Dialectics, so-called objective dialectics, prevails throughout nature, and so-called subjective dialectics, dialectical thought, is only the reflection of the motion through opposites which asserts itself everywhere in nature, and which by the continual conflict of the opposites and their final passage into one another, or into higher forms, determines the life of nature. Attraction and repulsion. Polarity begins with magnetism, it is exhibited in one and the same body; in the case of electricity it distributes itself over two or more bodies which become oppositely charged. All chemical processes reduce themselves to processes of chemical attraction and repulsion. Finally, in organic life the formation of the cell nucleus is likewise to be regarded as a polarisation of the living protein material, and from the simple cell onwards the theory of evolution demonstrates how each advance up to the most complicated plant on the one side, and up to man on the other, is effected by the continual conflict between heredity and adaptation. In this connection it becomes evident how little applicable to such forms of evolution are categories like positive and negative. One can conceive of heredity as the positive, conservative side, adaptation as the negative side that continually destroys what has been inherited, but one can just as well take adaptation as the creative, active, positive activity, and heredity as the resisting, passive, negative activity. But just as in history progress makes its appearance as the negation of the existing state of things, so here also on purely practical grounds adaptation is better conceived as negative activity. In history, motion through opposites is most markedly exhibited in all critical epochs of the foremost peoples. At such moments a people has only the choice between the two horns of a dilemma: either-or! and indeed the question is always put in a way quite different from that in which the philistines, who dabble in politics in every age, would have liked it put. Even the liberal German philistine of 1848 found himself in 1849 suddenly, unexpectedly, and against his will confronted by the question: a return to the old reaction in an intensified form, or continuance of the revolution up to the republic, perhaps even the one and indivisible republic with a socialist background. He did not spend long in reflection and helped to create the Manteuffel reaction as the flower of German liberalism. Similarly, in 1851, the French bourgeois when faced with the dilemma which he certainly did not expect: a caricature of the empire, pretorian rule, and the exploitation of France by a gang of scoundrels, or a social-democratic republic and he bowed down before the going of scoundrels so as to be able, under their protection, to go on exploiting the workers. Hard and fast lines are incompatible with the theory of evolution. Even the border-line between vertebrates and invertebrates is now no longer rigid, just as little is that between fishes and amphibians, while that between birds and reptiles dwindles more and more every day. Between Compsognathus and Archaopteryx only a few intermediate links are wanting, and birds beaks with teeth crop up in both hemispheres. Either-or becomes more and more inadequate. Among lower animals the concept of the individual cannot be established at all sharply. Not only as to whether a particular animal is an individual or a colony, but also where in development one individual ceases and the other begins (nurses). For a stage in the outlook on nature where all differences become merged in intermediate steps, and all opposites pass into one another through intermediate links, the old metaphysical method of thought no longer suffices. Dialectics, which likewise knows no hard and fast lines, no unconditional, universally valid either-or and which bridges the fixed metaphysical differences, and besides either-or recognises also in the right place both this-and that and reconciles the opposites, is the sole method of thought appropriate in the highest degree to this stage. Of course, for everyday use, for the small change of science, the metaphysical categories retain their validity. The transformation of quantity into quality= mechanical world outlook, quantitative change alters quality. The gentlemen never suspected that! The character of mutual opposites belonging to the thought determinations of reason: polarisation. Just as electricity, magnetism, etc., become polarised and move in opposites, so do thoughts. Just as in the former it is not possible to maintain any one-sidedness, and no natural scientist would think of doing so, so also in the latter. The true nature of the determinations of essence is expressed by Hegel himself (Enzyklop die, I, paragraph III, addendum): In essence everything is relative (e.g., positive and negative, which have meaning only in their relation, not each for itself). Part and whole, for instance, are already categories which become inadequate in organic nature. The ejection of seeds the embryo and the new-born animal are not to be conceived as a part that is separated from the whole ; that would give a distorted treatment. It becomes a part only in a dead body. (Enzyklop die, I, p. 268.) Simple and compound. Categories which even in organic nature likewise lose their meaning and become inapplicable. An animal is expressed neither by its mechanical composition from bones, blood, gristle, muscles, tissues, etc., .nor by its chemical composition from the elements. Hegel (Enzyklop die, I, p. 256). The organism is neither simple nor compound, however complex it may be. Abstract identity (a=a; and negatively, a cannot be simultaneously equal and unequal to a) is likewise inapplicable in organic nature. The plant, the animal, every cell is at every moment of its life identical with itself and yet becoming distinct from itself, by absorption and excretion of substances, by respiration, by cell formation and death of cells, by the process of circulation taking place, in short, by a sum of