to perfection in the world of organisms, was mapped out. A simple animal form develops under certain circumstances. One or more individuals of this form transform into another form according to the living conditions they encounter. What has been created through transformation is passed on to offspring. Two forms already exist. The old one, which has remained at the first stage, and a new one. Both forms can continue to develop in different directions and degrees of perfection. After long periods of time, a wealth of species emerges through the inheritance of the forms that have developed and through new formations in the process of adaptation to living conditions.

Thus, for Haeckel, what is happening in the world of organisms today is connected to what happened in primeval times. If we want to explain any organ in an animal of our present day, we look back to the ancestors who developed this organ under the conditions in which they lived. What arose in earlier times from natural causes has been passed down to the present day. The history of the species explains the development of the individual. The causes of individual development (ontogenesis) thus lie in the development of the species (phylogenesis). Haeckel expresses this fact in his biogenetic law with the words: “The short ontogenesis, or development of the individual, is a rapid and condensed repetition, a condensed recapitulation of the long phylogeny, or development of the species.”

This removes all explanation in the sense of special purposes, all teleology, from the realm of the organic. One no longer searches for the purpose of an organ; one searches for the causes from which it developed; a form does not point to the goal it strives for, but to the origin from which it emerged. The way of explaining the organic has become the same as that of the inorganic. One does not search for water as the goal in oxygen, nor does one search for man as the purpose in creation. One searches for the origin, for the actual causes of beings. The dualistic view, which explains that the inorganic and the organic must be explained according to two different principles, is transformed into a monistic way of thinking, into monism, which has only one unified explanation for the whole of nature.

Haeckel points out in significant words that his discovery has found the way in which all dualism must be overcome. "Phylogenesis is the mechanical cause of ontogenesis. This one sentence clearly defines our fundamental monistic view of organic development, and the truth of the gastrulation theory depends primarily on the truth of this principle.... In the future, every natural scientist who is not content with merely admiring strange phenomena in biogeny, but who strives to understand their meaning, will have to decide for or against this principle. This sentence also describes the unbridgeable gap that separates the older teleological and dualistic morphology from the newer mechanical and monistic one. If the physiological functions of heredity and adaptation are proven to be the sole causes of organic form formation, then any kind of teleology, dualistic and metaphysical approach is removed from the field of biogeny; the sharp contrast between the guiding principles is thus clearly defined. Either there is a direct and causal connection between ontogeny and phylogeny, or there is not. Either ontogenesis is a condensed extract of phylogenesis, or it is not. There is no third option between these two assumptions! Either epigenesis and descent – or preformation and creation." (See also “Welt- und Lebensanschauungen” [Worldviews and Views on Life], Volume 1, p. 142ff. [182ff.]) Haeckel is a philosophical thinker. Therefore, soon after he had absorbed Darwin's view, he energetically advocated the important conclusion that this view leads to regarding the origin of man. He could not content himself with timidly hinting at this “question of all questions,” as Darwin did. Humans do not differ anatomically and physiologically from higher animals, so they must also be attributed the same origin as these. With great boldness, he immediately advocated this opinion and all the consequences that follow from it in terms of worldview. He had no doubt that from then on, the highest expressions of human life, the deeds of the human mind, were to be viewed from the same perspective as the activities of the simplest living creatures. The observation of the lowest animals, the protozoa, infusoria, and rhizopods, taught him that these organisms also have a soul. In their movements, in the hints of sensations that they reveal, he recognized expressions of life that only need to become more intense and more perfect in order to become the complex acts of reason and will of humans.

What steps does nature take to progress from the gastraca, the primitive intestinal animal that lived millions of years ago, to humans? That was the comprehensive question Haeckel asked himself. He provided the answer in his “Anthropogeny,” published in 1874. The first part deals with the germ history of humans, and the second with their phylogenetic history. Point by point, he showed how the latter is the cause of the former. The position of humans in nature was thus determined according to the principles of evolutionary theory. Works such as Haeckel's Anthropogeny can be described in the words of the great anatomist Carl Gegenbaur in his Comparative Anatomy (1870), who said that Darwinism as a theory receives back from science what it has given to it in terms of method: clarity and certainty. Using the Darwinian method, Haeckel gave science the theory of human origins.

