Ernst Haeckel

Life and death—Individual death—Immortality of the unicellulars—Death of the protists and tissue-organisms—Causes of physiological death—Using up of the plasma—Regeneration—Biotonus—Perigenesis of the plastidules: memory of the biogens—Regeneration of protists and tissue-organisms—Senile debility—Disease—Necrobiosis—The lot of death—Providence—Chance and fate—Eternal life—Optimism and pessimism—Suicide and self-redemption—Redemption from evil—Medicine and philosophy—Maintenance of life—Spartan selection.

Nothing is constant but change! All existence is a perpetual flux of "being and becoming"! That is the broad lesson of the evolution of the world, taken as a whole or in its various parts. Substance alone is eternal and unchangeable, whether we call this all-embracing world-being Nature, or Cosmos, or God, or World-spirit. The law of substance teaches us that it reveals itself to us in an infinite variety of forms, but that its essential attributes, matter and energy, are constant. All individual forms of substance are doomed to destruction. That will be the fate of the sun and its encircling planets, and of the organisms that now people the earth—the fate of the bacterium and of man. Just as the existence of every organic individual had a beginning, it will also undeniably have an end. Life and death are irrevocably united. However, philosophers and biologists hold very different views as to the real causes of this destiny. Most of their opinions are at once out of court, because they have not a clear idea of the nature of life, and so can have no adequate idea of its termination—death.

The inquiry into the nature of organic life which we instituted in the second chapter has shown us that it is, in the ultimate analysis, a chemical process. The "miracle of life" is in essence nothing but the metabolism of the living matter, or of the plasm. Recent physiologists, especially Max Verworn and Max Kassowitz, have pointed out, in opposition to modern vitalism, that "life consists in a continuous alternation between the upbuild and the decay of the highly complicated chemical unities of the protoplasm. And if this conception is admitted, we may rightly say that we know what we mean by death. If death is the cessation of life, we must mean by that the cessation of the alternation between the upbuild and the dissolution of the molecules of protoplasm; and as each of the molecules of protoplasm must break up again shortly after its formation, we have in death to deal only with the definite cessation of reconstruction in the destroyed plasma-molecules. Hence a living thing is not finally dead—that is to say, absolutely incompetent to discharge any further vital function—until the whole of its plasma-molecules are destroyed." In the exhaustive justification with which Kassowitz follows up this definition in the fifteenth chapter of his General Biology, the natural causes of physiological death are fully described.

Among the numerous and contradictory views of recent biologists on the nature of death we find many errors and misunderstandings, due to a lack of clear distinction between the duration of the living matter in general and that of the individual life-form. This is particularly noticeable in the contradictory views which have been elicited by August Weismann's theory (1882) of the immortality of the unicellulars. I have shown in the eleventh chapter of the Riddle that it is untenable. But as the distinguished zoologist has again taken up his theory with energy in his instructive Lectures on the Theory of the Descent (1902), and has added to it erroneous observations on the nature of death, I am obliged to return to the point. Precisely because this interesting work gives most valuable support to the theory of evolution, and maintains Darwin's theory of selection and its consequences with great effect, I feel it is necessary to point out considerable weaknesses and dangerous errors in it. The chief of these is the important theory of the germ-plasm and the consequent opposition to the inheritance of acquired characteristics. Weismann deduces from this a radical distinction between the unicellular and the multicellular organisms. The latter alone are mortal, the former immortal; "between the unicellular and the multicellular lies the introduction of physiological—that is to say, normal—death." We must say, in opposition to this, that the physiological individuals (bionta) among the protista are just as limited in their duration as among the histona. But if the chief stress in the question is laid, not on the individuality of the living matter, but on the continuity of the metabolic life-movement through a series of generations, it is just as correct to affirm a partial immortality of the plasm for the multicellulars as for the unicellulars.

