Now we shall find that these indispensable preliminary conditions are, unfortunately, by no means fulfilled by the majority of naturalists of the present day. The immense amount of empirical facts with which the gigantic advances of modern natural science have recently made us acquainted has led to a prevailing inclination for the special study of single phenomena and of small and narrow domains. This causes the knowledge of other paths, and especially of Nature as a great comprehensive whole, to be in most cases completely neglected. Every one with sound eyes and a microscope, together with industry and patience for study, can in our day attain a certain degree of celebrity by microscopic "discoveries," without, however, deserving the name of a naturalist. This name is deserved only by him who not merely strives to _know_ the individual phenomena, but who also seeks to _discover_ their causal connection. Even in our own day, most palaeontologists examine and describe fossils without knowing the most important facts of embryology.

Embryologists, on the other hand, follow the history of development of a particular organic individual, without having an idea of the palaeontological history of the whole tribe, of which fossils are the records. And yet these two branches of the organic history of development-ontogeny, or the history of the individual, and phylogeny, or the history of the tribe-stand in the closest causal connection, and the one cannot be understood without the other. The same may be said of the systematic and the anatomical part of Biology. There are even now, in zoology and botany, many systematic naturalists who work with the erroneous idea that it is possible to construct a natural system of animals and plants simply by a careful examination of the external and readily accessible forms of bodies, without a deeper knowledge of their internal structure. On the other hand, there are anatomists and histologists who think it possible to obtain a true knowledge of animal and vegetable bodies merely by a most careful examination of the inner structure of the body of some individual species, without the comparative examination of the bodily form of all kindred organisms. And yet here, as everywhere, the internal and external factors, to wit, Inheritance and Adaptation, stand in the closest mutual relation, and the individual can never be thoroughly understood without a comparison of it with the whole of which it is a part. To those one-sided specialists we should like in Goethe's words to say:-

We must, contemplating Nature, Part as Whole, give equal heed to: Nought is inward, nought is outward, For the inner is the outer.[6]

And again:-

Nature has neither kernel nor sh.e.l.l, It is she that is All and All at once.[7]

What is even more detrimental to the general understanding of nature as a whole than this one-sided tendency, is _the want of a philosophical culture_, and this applies to most of the naturalists of the present day. The various errors of the earlier speculative nature-philosophy made during the first thirty years of our century, have brought the whole of philosophy into such bad repute with the exact empirical naturalists, that they live in the strange delusion that it is possible to erect the edifice of natural science out of mere facts, without their philosophic connection; in short, out of mere knowledge, without the understanding of it. But as a purely speculative and absolutely philosophical system, which does not concern itself with the indispensable foundation of empirical facts, becomes a castle in the air, which the first real experiment throws to the winds; so, on the other hand, a purely empirical system, constructed of nothing but facts, remains a disorderly heap of stones, which will never deserve the name of an edifice. Bare facts established by experience are nothing but rude stones, and without their thoughtful valuation, without their philosophic connection, no science can be established. As I have already tried to impress upon my reader, the _strong edifice of true monistic science_, or what is the same thing, the _Science of Nature, exists only by the closest interaction, and the reciprocal penetration of philosophy and empirical knowledge_.

This lamentable estrangement between science and philosophy, and the rude empiricism which is now-a-days unfortunately praised by most naturalists as "exact science," have given rise to those strange freaks of the understanding, to those gross insults against elementary logic, and to that incapacity for forming the simplest conclusions which one may meet with any day in all branches of science, but especially in zoology and botany. It is here that the neglect of a philosophical culture and training of the mind, directly avenges itself most painfully. It is not to be wondered at that the deep inner truth of the Theory of Descent remains a sealed book to those rude empiricists. As the common proverb justly says: they cannot see the wood for the trees.

It is only by a more general philosophical study, and especially by a more strictly logical training of the mind, that this sad state of things can be remedied. (Compare Gen. Morph. i. 63; ii. p. 447.)