The full extent of what this achieved can only be appreciated when one considers the opposition with which Haeckel's comprehensive application of Darwinian principles was received by the adherents of theological and idealistic worldviews. There is no need to look at those who, in their blind faith in a traditional doctrine, turned against the “monkey theory,” or at those who believe that all finer, higher morality is endangered if people no longer believe that they have a “purer, higher origin.” One can also look to those who are quite inclined to accept new truths. But even they found it difficult to come to terms with this new truth. They asked themselves: Are we not denying our rational thinking when we no longer seek its origin in a general world reason above us, but in the animal kingdom below us? Such minds pointed out with great zeal the points where Haeckel's view still seemed to be contradicted by the facts. And these minds have powerful allies in a number of natural scientists who, out of a strange bias, use their knowledge of facts to constantly emphasize where experience is not yet sufficient to draw Haeckel's conclusions. The typical representative and at the same time the most impressive proponent of this natural scientist's point of view is Rudolf Virchow. The contrast between Haeckel and Virchow can be characterized as follows. Haeckel trusts in the internal consistency of nature, which Goethe believes compensates for the inconsistency of humans, and says to himself: If a natural principle has proven to be correct in certain cases and we lack the experience to prove its correctness in other cases, there is no reason to shackle the progress of our knowledge; what experience denies us today may be brought to us tomorrow. Virchow disagrees. He wants to allow a comprehensive principle to gain as little ground as possible. He seems to believe that one cannot make life difficult enough for such a principle. The contrast between the two minds came to a head at the fiftieth meeting of German naturalists and physicians in September 1877. Haeckel gave a lecture on “The current theory of evolution in relation to science as a whole.” With great enthusiasm, he described the impact that the new doctrine must have on our entire intellectual culture. Convinced that the revolution in our most important views initiated by Darwin must affect not only the natural sciences but also the humanities, he called on the education system to take the new doctrine into account. Four days later, Virchow gave a speech entitled “The Freedom of Science in the Modern State.” At first, it seemed as if he wanted to banish the monistic worldview from schools because he considered it a mere hypothesis, not a fact proven by reliable evidence. But one must also be wary of such a project when Virchow says: “Any attempt to transform our problems into doctrines, to introduce our assumptions as the basis of teaching, [...] must fail, and in its failure it will at the same time bring about the greatest dangers for science.” Three years after the publication of Haeckel's Anthropogeny, Virchow thus speaks of the monistic worldview as a “conjecture.” And his entire attitude toward Haeckel shows that he considers the latter's conclusions to be nothing more than “conjectures.” He seized every opportunity to counter these conclusions with the apparent impotence of empirical knowledge. At the twenty-fifth anniversary celebration of the “German Anthropological Society” in 1894, he felt compelled to say: "Speculation has led to the ape theory; one could just as well have arrived at an elephant or a sheep theory." Virchow's tactic toward monism is a highly peculiar one. He demands irrefutable proof for this view. But as soon as something appears that could be a link in the chain of evidence, Virchow seeks to invalidate its value in every possible way.

One such link in the chain of evidence is the bone remains found by Eugen Dubois in Java in 1894. They consist of a skull cap, a thigh bone, and several teeth. This discovery sparked an interesting discussion at the Leyden Zoological Congress. Of twelve zoologists, three were of the opinion that the bone remains came from an ape, three that they came from a human being, but six were of the opinion that they were a transitional form between humans and apes. Dubois has shown in a convincing manner the relationship between the creature whose remains were before them and, on the one hand, present-day apes and, on the other hand, present-day humans. The theory of evolution must make particular use of such intermediate forms. They fill the gaps that exist between the numerous forms of organisms. Each such intermediate form provides new evidence of the kinship of all living things. Virchow opposed the view that the bone remains came from such an intermediate form. He initially declared that the skull came from an ape and the thigh bone from a human. However, after careful examination of the find report, expert paleontologists spoke out decisively in favor of the remains belonging together. Virchow sought to support his view that the thigh bone could only have come from a human by claiming that a bone growth on it proved that the individual had suffered from an illness that could only have been cured through careful human care. However, the paleontologist Marsh argued that similar bone growths also occur in wild apes. Virchow's further assertion that the deep constriction between the upper edge of the eye sockets and the lower skull of the supposed intermediate creature indicated its ape-like nature was contradicted by a remark by the naturalist Nehring that the same formation could be found on a human skull from Santos in Brazil. Virchow's objections stemmed from the same mindset that led him to see pathological, abnormal formations in the famous skulls of Neanderthal, Spy, etc., while Haeckel's like-minded colleagues considered them to be intermediate forms between apes and humans.

Haeckel did not allow any objections to rob him of his confidence in his way of thinking. He relentlessly pursued rigorous science from the perspectives he had gained, and he influenced public consciousness through popular presentations of his view of nature. In his "Systematic Phylogeny. Draft of a Natural System of Organisms Based on Phylogeny“ (1894-1896), he presented the natural relationships between organisms in a strictly scientific manner. In his ”Natural History of Creation," which went through nine editions between 1868 and 1897, he presented a generally understandable discussion of his views. In his widely accessible studies on monistic philosophy, “The Riddle of the Universe,” published in 1899, he provided an overview of his ideas on natural philosophy, unreservedly presenting the conclusions of his fundamental thoughts from all angles. In between all these works, he published studies on a wide variety of specialized research topics, always giving equal consideration to philosophical principles and scientific detail.