The immortality of the unicellulars, on which Weismann has laid so much stress, can only be sustained for a small part of the protists even in his own sense—namely, for those which simply propagate by cleavage, the chromacea and bacteria among the monera (chapter ix.), the diatomes and paulotomes among the protophyta, and a part of the infusoria and rhizopods among the protozoa. Strictly speaking, the individual life is destroyed when a cell splits into two daughter-cells. One might reply with Weismann that in this case the dividing unicellular organism lives on as a whole in its offspring, and that we have no corpse, no dead remains of the living matter, left behind. But that is not true of the majority of the protozoa. In the highly developed ciliata the chief nucleus is lost, and there must be from time to time a conjugation of two cells and a mutual fertilization of their secondary nuclei, before there can be any further multiplication by simple cleavage. However, in most of the sporozoa and rhizopoda, which generally propagate by spore formation, only one portion of the unicellular organism is used for this; the other portion dies, and forms a "corpse." In the large rhizopods (thalamophora and radiolaria) the spore-forming inner part, which lives on in the offspring, is smaller than the decaying outer portion, which becomes the corpse.

Weismann's view of the secondary "introduction of physiological death in the multicellulars" is just as untenable as his theory of the immortality of the unicellulars. According to this opinion, the death of the histona—both the metaphyta and metazoa—is a purposive outcome of adaptation, only introduced by selection when the multicellular organism has reached a certain stage of complexity of structure, which is incompatible with its original immortality. Natural selection would thus kill the immortal and preserve only the mortal; it would interfere with the multiplication of the immortals in the bloom of their years, and only use the mortal for rearing posterity. The curious conclusions which Weismann reached in developing this theory of death, and the striking contradictions to his own theory of the germ-plasm which he fell into, have been pointed out by Kassowitz in the forty-ninth chapter of his General Biology. In my opinion, this paradoxical theory of death has no more basis than the germ-plasm theory he has ingeniously connected with it. We may admire the subtlety and depth of the speculations with which Weismann has worked out his elaborate molecular theory. But the nearer we get to its foundations the less solid we find them. Moreover, not one of the many supporters of the theory of germ-plasm has been able to make profitable use of it in the twenty years since it was first published. On the other hand, it has had an evil influence in so far as it denied the inheriting of acquired characters, which I hold, with Lamarck and Darwin, to be one of the soundest and most indispensable supports of the theory of descent.

In discussing the question of the real causes of death, we confine our attention to normal or physiological death without considering the innumerable causes of accidental or pathological death, by illness, parasites, mishaps, etc. Normal death takes place in all organisms when the limit of the hereditary term of life is reached. This limit varies enormously in different classes of organisms. Many of the unicellular protophyta and protozoa live only a few hours, others several months or years; many one-year plants and lower animals live only a summer in our temperate climate, and only a few weeks or months in the arctic circle or on the snow-covered Alps. On the other hand, the larger vertebrates are not uncommonly a hundred years old, and many trees live for a thousand years. The normal span of life has been determined in all species in the course of their evolution by adaptation to special conditions, and has then been transmitted to offspring by heredity. In the latter, however, it is often subject to considerable modifications.

The organism has been compared, on the modern "machine theory" of life, to an artificially constructed mechanism, or an apparatus in which the human intelligence has put together various parts for the attainment of a certain end. This comparison is inapplicable to the lowest organisms, the monera, which are devoid of such a mechanical structure. In these primitive "organisms without organs" (chromacea and bacteria) the sole cause of life is the invisible chemical structure of the plasm and the metabolism effected by this. As soon as this ceases death takes place (cf. chapter ix.). In the case of all other organisms the comparison is useful in so far as the orderly co-operation of the various organs or parts accomplishes a certain task by the conversion of virtual into active force. But the great difference between the two is that in the case of the machine the regularity is due to the purposive and consciously acting will of man, whereas in the case of the organism it is produced by unconscious natural selection without any design. On the other hand, the two have another important feature in common in the limited span of life which is involved in their being used up. A locomotive, ship, telegraph, or piano, will last only a certain number of years. All their parts are worn out by long use, and, in spite of all repairing, become at last useless. So in the case of all organisms, the various parts are sooner or later worn out and rendered useless; this is equally true of the organella of the protist and the organs of the histon. It is true that the parts may be repaired or regenerated; but sooner or later they cease to be of service, and become the cause of death.