If we rightly consider this circ.u.mstance, and if we further reflect upon it in connection with the empirical foundation of the philosophical theory of development, we shall at once see how we are placed respecting the oft-demanded _proofs of the theory of descent_. The more the doctrine of filiation has of late years made way for itself, and the more all thoughtful, younger naturalists, and all truly biologically-educated philosophers have become convinced of its inner truth and absolute necessity, the louder have its opponents called for actual proofs. The same persons who, shortly after the publication of Darwin's work, declared it to be "a groundless, fantastic system," an "arbitrary speculation," an "ingenious dream," now kindly condescend to declare that the theory of descent certainly is a scientific "_hypothesis_," but that it still requires to be "_proved_." When these remarks are made by persons who do not possess the requisite empirico-philosophical culture, nor the necessary knowledge in comparative anatomy, embryology, and palaeontology, we cannot be much offended, and we refer them to the study of those sciences. But when similar remarks are made by acknowledged specialists, by teachers of zoology and botany, who certainly ought to possess a general insight into the whole domain of their science, or who are actually familiar with the facts of those scientific domains, then we are really at a loss what to say. Those who are not satisfied with the treasures of our present empirical knowledge of nature as a basis on which to establish the Theory of Descent, will not be convinced by any other facts which may hereafter be discovered; for we can conceive no circ.u.mstances which would furnish stronger or a more complete testimony to the truth of the doctrine of filiation than is even now seen, for example, in the well-known facts of comparative anatomy and ontogeny. I must here again direct attention to the fact, _that all the great and general laws, and all the comprehensive series of phenomena of the most different domains of biology can only be explained and understood by the Theory of Development_ (and especially by its biological part, the Theory of Descent), and that without it they remain completely inexplicable and incomprehensible. _The internal causal connection_ between them all proves the Theory of Descent to be the greatest _inductive law_ of Biology.

Before concluding, I will once more name all those series of inductions, all those general laws of Biology, upon which this comprehensive law of development is firmly based.

(1.) _The palaeontological history of the development of organisms_, the gradual appearance and the historical succession of the different species and groups of species, the empirical laws of the palaeontological change of species, as furnished to us by the science of fossils, and more especially the _progressive differentiation and perfecting_ of animal and vegetable groups in the successive periods of the earth's history.

(2.) _The individual history of development of organisms_, embryology and metamorphology, the gradual changes in the slow development of the body and its particular organs, especially _the progressive differentiation and perfecting_ of the organs and parts of the body in the successive periods of the individual development.

(3.) _The inner causal connection between ontogeny and phylogeny_, the parallelism between the individual history of the development of organisms, and the palaeontological history of the development of their ancestors, a connection which is actually established by the laws of _Inheritance_ and _Adaptation_, and which may be summed up in the words: ontogeny, according to the laws of inheritance and adaptation, repeats in its large features the outlines of phylogeny.

(4.) _The comparative anatomy of organisms_, the proof of the essential agreement of the inner structure of kindred organisms, in spite even of the greatest difference of external form in the various species; their explanation by the causal dependence of the internal agreement of the structure on _Inheritance_, the external dissimilarity of the bodily form on _Adaptation_.

(5.) _The inner causal connection between comparative anatomy and the history of development_, the harmonious agreement between the laws of the gradual development, _the progressive differentiation and perfecting_, as they may be seen in comparative anatomy on the one hand, in ontogeny and palaeontology on the other.

(6.) _Dysteleology, or the theory of purposelessness_, the name I have given to the _science of rudimentary organs_, of suppressed and degenerated, aimless and inactive, parts of the body; one of the most important and most interesting branches of comparative anatomy, which, when rightly estimated, is alone sufficient to refute the fundamental error of the teleological and dualistic conception of Nature, and to serve as the foundation of the mechanical and monistic conception of the universe.

(7.) _The natural system of organisms_, the natural grouping of all the different forms of Animals, Plants, and Protista into numerous smaller or larger groups, arranged beside and above one another; the kindred connection of species, genera, families, orders, cla.s.ses, tribes, etc., more especially, however, the _arboriform branching character of the natural system_, which is the spontaneous result of a natural arrangement and cla.s.sification of all these graduated groups or categories. The result attained in attempting to exhibit the relationships of the mere forms of organisms by a tabular cla.s.sification is only explicable when regarded as the expression of their actual _blood relationship_; _the tree shape of the natural system_ can only be understood as the actual _pedigree of the organisms_.

(8.) _The chorology of organisms_, the science of the local distribution of organic species, of their _geographical_ and _topographical dispersion over the surface of the earth_, over the heights of mountains and in the depths of the ocean, but especially the important phenomenon that every species of organism proceeds from a so-called "_centre of creation_" (more correctly a "_primaeval home_" or "_centre of distribution_"); that is, from a single locality, where it originated but once, and whence it spread.