incessant molecular changes which make up life and the sum-total of whose results is evident to our eyes in the phases of life embryonic life, youth, sexual maturity, process of reproduction, old age, death. The further physiology develops, the more important for it become these incessant, infinitely small changes, and hence the more important for it also the consideration of difference within identity, and the old abstract standpoint of formal identity, that an organic being is to be treated as something simply identical with itself, as something constant, becomes out of date. [In the margin of the manuscript occurs the remark: Apart, moreover, from the evolution of species. ] Nevertheless, the mode of thought based thereon, together with its categories, persists. But even in inorganic nature identity as such is in reality non-existent. Every body is continually exposed to mechanical, physical, and chemical influences, which are always changing it and modifying its identity. Abstract identity, with its opposition to difference, is in place only in mathematics an abstract science which is concerned with creations of thought, even though they are reflections of reality and even there it is continually being sublated. Hegel, Enzyklop die, I, p. 235. The fact that identity contains difference within itself is expressed in every sentence, where the predicate is necessarily different from the subject; the lily is a plant, the rose, is red, where, either in the subject or in the predicate, there is something that is not covered by the predicate or the subject. Hegel, p. 231. That from the outset identity with itself requires difference from everything else as its complement, is self-evident. Continual change, i.e., sublation of abstract identity with itself, is also found in so-called inorganic nature. Geology is its history. On the surface, mechanical changes (denudation, frost), chemical changes (weathering); internally, mechanical changes (pressure), heat (volcanic), chemical (water, acids, binding substances); on a large scale upheavals, earthquakes, etc. The slate of today is fundamentally different from the ooze from which it is formed, the chalk from the loose microscopic shells that compose it, even more so limestone, which indeed according to some is of purely organic origin, and sandstone from the loose sea sand, which again is derived from disintegrated granite, etc., not to speak of coal. The law of identity in the old metaphysical sense is the fundamental law of the old outlook: a=a. Each thing is equal to itself. Everything was permanent, the solar system, stars, organisms. This law has been refuted by natural science bit by bit in each separate case, but theoretically it still prevails and is still put forward by the supporters of the old in opposition to the new: a thing cannot simultaneously be itself and something else. And yet the fact that true, concrete identity includes difference, change, has recently been shown in detail by natural science (see above). Abstract identity, like all metaphysical categories, suffices for everyday use, where small dimensions or brief periods of time are in question; the limits within which it is usable differ in almost every case and are determined by the nature of the object; for a planetary system, where in ordinary astronomical calculation the ellipse can be taken as the basic form for practical purposes without error, they are much wider than for an insect that completes its metamorphosis in a few weeks. (Give other examples, e.g., alteration of species, which is reckoned in periods of thousands of years.) For natural science in its comprehensive role, however, even in each single branch, abstract identity is totally inadequate, and although on the whole it has now been abolished in practice, theoretically it still dominates people s minds, and most natural scientists imagine that identity and difference are irreconcilable opposites, instead of one-sided poles which represent the truth only in their reciprocal action, in the inclusion of difference within identity. Identity and difference necessity and chance cause and effect the two main opposites [In the manuscript: die beiden Hauptgegensatze (the two main opposites). Engels has in mind: (1) The antithesis of identity and difference, and (2) the antithesis of cause and effect. The words necessity and chance were written between the lines afterwards.] which, treated separately, become transformed into one another. And then first principles must help. Positive and negative. Can also be given the reverse names: in electricity, etc.; North and South ditto. If one reverses this and alters the rest of the terminology accordingly, everything remains correct. We can call West East and East West. The sun rises in the West, and planets revolve from East to West, etc., the names alone are changed. Indeed, in physics we call the real South pole of the magnet, which is attracted by the North pole, of the earth s magnetism, the North pole, and it does not matter. That positive and negative are equivalent, irrespective of which side is positive and which negative, (holds good) not only in analytical geometry, but still more in physics (see Clausius, p. 87 et seq.). Polarity. A magnet, on being cut through, polarises the neutral middle portion, but in such a way that the old poles remain. On the other hand a worm, on being cut into two, retains the receptive mouth at the positive pole and forms a new negative pole at the other end with excretory anus; but the old negative pole (the anus) now becomes positive, becoming a mouth, and a new anus or negative pole is formed at the cut end. Voila transformation of positive into negative. Polarisation. For J. Grimm it was still a firmly established law that a German dialect must be either High German or Low German. In this he totally lost sight of the Frankish dialect. Because the written Frankish of the later Carlovingian period was High German (since the High German shifting of consonants had taken possession of the Frankish