When we take the idea of regeneration, or the recuperation of parts that have been rendered useless, in the widest sense, we find it to be a universal vital function of the greatest importance. The whole metabolism of the living organism consists in the assimilation of plasm, or the replacing of the plasma-particles which are constantly used up by dissimilation (cf. chapter x.). Verworn has given the name of biogens to the hypothetical molecules of living matter—which I regard with Hering as endowed with memory, and (1875) have called plastidules. He says: "The biogens are the real vehicles of life. In their constant decay and reconstruction consists the process of life, which expresses itself in the great variety of vital phenomena." The relation of assimilation (the building-up of the biogens) to dissimilation (the decay of the biogens) may be expressed by a fraction to which the name biotonus is given A/D. It is of radical importance in the various phenomena of life. The variations in the size of this fraction are the cause of all change in the life-expression of every organism. When the biotone increases, and the metabolism quotient becomes more than one, we have growth; when, on the other hand, it falls below one, and the biotone decreases, we have atrophy, and finally death. New biogens are constructed in regeneration. In generation or reproduction groups of biogens (as germ-plasm) are released from the parent in consequence of redundant growth, and form the foundation of new individuals.

The phenomena of regeneration are extremely varied, and have of late years been made the subject of a good deal of comprehensive experiment, especially on the side of what is called "mechanical embryology." Many of these experimental embryologists have drawn far-reaching conclusions from their somewhat narrow experiments, and have partly urged them as objections to Darwinism. They imagine that they have disproved the theory of selection. Most of these efforts betray a notable lack of general physiological and morphological knowledge. As they also generally ignore the biogenetic law, and take no account of the fundamental correlation of embryology and stem history, we can hardly wonder that they reach the most absurd and contradictory conclusions. Many examples of this will be found in the Archiv fÜr Entwickelungsmechanik. When, however, we make a comprehensive survey of the interesting field of regeneration processes, we discover a continuous series of development from the simplest repair of plasm in the unicellular protists to the sexual generation of the higher histona. The sperm-cells and ova of the latter are redundant growth-products, which have the power of regenerating the whole multicellular organism. But many of the higher histona have also the capacity to produce new individuals by regeneration from detached pieces of tissue, or even single cells. In the peculiar mode of metabolism and growth which accompanies these processes of regeneration, the memory of the plastidule, or the unconscious retentive power of the biogens, plays the chief part (cf. my Perigenesis of the Plastidule, 1875). In the most primitive kinds of the unicellular protists we find the phenomena of death and regeneration in the simplest form. When an unnucleated moneron (a chromaceum or bacterium) divides into two equal halves, the existence of the dividing individual comes to an end. Each half regenerates itself in the simplest conceivable way by assimilation and growth, until it, in turn, reaches the size of the parent organism. In the nucleated cells of most of the protophyta and protozoa it is more complicated, as the nucleus becomes active as the central organ and regulator of the metabolism. If an infusorium is cut into two pieces, only one of which contains the nucleus, this one alone grows into a complete nucleated cell; the unnucleated portion dies, being unable to regenerate itself.

In the multicellular body of the tissue-forming organisms we must distinguish between the partial death of the various cells and the total death of the whole organism, or cell-state, which they make up. In many of the lower tissue-plants and tissue-animals the communal link is very loose and the centralization slight. Odd cells or groups of cells may be set loose, without any danger to the life of the whole histon, and grow into new individuals. In many of the algÆ and liverworts (even in the bryophyllum, closely related to the stone-crop, or sedum)—as well as in the common fresh-water polyp, hydra, and other polyps—every bit that is cut off is capable of growing into a complete individual. But the higher the organization is developed and the closer the correlation of the parts and their co-operation in the life of the centralized stock or person, the slighter we find the regenerative faculty of the several organs. Even then, however, many used-up cells may be removed and replaced by regenerated new cells. In our own human organism, as in that of the higher animals, thousands of cells die every day, and are replaced by new cells of the same kind, as, for instance, epidermic cells at the surface of the skin, the cells of the salivary glands or the mucous lining of the stomach, the blood-cells, and so on. On the other hand, there are tissues that have little or nothing of this repairing power, such as many of the nerve-cells, sense-cells, muscle-cells, etc. In these cases a number of constant cell-individuals remain with their nucleus throughout life, although a used-up portion of their cell-body may be replaced by regeneration from the cytoplasm. Thus our human body, like that of all the higher animals and plants, is a "cell-state" in another sense. Every day, nay, every hour, thousands of its citizens, the tissue-cells, pass away, and are replaced by others that have arisen by cleavage of similar cells. Nevertheless, this uninterrupted change of our personality is never complete or general. There is always a solid groundwork of conservative cells, the descendants of which secure the further regeneration.