(9.) _The cology of organisms_, the knowledge of the sum of the _relations of organisms to the surrounding outer world_, to organic and inorganic conditions of existence; the so-called "_economy of nature_,"

the correlations between all organisms living together in one and the same locality, their adaptation to their surroundings, their modification in the struggle for existence, especially the circ.u.mstances of parasitism, etc. It is just these phenomena in "the economy of nature" which the unscientific, on a superficial consideration, are wont to regard as the wise arrangements of a Creator acting for a definite purpose, but which on a more attentive examination show themselves to be the necessary results of mechanical causes.

(10.) _The unity of Biology as a whole_, the deep inner connection existing between all the phenomena named and all the other phenomena belonging to zoology, protistics, and botany, and which are simply and naturally explained by a single common principle. This principle can be no other than the common derivation of all the specifically different organisms from a single, or from several absolutely simple, primary forms like the Monera, which possess no organs. The Theory of Descent, by a.s.suming this common derivation, throws a clear light upon these individual series of phenomena, as well as upon their totality, without which their deeper causal connection would remain completely incomprehensible to us. The opponents of the Theory of Descent can in no way explain any single one of these series of phenomena or their deeper connection with one another. So long as they are unable to do this, _the Theory of Descent remains the one adequate biological theory_.

We should, on account of the grand proofs just enumerated, have to adopt Lamarck's Theory of Descent for the explanation of biological phenomena, even if we did not possess Darwin's Theory of Selection. The one is so completely and _directly proved_ by the other, and established by mechanical causes, that there remains nothing to be desired. The laws of _Inheritance_ and _Adaptation_ are universally acknowledged _physiological_ facts, the former traceable to _propagation_, the latter to the _nutrition_ of organisms. On the other hand, the _struggle for existence_ is a _biological_ fact, which with mathematical necessity follows from the general disproportion between the average number of organic individuals and the numerical excess of their germs. But as Adaptation and Inheritance in the struggle for life are in continual interaction, it inevitably follows that _natural selection_, which everywhere influences and continually changes organic species, must, by making use of _divergence of character_, produce new species. Its influence is further especially favoured by the active and pa.s.sive _migrations_ of organisms, which go on everywhere. If we give these circ.u.mstances due consideration, the continual and gradual modification or trans.m.u.tation of organic species will appear as a biological process, which must, according to causal law, of _necessity_ follow from the actual nature of organisms and their mutual correlations.

That even the _origin of man_ must be explained by this general organic process of trans.m.u.tation, and that it is simply as well as naturally explained by it, has, I believe, been sufficiently proved in my last chapter but one. I cannot, however, avoid here once more directing attention to the inseparable connection between this so-called "theory of apes," or "pithecoid theory," and the whole Theory of Descent. If the latter is the greatest _inductive law_ of biology, then it of necessity follows that the former is its most important _deductive law_. They stand and fall together. As all depends upon a right understanding of this proposition, which in my opinion is very important, and which I have therefore several times brought before the reader, I may be allowed to explain it here by an example.

In all mammals known to us the centre of the nervous system is the spinal marrow and the brain, and the centre of the vascular system is a quadrupal heart, consisting of two princ.i.p.al chambers and two ante-chambers. From this we draw the general inductive conclusion that all mammals, without exception, those extinct, together with all those living species as yet unknown to us, as well as the species which we have examined, possess a like organization, a like heart, brain, and spinal marrow. Now if, as still happens every year, there be discovered in any part of the earth a new species of mammal, a new species of marsupial, or a new species of deer, or a new species of ape, every zoologist knows with certainty at once, without having examined its inner structure, that this species must possess a quadruple heart, a brain and spinal marrow, like all other mammals. Not a single naturalist would ever think of supposing that the central nervous system of this new species of mammal could possibly consist of a ventral cord with an sophageal collar as in the insects, or of scattered pairs of knots as in the molluscs, or that its heart could be many-chambered as in flies, or one-chambered as in the tunicates. This completely certain and safe conclusion, although it is not based upon any direct experience, is a _deductive conclusion_. In the same way, as I have shown in a previous chapter, Goethe, from the comparative anatomy of mammals, established the general inductive conclusion that they all possess a mid jawbone, and afterwards drew from it the special deductive conclusion that man, who in all other respects does not essentially differ from other mammals, must also possess a like mid jawbone. He maintained this conclusion without having actually seen the human mid jawbone, and only proved its existence subsequently by actual observation (vol. i. p. 84).