According to Haeckel's conviction, the light that emanates from the monistic worldview is the one that “dispels the heavy clouds of ignorance and superstition that have hitherto spread impenetrable darkness over the most important of all problems of knowledge, over the question of the origin of man, his true nature, and his place in nature.” This is how he expressed himself in the speech he gave on August 26, 1898, at the Fourth International Zoological Congress in Cambridge, entitled “On Our Present Knowledge of the Origin of Man.” Haeckel forcefully explained the extent to which his worldview forms a link between religion and science in his 1892 publication “Monism as a Link between Religion and Science: The Creed of a Natural Scientist.”

Comparing Haeckel with Hegel reveals the sharp contrast between their worldviews in the two halves of the nineteenth century. Hegel lives entirely in the realm of ideas and takes from the world of scientific facts only as much as he needs to illustrate his ideal worldview. Haeckel is rooted with every fiber of his being in the world of facts and draws from it only the sum of ideas to which it necessarily leads. Hegel always strives to show how all beings work toward ultimately reaching the pinnacle of their development in the human spirit; Haeckel is always trying to prove how the most complicated human activities can be traced 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 thinking over the course of the century. Within German intellectual life, Strauss, Feuerbach, and others initiated this reversal; in materialism, the new direction found a provisional, extreme expression, and in Haeckel's world of ideas, a strictly methodical and scientific one. For what is significant about Haeckel is that his entire research activity is permeated by a philosophical spirit. He does not work toward results that are set as goals of worldview or philosophical thinking for whatever reasons; but his approach is philosophical. For him, science appears directly with the character of worldview. His entire way of looking at things has determined him to be a believer in the most decisive monism. He views spirit and nature with equal love. That is why he was able to find spirit even in the simplest living beings. Indeed, he goes even further. He searches for traces of spirit in inorganic particles of matter. “Every atom,” he says, "possesses a force and is, in this sense, ‘animated.’ Without the assumption of an ‘atomic soul,’ the most common and general phenomena of chemistry are inexplicable. Pleasure and displeasure, desire and aversion, attraction and repulsion must be common to all mass atoms; for the movements of atoms that must take place during the formation and dissolution of every chemical compound can only be explained if we attribute sensation and will to them. And it is only on this that the generally accepted chemical theory of affinity is based." And just as he traces the spirit down to the atom, so he traces purely material-mechanical events up to the most sublime achievements of the spirit. "The ‘spirit’ and ‘soul’ of man are also nothing more than forces that are inseparably bound to the material substrate of our body. Just as the motor function of our flesh is bound to the structural elements of our muscles, so the thinking power of our mind is bound to the structural elements of our brain. Our mental powers are simply functions of these parts of the body, just as every ‘power is the function of a material body.’"

However, this way of thinking should not be confused with the mystical notion of projecting souls onto natural beings and making them more or less similar to human beings. Haeckel is a fierce opponent of the worldview that transfers human characteristics and activities to the outside world. He has repeatedly expressed his condemnation of the humanization of nature, of anthropomorphism, with unmistakable clarity. When he attributes animism to inorganic matter or the simplest organisms, he means nothing more than the sum of the expressions of force that we observe in them. He sticks strictly to the facts. For him, the sensation and will of the atom are not mystical soul forces, but are exhausted in what we perceive as attraction and repulsion. He does not mean to say that attraction and repulsion are actually sensation and will, but that attraction and repulsion are, at the lowest level, what sensation and will are at a higher level. Development is not merely the emergence of the higher levels of the spiritual from the lower, in which they are already hidden, but a real ascent to new formations (cf. above p. 43f. [269f.]), an increase from attraction and repulsion to sensation and will. This fundamental view of Haeckel is entirely consistent with that of Goethe, who expresses it in the following words: the fulfillment of his view of nature came to him through the recognition of the “two great driving forces of all nature,” polarity and intensification, the former "belonging to matter insofar as we think of it materially, the latter insofar as we think of it spiritually; the former is in perpetual attraction and repulsion, the latter in perpetual ascent. But because matter can never exist and be effective without spirit, and spirit can never exist and be effective without matter, matter is also capable of ascent, just as spirit cannot refrain from attracting and repelling."

Those who profess such a worldview are content to deduce the things and processes that actually exist in the world. Idealistic worldviews require entities that are not found within the realm of the actual in order to deduce a thing or process. Haeckel derives the form of the cup germ, which appears in the course of animal development, from an organism that actually once existed. An idealist searches for ideal forces under whose influence the developing germ becomes a gastrula. Haeckel's monism draws everything it needs to explain the real world from this real world itself. He looks around in the realm of the real to see how things and processes explain each other. Unlike the idealist, his theories are not there to seek something higher than the actual, an ideal content that explains the real, but to make the connection between the actual things themselves comprehensible to him. Fichte, the idealist, asked about the purpose of human beings. By this he meant something that is not exhausted in the forms of the real, the actual; he meant something that reason finds in addition to actual existence; something that illuminates the real existence of human beings with a higher light. Haeckel, the monistic observer of the world, asks about the origin of man, and by that he means the real origin, the lower beings from which man has developed through actual processes.