Most organisms meet their death through external or accidental causes—lack of sufficient food, isolation from their necessary environment, parasites and other enemies, accidents and disease. The few individuals who escape these accidental causes of death find the end of life in old age or senility, by the gradual decay of the organs and dwindling of their functions. The cause of this senility and the ensuing natural death is determined for each species of organisms by the specific nature of their plasm. As Kassowitz has lately pointed out, the senility of individuals consists in the inevitable increase in the decay of protoplasm and the metaplastic parts of the body which this produces. Each metaplasm in the body favors the inactive break-up of protoplasm, and so also the formation of new metaplasms. The death of the cells follows, because the chemical energy of the plasm gradually falls off from a certain height, the acme, of life. The plasm loses more and more the power to replace by regeneration the losses it sustains by the vital functions. As, in the mental life, the receptivity of the brain and the acuteness of the senses gradually decay, so the muscles lose their energy, the bones become fragile, the skin dry and withered, the elasticity and endurance of the movements decrease. All these normal processes of senile decay are caused by chemical changes in the plasm, in which dissimilation gains constantly on assimilation. In the end they inevitably lead to normal death.

While the gradual decay of the bodily forces and the senile degeneration of the organs must necessarily cause the death of the soundest organism in the end, the great majority of men pass away through illness long before this normal term of life is reached. The external causes of this are the attacks of enemies and parasites, accidents, and unfavorable conditions of life. These cause changes in the tissues and their component cells, which first occasion the partial death of particular sections, and then the total death of the whole individual. The modifications of the living matter which produce disease and premature death are called necrobioses. They consist partly of histolyses—that is to say, degeneration of the cells by atrophy, dissolution, withering (mortification), or colliquation; and partly of metaplasmosisms, or metamorphoses of the plasm—fatty, mucous, chalky, or amyloid metamorphoses of the cells. It was the great merit of Rudolph Virchow that he proved, in his epoch-making Cellular Pathology (1858), that all diseases in man and other organisms may be reduced to such modifications of the cells which make up the tissues. Hence disease, with its pain, is a physiological process, a life under injurious and dangerous conditions. As in all normal vital phenomena, so in abnormal or pathological, the ultimate ground must be sought in the physical and chemical processes in the plasm. Pathology is a part of physiology. This discovery has cut the ground from under the older notion of disease as a special entity, a devil, or a divine punishment.

The natural physical explanation of death, which has been made possible by modern physiology and pathology, has shattered, not only all the old superstitious ideas about disease and death, but also a number of important metaphysical dogmas which built upon them. Such was, for instance, the naÏve belief in a conscious Providence, controlling the fate of individuals and determining their death. I do not fail to appreciate the great subjective value which such a trust in a protecting Providence has for men amid their countless dangers. We may envy the childish temper for the confidence and hope which it derives from this belief. But as we do not seek to have our emotions gratified by poetic fictions, we are bound to point out that reason cannot detect the shadow of a proof of the existence and action of this conscious Providence, or "loving Father in heaven." We read daily in our journals of accidents and crimes of all kinds that cause the unexpected death of happy human beings. Every year we read with horror the statistics of the thousands of deaths from shipwreck and railway accidents, earthquakes and landslips, wars and epidemics. And then we are asked to believe in a loving Providence that has decreed the death of each of these poor mortals! We are asked to console ourselves in face of the tragedy with the hollow phrases: "God's will be done," or "God's ways are wonderful." Simple children and dull believers may soothe themselves with such phrases. They no longer impose on educated people in the twentieth century, who prefer a full and fearless knowledge of the truth.

When our monistic and rational conception of death is described as dreary and hopeless, we may answer that the prevalent dualistic view is merely an outcome of hereditary habits of thought and mystic training in early youth. When these are displaced by progressive culture and science, it will be clear that man has lost nothing, but gained much, as regards his life on earth. Convinced that there is no eternal life awaiting him, he will strive all the more to brighten his life on earth and rationally improve his condition in harmony with that of his fellows. If it is objected that then everything will depend on mere "chance," instead of being controlled by a conscious Providence or a moral order of the world, I must refer the reader for my reply to the close of the fourteenth chapter of the Riddle, where I have dealt with fate, providence, end, aim, and chance. And if it is further claimed that our realistic view of life leads to pessimism, there is no better ground for such an accusation.