The process of _induction_ is a logical system of forming conclusions _from the special to the general_, by which we advance from many individual experiences to a general law; _deduction_, on the other hand, draws a conclusion _from the general to the special_, from a general law of nature to an individual case. Thus the _Theory of Descent_ is, without doubt, a great _inductive law_, empirically based upon all the biological experience cited above; the pithecoid theory, on the other hand, which a.s.serts that man has developed out of lower, and in the first place out of ape-like mammals, is a _deductive law_ inseparably connected with the general inductive law.

The pedigree of the human race, the approximate outlines of which I gave in the last chapter but one, of course remains in detail (like all the pedigrees of animals and plants previously discussed) a more or less approximate general hypothesis. This however does not affect the application of the theory of descent to man. Here, as in all investigations on the derivation of organisms, one must clearly distinguish between the general _theory_ of descent and the special _hypotheses_ of descent. The general _theory_ of descent claims full and lasting value, because it is an inductive law, based upon all the whole series of biological phenomena and their inner causal connection. Every special _hypothesis_ of descent, on the other hand, has its special value determined by the existing condition of our biological knowledge, and by the extent of the objective empirical basis upon which we deductively establish this particular hypothesis. Hence, all the individual attempts to obtain a knowledge of the pedigree of any one group of organisms possesses but a temporary and conditional value, and any special hypothesis relating to it will become the more and more perfect the greater the advance we make in the comparative anatomy, ontogeny, and palaeontology of the group in question. The more, however, we enter into genealogical details, and the further we trace the separate off-shoots and branches of the pedigree, the more uncertain and subjective becomes our special _hypothesis_ of descent on account of the incompleteness of our empirical basis. This however does no injury to the general _theory_ of descent, which remains as the indispensable foundation for really profound apprehension of biological phenomena.

Accordingly, there can be no doubt that we can and must, with full a.s.surance, regard the derivation of man-in the first place, from ape-like forms; farther back, from lower mammals, and thus continually farther back to lower stages of the vertebrata down to their lowest invertebrate roots, nay, even down to a simple plastid-as a general _theory_. On the other hand, the special tracing of the human pedigree, the closer definition of the animal forms known to us, which either actually belong to the ancestors of man, or at least stand in very close blood relationship to them, will always remain a more or less approximate _hypothesis_ of descent, all the more in danger of deviating from the real pedigree the nearer it endeavours to approach it by searching for the individual ancestral forms. This state of things results from the immense gaps in our palaeontological knowledge, which can, under no circ.u.mstances, ever attain to even an approximate completeness.

A thoughtful consideration of this important circ.u.mstance at once furnishes the answer to a question which is commonly raised in discussing this subject, namely, the question of scientific _proofs for the animal origin of the human race_. Not only the opponents of the Theory of Descent, but even many of its adherents who are wanting in the requisite philosophical culture, look too much for "signs" and for special empirical advances in the science of nature. They await the sudden discovery of a human race with tails, or of a talking species of ape, or of other living or fossil transition forms between man and the ape, which shall fill the already narrow chasm between the two, and thus empirically "prove" the derivation of man from apes. Such special manifestations, were they ever so convincing and conclusive, would not furnish the proof desired. Unthinking persons, or those unacquainted with the series of biological phenomena, would still be able to maintain the objections to those special testimonies which they now maintain against our theory.

The absolute certainty of the Theory of Descent, even in its application to man, is built on a more solid foundation; and its true inner value can never be tested simply by reference to individual experience, but only by a philosophical comparison and estimation of the treasures of all our biological experiences. The inestimable importance of the Theory of Descent is surely based upon this, that the theory follows of necessity (as a general inductive law) from the comparative synthesis of all organic phenomena of nature, and more especially from the triple parallelism of comparative anatomy, of ontogeny, and phylogeny; and the pithecoid theory under all circ.u.mstances (apart from all special proofs) remains as a special deductive conclusion which must of necessity be drawn from the general inductive law of the Theory of Descent.

In my opinion, all depends upon a right understanding of this _philosophical foundation of the Theory of Descent_ and of the _pithecoid theory_ which is inseparable from it. Many persons will probably admit this, and yet at the same time maintain that all this applies only to the _bodily_, not to the _mental_ development of man.