It is significant how Haeckel justifies the animation of lower living beings. An idealist would refer to rational conclusions. He would come up with intellectual necessities. Haeckel refers to what he has seen. "Every natural scientist who, like me, has observed the life activity of single-celled protists for many years is positively convinced that they too possess a soul; this cellular soul also consists of a sum of sensations, ideas, and volitional activities; the feeling, thinking, and willing of our human souls is only gradually different from it." The idealist attributes spirit to matter because he cannot imagine that spirit can arise from spiritless matter. He believes that one must deny the spirit if one does not allow it to be there before it is there, i.e., in all forms of existence where there is no organ, no brain for it yet. For the monist, such a train of thought does not exist. He does not speak of an existence that does not also manifest itself externally. He does not assign two kinds of properties to things: those that are real and manifest themselves in them, and those that are secretly within them, only to manifest themselves at a higher stage to which things develop. For him, what he observes is there; nothing more. And if what is observed develops further and intensifies in the course of its development, the later forms are only present at the moment when they actually manifest themselves.

The objections raised by the brilliant Bartholomäus von Carneri, who on the other hand made an indelible contribution to the development of an ethic based on this worldview, show how easily Haeckel's monism can be misunderstood in this direction. In his work "Empfindung und Bewußtsein. Monistic Concerns“ (1893), he argues that the statement ”No spirit without matter, but also no matter without spirit" would entitle us to extend the question to plants, even to the nearest boulder, and to attribute spirit to them as well. However, he adds that this would undoubtedly create confusion. It cannot be overlooked that consciousness arises only through the activity of the cells of the gray cerebral cortex. “The conviction that there is no spirit without matter, i.e., that all mental activity is bound to material activity, with whose end it also reaches its end, is based on experience; while nothing in experience suggests that spirit is connected with matter at all.” Anyone who animates matter, which reveals no spirit, is like someone who attributes the ability to tell the time not to the mechanism of the clock, but to the metal from which it is made.

Haeckel's view, correctly understood, is not affected by Carneri's concerns. It is protected from this by the fact that it adheres strictly to observation. In his “Welträtseln” (World Riddles), Haeckel says: “I myself have never advocated the hypothesis of atomic consciousness ... Rather, I have expressly emphasized that I imagine the elementary psychic activities of sensation and will, which can be attributed to atoms, to be unconscious.” What Haeckel wants is nothing more than that no leap be made in the explanation of natural phenomena, that the complicated way in which the mind arises through the brain be traced back to the simplest way in which mass attracts and repels itself. Haeckel considers Paul Flechsig's discovery of the thinking organs to be one of the most important findings of modern science. Flechsig proved that in the gray cortical zone of the cerebral cortex there are four areas for the central sensory organs, four “inner spheres of sensation”: the sphere of bodily sensation, the sphere of smell, the sphere of taste, and the sphere of hearing. Between these four sensory centers lie the centers of thought, the "real organs of mental life; they are the highest tools of soul activity, which mediate thinking and consciousness.“ ”These four thinking centers, distinguished from the sensory centers between them by a peculiar and highly complex nerve structure, are the true ‘thinking organs,’ the only organs of our consciousness. Recently, Flechsig has demonstrated that in one part of these centers, humans have particularly complex structures that are lacking in other mammals, which explain the superiority of human consciousness.“ (”Welträtsel," p. 212f.)

Such statements show clearly enough that Haeckel, unlike the idealistic explainers of the world, is not concerned with placing the spirit in the lower stages of material existence in order to rediscover it in the higher stages, but rather with following the simple phenomena to the complex ones on the basis of observation in order to show how the activity of matter, which manifests itself in the primitive realm as attraction and repulsion, intensifies to higher spiritual activities.

Haeckel does not seek a general spiritual principle because he is not satisfied with the general laws of natural and spiritual phenomena, but rather because he is completely satisfied with these general laws. For him, the laws that express themselves in spiritual activities are of the same nature as those that manifest themselves in the attraction and repulsion of material particles. When he calls atoms animated, this has a completely different meaning than when someone who professes an idealistic worldview does so. The latter starts from the spirit and takes the ideas he has gained from contemplating the spirit down into the simple activities of atoms when he thinks of them as animated. He thus explains natural phenomena from the entities that he himself has first placed in them. Haeckel starts from the observation of the simplest natural phenomena and traces them up to spiritual activities. He thus explains spiritual phenomena from laws that he has observed in the simplest natural phenomena.