I have given, in the eleventh chapter of the Riddle, the scientific reasons which forbid us to accept the personal immortality of the soul. But as the most vehement attacks have been made on this chapter by metaphysicians of the prevailing school and by Christian theologians, I must return to the question here. I am convinced, from numbers of letters I have received and conversation with educated people of all classes, that no other dogma is so firmly established and highly valued as athanatism, or the belief in personal immortality. Most men will not give up at any price the hope that a better life awaits them beyond the grave, which will compensate them for all the pain and suffering they endure here. In the picturing of this future life the mediÆval geocentric idea still forms the chief feature. Troelslund has shown, in his Idea of Heaven and of the World, how this theory still dominates the metaphysics of the majority of men; in spite of Copernicus and Laplace, heaven is still for most people the semicircular blue glass bell that overarches the earth. We still hear the praises of our life in this heaven sung daily in sermons and speeches and festive orations. The orator extends his right hand "upward" to the infinite starry space of heaven, forgetting that the radius of the direction he is pointing towards changes every second, and in twelve hours reaches the precisely opposite direction, and becomes "downward." Other believers endeavor to be still more concrete, and point out definite celestial bodies as the homes of immortal souls. Modern cosmology, astronomy, and geology entirely exclude these pretty fictions from science; and modern psychology, physiology, ontogeny, and phylogeny rigorously refuse an inch of ground for athanatism.

Optimism regards the world on its good and bright and admirable side: pessimism looks to the shades and tragedies of life. In some philosophic and religious systems one or other of these tendencies is consistently and exclusively worked out; but in most systems the two are mingled. Pure and consistent realism is generally neither optimistic nor pessimistic. It takes the world as it is, a unified whole, the nature of which is neither good nor bad. Dualistic idealism, however, generally combines the two, and distributes them between its two worlds; it describes this world as a "vale of tears," and the next as a glorious city of joy and happiness. This view is a conspicuous feature in most of the dualistic religions, and has still a considerable influence, both practically and theoretically, on the minds of educated people.

The founder of systematic optimism was Gottfried Leibnitz, whose philosophy sought to achieve an ingenious harmony between divergent systems, but is really a form of dynamism, or a monism somewhat akin to the energism of Ostwald. Leibnitz gave a compendious statement of his system in his Monadology (1714). He taught that the world consists of an infinite number of monads (which almost correspond to our psychic atoms), but this pluralism was converted into a monism by making God, as the central monad, bind all together in a substantial unity. In his Theodicy (1710) he taught that God (the "all-wise, all-good, and almighty creator of the world") had with perfect consciousness created "the best of all possible worlds"; that his infinite goodness, wisdom, and power are seen everywhere in the pre-established harmony of things; but that the individual human being, and humanity taken as a whole, have only a limited capacity for development. The man who knows the real features of the world, who has honestly confronted the tragic struggle for life that rules throughout living nature, who has sympathy for the infinite sum of misery and want of every kind in the life of men, can scarcely understand how an acute and informed thinker like Leibnitz could entertain such optimism as this. It would be more intelligible in the case of a one-sided and nebulous metaphysician like Hegel, who held that "all that is real is rational and all that is rational is real."

Pessimism is the direct opposite of systematic optimism. While the one holds the universe to be the best, the other regards it as the worst, of all possible worlds. This pessimistic conception has found expression in the oldest and most popular religions of Asia, Brahmanism and Buddhism. Both these Hindoo religions were originally pessimistic, and at the same time atheistic and idealistic. Schopenhauer especially pointed out this, declaring that they were the most perfect of all religions, and importing their leading ideas into his own system. He considers it "a glaring absurdity to attempt to prove this miserable world the best of all possible ones—this cock-pit of tortured and suffering beings, who can only survive by destroying one another, in which the capacity for pain grows with knowledge, and so reaches its height in man. Truly optimism cuts so sorry a figure in this theatre of sin, suffering, and death that we should have to regard it as a piece of sarcasm if Hume had not given us an explanation of its origin (the wish to flatter God and hope for some result from it). To the palpable sophistry of Leibnitz, who would prove this world the best of all possible, we can oppose a strict and honest proof that it is the worst of all possible." However, neither Schopenhauer nor the most important of modern pessimists, Edward Hartmann, has drawn the strict practical conclusion from pessimism. That would be to deny the will to live, and put an end to suffering by suicide.