Now, as we have hitherto been occupied only with the former, it is perhaps necessary here to cast a glance at the latter, in order to show that it is also subject to the great general law of development. In doing this it is above all necessary to recollect that body and mind can in fact never be considered as distinct, but rather that both sides of nature are inseparably connected, and stand in the closest interaction.

As even Goethe has clearly expressed it-"matter can never exist and act without mind, and mind never without matter." The artificial discord between mind and body, between force and matter, which was maintained by the erroneous dualistic and teleological philosophy of past times has been disposed of by the advances of natural science, and especially by the theory of development, and can no longer exist in face of the prevailing mechanical and monistic philosophy of our day. How human nature, and its position in regard to the rest of the universe, is to be conceived of according to the modern view, has been minutely discussed by Radenhausen in his "Isis,"(33) which is excellent and well worth perusal.

With regard to the origin of the human mind or the soul of man, we, in the first place, perceive that in every human individual it develops from the beginning, step by step and gradually, just like the body. In a newly born child we see that it possesses neither an independent consciousness, nor in fact clear ideas. These arise only gradually when, by means of sensuous experience, the phenomena of the outer world affect the central nervous system. But still the little child is wanting in all those differentiated emotions of the soul which the full-grown man acquires only by the long experience of years. From this graduated development of the human soul in every single individual we can, in accordance with the inner causal connection between ontogeny and phylogeny, directly infer the gradual development of the human soul in all mankind, and further, in the whole of the vertebrate tribe. In its inseparable connection with the body, the human soul or mind has also had to pa.s.s through all those gradual stages of development, all those various degrees of differentiation and perfecting, of which the hypothetical series of human ancestors sketched in a late chapter gives an approximate representation.

It is true that this conception generally greatly offends most persons on their first becoming acquainted with the Theory of Development, because more than all others it most strongly contradicts the traditional and mythological ideas, and the prejudices which have been held sacred for thousands of years. But like all other functions of organisms, the human soul must necessarily have historically developed, and the comparative or empirical study of animal psychology clearly shows that this development can only be conceived of as a gradual evolution from the soul of vertebrate animals, as a gradual differentiation and perfecting which, in the course of many thousands of years, has led to the glorious triumph of the human mind over its lower animal ancestral stages. Here, as everywhere, the only way to arrive at a knowledge of natural truth is to compare kindred phenomena, and investigate their development. Hence we must above all, as we did in the examination of the bodily development, compare the highest animal phenomena on the one hand with the lowest animal phenomena, and on the other with the lowest human phenomena. The final result of this comparison is this-that _between the most highly developed animal souls, and the lowest developed human souls, there exists only a small quant.i.tative, but no qualitative difference_, and that this difference is much less than the difference between the lowest and the highest human souls, or than the difference between the highest and the lowest animal souls.

In order to be convinced of this important result, it is above all things necessary to study and compare the mental life of wild savages and of children.(32) At the lowest stage of human mental development are the Australians, some tribes of the Polynesians, and the Bushmen, Hottentots, and some of the Negro tribes. Language, the chief characteristic of genuine men, has with them remained at the lowest stage of development, and hence also their formation of ideas has remained at a low stage. Many of these wild tribes have not even a name for animal, plant, colour, and such most simple ideas, whereas they have a word for every single, striking _form_ of animal and plant, and for every single sound or colour. Thus even the most simple abstractions are wanting. In many of these languages there are numerals only for one, two, and three: no Australian language counts beyond four. Very many wild tribes can count no further than ten or twenty, whereas some very clever dogs have been made to count up to forty and even beyond sixty.

And yet the faculty of appreciating number is the beginning of mathematics! Nothing, however, is perhaps more remarkable in this respect, than that some of the wildest tribes in southern Asia and eastern Africa have no trace whatever of the first foundations of all human civilization, of family life, and marriage. They live together in herds, like apes, generally climbing on trees and eating fruits; they do not know of fire, and use stones and clubs as weapons, just like the higher apes. All attempts to introduce civilization among these, and many of the other tribes of the lowest human species, have hitherto been of no avail; it is impossible to implant human culture where the requisite soil, namely, the perfecting of the brain, is wanting. Not one of these tribes has ever been enn.o.bled by civilization; it rather accelerates their extinction. They have barely risen above the lowest stage of transition from man-like apes to ape-like men, a stage which the progenitors of the higher human species had already pa.s.sed through thousands of years ago.(44)

Now consider, on the other hand, the highest stages of development of mental life in the higher vertebrate animals, especially birds and mammals. If, as is usually done, we divide the different emotions of the soul into three princ.i.p.al groups-sensation, will, and thought-we shall find in regard to every one of them, that the most highly developed birds and mammals are on a level with the lowest human beings, or even decidedly surpa.s.s them. The _will_ is as distinctly and strongly developed in higher animals as in men of character. In both cases it is never actually free, but always determined by a causal chain of ideas.

(Compare vol. i. p. 237.) In like manner, the different degrees of will, energy, and pa.s.sion are as variously graduated in higher animals as in man. The _affections_ of the higher animals are not less tender and warm than those of man. The fidelity and devotion of the dog, the maternal love of the lioness, the conjugal love and connubial fidelity of doves and love-birds are proverbial, and might serve as examples to many men.

If these virtues are to be called "instincts," then they deserve the same name in mankind. Lastly, with regard to _thought_, the comparative consideration of which doubtless presents the most difficulties, this much may with certainty be inferred-especially from an examination of the comparative psychology of cultivated domestic animals-that the processes of thinking, here follow the same laws as in ourselves.

Experiences everywhere form the foundation of conceptions, and lead to the recognition of the connection between cause and effect. In all cases, as in man, it is the path of induction and deduction which leads to the formation of conclusions. It is evident that in all these respects the most highly developed animals stand much nearer to man than to the lower animals, although they are also connected with the latter by a chain of gradual and intermediate stages. In Wundt's excellent "Lectures on the Human and Animal Soul,"(46) there are a number of proofs of this.

Now, if inst.i.tuting comparisons in both directions, we place the lowest and most ape-like men (the Austral Negroes, Bushmen, and Andamans, etc.), on the one hand, together with the most highly developed animals, for instance, with apes, dogs, and elephants, and on the other hand, with the most highly developed men-Aristotle, Newton, Spinoza, Kant, Lamarck, or Goethe-we can then no longer consider the a.s.sertion, that the mental life of the higher mammals has gradually developed up to that of man, as in any way exaggerated. If one must draw a sharp boundary between them, it has to be drawn between the most highly developed and civilized man on the one hand, and the rudest savages on the other, and the latter have to be cla.s.sed with the animals. This is, in fact, the opinion of many travellers, who have long watched the lowest human races in their native countries. Thus, for example, a great English traveller, who lived for a considerable time on the west coast of Africa, says: "I consider the negro to be a lower species of man, and cannot make up my mind to look upon him as 'a man and a brother,' for the gorilla would then also have to be admitted into the family." Even many Christian missionaries, who, after long years of fruitless endeavours to civilize these lowest races, have abandoned the attempt, express the same harsh judgment, and maintain that it would be easier to train the most intelligent domestic animals to a moral and civilized life, than these unreasoning brute-like men. For instance, the able Austrian missionary Morlang, who tried for many years without the slightest success to civilize the ape-like negro tribes on the Upper Nile, expressly says: "that any mission to such savages is absolutely useless. They stand far below unreasoning animals; the latter at least show signs of affection towards those who are kind towards them, whereas these brutal natives are utterly incapable of any feeling of grat.i.tude."

Now, it clearly follows from these and other testimonies, that the mental differences between the lowest men and the animals are less than those between the lowest and the highest men; and if, together with this, we take into consideration the fact that in every single human child mental life develops slowly, gradually, and step by step, from the lowest condition of animal unconsciousness, need we still feel offended when told that the mind of the whole human race has in like manner gone through a process of slow, gradual, and historical development? Can we find it "degrading" to the human soul that, by a long and slow process of differentiation and perfecting, it has very gradually developed out of the soul of vertebrate animals? I freely acknowledge that this objection, which is at present raised by many against the pithecoid theory, is quite incomprehensible to me. On this point Bernhard Cotta, in his excellent "Geologie der Gegenwart," very justly remarks: "Our ancestors may be a great honour to us; but it is much better if we are an honour to them!"(31)

Our Theory of Development explains the origin of man and the course of his historical development in the only natural manner. We see in his gradually ascensive development out of the lower vertebrata, the greatest triumph of humanity over the whole of the rest of Nature. We are proud of having so immensely outstripped our lower animal ancestors, and derive from it the consoling a.s.surance that in future also, mankind, as a whole, will follow the glorious career of progressive development, and attain a still higher degree of mental perfection. When viewed in this light, the Theory of Descent as applied to man opens up the most encouraging prospects for the future, and frees us from all those anxious fears which have been the scarecrows of our opponents.