The mention of suicide as the logical consequence of pessimism may serve as an occasion to glance at the curious and contradictory views that are expressed about it. There are few problems of life (apart from immortality and the freedom of the will) on which such absurd and contradictory things have been said even down to our own time. The theist who regards life as a gift of God may hesitate to reject or return it—although the offering of one's self as a victim for other men is considered a high virtue. Most educated people still look upon suicide as a great sin, and in some countries (such as England) the attempt is punished by law. In the Middle Ages, when a hundred thousand men were burned alive for heresy or witchcraft, suicides were punished by a disgraceful burial. As Schopenhauer says: "Clearly there is nothing in the world to which a man has a plainer right than his own life and person. It is simply ridiculous for criminal justice to deal with suicide." The advance of embryology in the last thirty years has made it clear that the individual life of a man (and all other vertebrates) begins at the moment when the male sperm-cell and the maternal ovum coalesce. In this blind chance plays an important part, as in so many other important aspects of life—taking "chance" in the scientific sense, which I have explained in chapter xiv. of the Riddle. Hence, the real cause of personal existence is not the favor of the Almighty, but the sexual love of one's earthly parents; very often this consequence of the act of love has been anything but desired. If, then, the circumstances of life come to press too hard on the poor being who has thus developed, without any fault of his, from the fertilized ovum—if, instead of the hoped-for good, there come only care and need, sickness and misery of every kind—he has the unquestionable right to put an end to his sufferings by death. Every religion assents to this under certain conditions, even Christianity when it says: "If thine eye scandalize thee, cast it from thee." It is true that the conventional morality condemns suicide under any circumstances; but the reasons it alleges are ridiculously slight, and are not improved by having the mantle of religion wrapped about them.

The voluntary death by which a man puts an end to intolerable suffering is really an act of redemption. We should, therefore, describe it as self-redemption, and look on it with Christian sympathy, not brand it pharisaically as "self-murder." As a fact, this contemptuous phrase has no meaning, since murder is the taking away of a man's life against his will, while the suicide dies voluntarily. Hence, he usually deserves our sympathy, not contempt, and certainly not punishment. Our conventional morality is, as so often happens, full of senseless contradictions. Modern states have introduced conscription; they demand that every citizen shall give up his life for his country on command, and kill as many other men as he can (an admirable commentary on the Scriptural "Love your enemies") for some political reason or other. But they never secure to each citizen the means of honorable existence and free development of his personality—not even the right to work by which he may maintain himself and his family.

I fully recognize the advance that social politics has made in improving the conditions of the poorer classes, the promotion of hygiene and education and the bodily and mental welfare of citizens; but we are still very far from the attainable ideal of general prosperity and happiness which reason dictates to every civilized nation. Misery and want are increasing among the poor, as the division of labor and over-population increase. Thousands of strong and active men come to grief every year without any fault of theirs, often precisely because they were quiet and honest; thousands are hungry because, with the best will in the world, they cannot find work; thousands are sacrificed to the heartless demands of our iron age of machinery with its exacting technical and industrial requirements. On the other hand, we see thousands of contemptible characters prospering because they have been able to deceive their fellows by unscrupulous speculations, or because they have flattered and served the higher authorities. It is no wonder that the statistics of suicide increase so much in the more civilized communities. No feeling man who has any real "Christian love of his neighbor" will grudge his suffering brother the eternal rest and the freedom from pain which he has obtained by his self-redemption.

The seventh petition of the Lord's Prayer, which is repeated daily by millions of Christians, is: "Deliver us from evil." Luther explains this as a prayer to be saved "from all evil of body and soul" in this life and the next. When we consider this in the light of our monistic principles, we have naturally to set aside the superstitious ideas of the Middle Ages regarding the future life, and deal only with the petition as regards this life. The number and variety and gravity of these evils have grown in civilized communities in the nineteenth century, notwithstanding all the progress we have made in art and science and the rational reform of our personal and social life. Civilization has gained infinitely in value by the change we have made in our conceptions of time and space in this age of steam and electricity. We can make our domestic and public life much pleasanter, and avail ourselves of a far greater number of luxuries, than was possible to our grandfathers a hundred years ago. But all this has caused a much greater expenditure of nerve-energy. The brain has to bear a much greater strain, and is worn out earlier, the body is more stimulated and overworked than it was a hundred years ago. Many diseases of modern civilization are making appalling progress; neurasthenia, especially, and other diseases of the nerves, carry off more victims every year. Our asylums grow bigger and more numerous every year, and we have sanatoria on every side in which the baited victim of modern civilization seeks refuge from his evils. Some of these evils are quite incurable, and the sufferers have to meet a certain death in terrible pain. Many of these poor creatures look forward to their redemption from evil and the end of their miserable lives. The important question arises whether, as compassionate men, we should be justified in carrying out their wish and ending their sufferings by a painless death.