We can even now foresee with certainty that the complete victory of our Theory of Development will bear immensely rich fruits-fruits which have no equal in the whole history of the civilization of mankind. Its first and most direct result-the complete reform of _Biology_-will necessarily be followed by a still more important and fruitful reform of _Anthropology_. From this new theory of man there will be developed a new _philosophy_, not like most of the airy systems of metaphysical speculation hitherto prevalent, but one founded upon the solid ground of Comparative Zoology. A beginning of this has already been made by the great English philosopher Herbert Spencer.(45) Just as this new monistic philosophy first opens up to us a true understanding of the real universe, so its application to practical human life must open up a new road towards moral perfection. By its aid we shall at last begin to raise ourselves out of the state of social barbarism in which, notwithstanding the much vaunted civilization of our century, we are still plunged. For, unfortunately, it is only too true, as Alfred Wallace remarks with regard to this, at the end of his book of travels: "Compared with our wondrous progress in physical science and its practical applications, our system of government, of administering justice, of national education, and our whole social and moral organisation remains in a state of barbarism."

This social and moral barbarism we shall never overcome by the artificial and perverse training, the one-sided and defective teaching, the inner untruth and the external tinsel, of our present state of civilization. It is above all things necessary to make a complete and honest return to Nature and to natural relations. This return, however, will only become possible when man sees and understands his true "place in nature." He will then, as Fritz Ratzel has excellently remarked,(47) "no longer consider himself an _exception_ to natural laws, but begin to seek for what is lawful in his own actions and thoughts, and endeavour to lead a life _according_ to natural laws." He will come to arrange his life with his fellow-creatures-that is, the family and the state-not according to the laws of distant centuries, but according to the rational principles deduced from knowledge of nature. Politics, morals, and the principles of justice, which are still drawn from all possible sources, will have to be formed in accordance with natural laws only. An _existence worthy of man_, which has been talked of for thousands of years, will at length become a reality.

The highest function of the human mind is perfect knowledge, fully developed consciousness, and the moral activity arising from it. "Know thyself!" was the cry of the philosophers of antiquity to their fellow-men who were striving to enn.o.ble themselves. "Know thyself!" is the cry of the Theory of Development, not merely to the individual, but to all mankind. And whilst increased knowledge of self becomes, in the case of every individual man, a strong force urging to an increased attention to conduct, mankind as a whole will be led to a higher path of moral perfection by the knowledge of its true origin and its actual position in Nature. The simple religion of Nature, which grows from a true knowledge of Her, and of Her inexhaustible store of revelations, will in future enn.o.ble and perfect the development of mankind far beyond that degree which can possibly be attained under the influence of the multifarious religions of the churches of the various nations,-religions resting on a blind belief in the vague secrets and mythical revelations of a sacerdotal caste. Future centuries will celebrate our age, which was occupied with laying the foundations of the Doctrine of Descent, as the new era in which began a period of human development, rich in blessings,-a period which was characterized by the victory of free inquiry over the despotism of authority, and by the powerful enn.o.bling influence of the Monistic Philosophy.

FOOTNOTES:

[1] With the exception of a single specimen of the bones of a foot, preserved in the cabinet of Amherst College.-E. R. L.

[2] The primary stock of the Coniferae divided into two branches at an early period, into the Araucariae on the one hand, and the Taxaceae, or yew-trees, on the other. The majority of recent Coniferae are derived from the former. Out of the latter the third cla.s.s of the Gymnosperms-the Meningos, or Gnetaceae-were developed. This small but very interesting cla.s.s contains only three different genera-Gnetum, Welwitschia, and Ephedra; it is, however, of great importance, as it forms the transition group from the Coniferae to the Angiosperms, and more especially to the Dicotyledons.

[3] "Ueber ein Aequivalent der takonischen Schiefer Nordamerikas in Deutschland."

[4] The English word "Insects" might with advantage be used in the Linnaean sense for the whole group of Arthropods. In this case the Hexapod Insects might be spoken of as the Flies.-E. R. L.

[5] Weisbach: "Novara-Reise," Anthropholog. Theil.

[6] Musset im Naturbetrachten Immer Eins wie Alles achten.

Nichts ist drinnen, Nichts ist drauszen, Denn was innen, das ist auszen.

[7] Natur hat weder Kern noch Schale, Alles ist sie mit einem Male.