This question is of great importance, both in practical philosophy and in juridical and medical practice, and, as opinions differ very much on the subject, it seems advisable to deal with it here. I start from my own personal opinion, that sympathy is not only one of the noblest and finest functions of the human brain, but also one of the first conditions of the social life of the higher animals. The precepts of Christian charity which the gospels rightly place in the very foreground of morality, were not first discovered by Christ, but they were successfully urged by him and his followers at a time when refined selfishness threatened the Roman civilization with decay. These natural principles of sympathy and altruism had arisen thousands of years before in human society, and are even found among all the higher animals that live a social life. They have their first roots in the sexual reproduction of the lower animals, the sexual love and the care of the young on which the maintenance of the species depends. Hence the modern prophets of pure egoism, Friedrich Nietzsche, Max Stirner, etc., commit a biological error when they would substitute their morality of the strong for universal charity, and when they ridicule sympathy as a weakness of character or an ethical blunder of Christianity. It is just in its insistence on sympathy that the Christian teaching is most valuable, and this part of its system will survive long after its dogmas have sunk into oblivion. However, this lofty duty must not be confined to men, but extended to "our relations," the higher vertebrates, and, in fact, to all animals whose brain-organization seems to point to the possession of sensation and a consciousness of pleasure and pain. Thus, for instance, in the case of the domestic animals which we use daily in our service, and which have an undoubted psychic affinity to ourselves, we must take care to increase their pleasures and mitigate their sufferings. Faithful dogs and noble horses, with which we have lived for years and which we love, are rightly put to death and relieved from pain when they fall hopelessly ill in old age. In the same way we have the right, if not the duty, to put an end to the sufferings of our fellow-men. Some severe and incurable disease makes life unbearable for them, and they ask for redemption from evil. However, medical men hold very different opinions on the matter, as I have found in conversation with them. Many experienced physicians, who practise their profession in a spirit of sympathy and without dogmatic prejudice, have no scruple about cutting short the sufferings of the incurable by a dose of morphia or cyanide of potassium when they desire it; very often this painless end is a blessing both to the invalids and their families. However, other physicians and most jurists are of opinion that this act of sympathy is not right, or is even a crime; that it is the duty of the physician to maintain the life of his patients as long as he can in all circumstances. I should like to know why.

While I am dealing with this important and—for the medical conscience—difficult question of social ethics, I may take the opportunity to consider the general attitude of physicians to the monistic philosophy. It is now half a century since I visited the wards in the Julius hospital at WÜrtzburg as a medical student. It is true that—happily for me and my patients!—I practised the profession only for a short time after I had passed my examinations in 1857; but the thorough acquaintance with the human organism, its anatomic structure and physiological functions, which I then obtained has been of incalculable service to me. I owe to it not only the solid empirical foundation of the special study of my life, zoology, but also the monistic tendency of my whole system. As the medical training in its widest sense includes anthropology—and so should include psychology also—its value for speculative philosophy cannot be exaggerated. The scholastic metaphysicians who still regard the chairs of philosophy at our universities as their monopoly would have avoided most of their dualistic errors if they had had a thorough training in human anatomy, physiology, ontogeny, and phylogeny. Even pathology, the science of the diseased organism, is very instructive for the philosopher. The psychologist especially acquires, by the study of mental disease and the visiting of the asylum wards, a profound insight into the mental life which no speculative philosophy could give him. There are few experienced and thoughtful physicians who retain the conventional belief in the immortality of the soul and God. What would the immortal soul do on the other side of eternity when it is already utterly ruined in this life, or was even born as an idiot? How can a just God condemn the criminal to the fires of hell when he himself has tainted the man with an hereditary bias, or has placed him in an environment in which, seeing the absence of free-will, crime was a necessity for him? And how can this all-loving God answer for the immeasurable sum of want and misery, and pain and unhappiness, which he sees accumulated before him every year in the lives of families and states, cities and hospitals? It is no wonder that the old saying ran: Ubi tres medici, duo sunt athei (Of three doctors two are sure to be atheists). One of my medical colleagues was an old, experienced, and sympathetic physician who had travelled all over the world, and had then, as director of a large hospital, been a close witness of the sufferings of humanity. Religiously educated by pious parents, and endowed with keen sensitiveness, he was, after long struggles, forced by his medical studies to part with the faith of his boyhood—like myself, in his twenty-first year. We were talking about the great mysteries of life shortly before his death, and he said to me: "I have been unable to reconcile belief in the immortality of the soul and the freedom of the will with my psychological experiences, and I have been just as unable to discover throughout the whole world a single trace of a moral order or a beneficent providence. If it is true that an intelligent Deity rules the world, he cannot be a God of love, but an all-powerful demon, whose constant entertainment is an eternal and merciless play of being and becoming, building up and destroying." However, we do still find here and there informed and intelligent physicians who adhere to the three central dogmas of metaphysics—a proof of the immense power of dogmatic tradition and religious prejudice.

We must class as a traditional dogma the wide-spread belief that man is bound under all circumstances to maintain and prolong life, even when it has become utterly useless—a source of pain to the incurable and of endless trouble to his friends. Hundreds of thousands of incurables—lunatics, lepers, people with cancer, etc.—are artificially kept alive in our modern communities, and their sufferings are carefully prolonged, without the slightest profit to themselves or the general body. We have a strong proof of this in the statistics of lunacy and the growth of asylums and nerve-sanatoria. In Prussia alone there were 51,048 lunatics cared for in the asylums (six thousand in Berlin) in 1890; more than one-tenth of them were quite incurable (four thousand of them suffering from paralysis). In France, in 1871, there were 49,589 in the asylums (or 13.8 per thousand of the population), and in 1888 there were 70,443 (or 18.2 per thousand); thus, in the course of seventeen years, the absolute number of the unsound rose nearly 30 per cent. (29.6), while the total population only increased 5.6 per cent. In our day the number of lunatics in civilized countries is, on the average, five-sixths per thousand. If the total population of Europe is put at three hundred and ninety to four hundred millions, we have at least two million lunatics among them, and of these more than two hundred thousand are incurable. What an enormous mass of suffering these figures indicate for the invalids themselves, and what a vast amount of trouble and sorrow for their families, what a huge private and public expenditure! How much of this pain and expense could be spared if people could make up their minds to free the incurable from their indescribable torments by a dose of morphia! Naturally this act of kindness should not be left to the discretion of an individual physician, but be determined by a commission of competent and conscientious medical men. So, in the case of other incurables and great sufferers (from cancer, for instance), the "redemption from evil" should only be accomplished by a dose of some painless and rapid poison when they have expressed a deliberate wish (to be afterwards juridically proved) for this, and under the control of an authoritative commission.

The ancient Spartans owed a good deal of their famous bravery, their bodily strength and beauty, as well as their mental energy and capacity, to the old custom of doing away with new-born children who were born weakly or crippled. We find the same custom to-day among many savage races. When I pointed out the advantages of this Spartan selection for the improvement of the race in 1868 (chapter vii. of the History of Creation) there was a storm of pious indignation in the religious journals, as always happens when pure reason ventures to oppose the current prejudices and traditional beliefs. But I ask: What good does it do to humanity to maintain artificially and rear the thousands of cripples, deaf-mutes, idiots, etc., who are born every year with an hereditary burden of incurable disease? Is it not better and more rational to cut off from the first this unavoidable misery which their poor lives will bring to themselves and their families? It is no use to reply that religion forbids it. Christianity also bids us give up our life for our brethren, and to cast it from us when it hurts us—that is to say, when it only causes useless pain to us and our friends. The truth is, the opposition is only due to sentiment and the power of conventional morality—that is to say, to the hereditary bias which is clothed in early youth with the mantle of religion, however irrational and superstitious be its foundation. Pious morality of this sort is often really the deepest immorality. "Laws and rights creep on like an eternal sickness;" this is equally true of the social customs and morals on which laws and rights are founded. Sentiment should never be allowed to usurp the place of reason in these weighty ethical questions. As I pointed out in the first chapter of the Riddle, sentiment is a very amiable, but a very dangerous, function of the brain. It has no more to do with the attainment of the truth than what is called revelation. That is well seen in Kant's dualism, for his mundus intelligibilis is essentially an outcome of his religious sentimentality

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