South-East), he imagined that Frankish passed in one place into old High German, in another place into French. It then remained absolutely impossible to explain the source of the Netherland dialect in the ancient Salic regions. Frankish was only rediscovered after Grimm s death: Salic in its rejuvenation as the Netherland dialect, Ripuaric in the Middle and Lower Rhine dialects, which in part have been shifted to various stages of High German, and in part have remained Low German, so that Frankish is a dialect that is both High German and Low German. Another opposition in which metaphysics is entangled is that of chance and necessity. What can be more sharply contradictory than these two thought determinations? How is it possible that both are identical, that the accidental is necessary, and the necessary is also accidental? Common sense, and with it the majority of natural scientists, treats necessity and chance as determinations that exclude each other once for all. A thing, a circumstance, a process is either accidental or necessary, but not both. Hence both exist side by side in nature; nature contains all sorts of objects and processes, of which some are accidental, the others necessary, and it is only a matter of not confusing the two sorts with each other. Thus, for instance, one assumes the decisive specific characters to be necessary, other differences between individuals of the same species being termed accidental, and this holds good of crystals as it does for plants and animals. Then again the lower group becomes accidental in relation to the higher, so that it is declared to be a matter of chance how many different species are included in the genus felis or equus, or how many genera and orders there are in a class, and how many individuals of each of these species exist, or how many different species of animals occur in a given region, or what in general the fauna and flora are like. And then it is declared that the necessary is the sole thing of scientific interest and that the accidental is a matter of indifference to science. That is to say: what can be brought under laws, hence what one knows, is interesting; what cannot be brought under laws, and therefore what one does not know, is a matter of indifference and can be ignored. Thereby all science comes to an end, for it has to investigate precisely that which we do not know. That is to say: what can be brought under general laws is regarded as necessary, and what cannot be so brought as accidental. Anyone can see that this is the same sort of science as that which proclaims natural what it can explain, and ascribes what it cannot explain to supernatural causes; whether I term the cause of the inexplicable chance, or whether I term it God, is a matter of complete indifference as far as the thing itself is concerned. Both are only equivalents for: I do not know, and therefore do not belong to science. The latter ceases where the requisite connection is wanting. In opposition to this view there is determinism, which passed from French materialism into natural science, and which tries to dispose of chance by denying it altogether. According to this conception only simple, direct necessity prevails in nature. That a particular pea-pod contains five peas and not four or six, that a particular dog s tail is five inches long and not a whit longer or shorter, that this year a particular clover flower was fertilised by a bee and another not, and indeed by precisely one particular bee and at a particular time, that a particular windblown dandelion seed has sprouted and another not, that last night I was bitten by a flea at four o clock in the morning, and not at three or five o clock, and on the right shoulder and not on the left calf these are all facts which have been produced by an irrevocable concatenation of cause and effect, by an unshatterable necessity of such a nature indeed that the gaseous sphere, from which the solar system was derived, was already so constituted that these events had to happen thus and not otherwise. With this kind of necessity we likewise do not get away from the theological conception of nature. Whether with Augustine and Calvin we call it the eternal decree of God, or Kismet as the Turks do, or whether we call it necessity, is all pretty much the same. for science. There is no question of tracing the chain of causation in any of these cases; so we are just as wise in one as in another, the so-called necessity remains an empty phrase, and with it chance also remains what it was before. As long as we are not able to show on what the number of peas in the pod depends, it remains just a matter of chance, and the assertion that the case was foreseen already in the primordial constitution of the solar system does not get us a step further. Still more. A science which was to set about the task of following back the casus of this individual pea-pod in its causal concatenation would be no longer science but pure trifling; for this same peapod alone has in addition innumerable other individual, accidentally appearing qualities: shade of colour, thickness and hardness of the pod, size of the peas, not to speak of the individual peculiarities revealed by the microscope. The one pea-pod, therefore, would already provide more causal connections for following up than all the botanists in the world could solve. Hence chance is not here explained by necessity, but rather necessity is degraded to the production of what is merely accidental. If the fact that a particular pea-pod contains six peas, and not five or seven, is of the same order as the law of motion of the solar system, or the law of the transformation of energy, then as a matter of fact chance is not elevated into necessity, but rather necessity degraded into chance. Furthermore, however much the diversity of the organic and inorganic species and individuals existing side by side in a given area may be asserted to be based on irrefragable necessity, for the separate species and individuals it remains what it was before, a matter of chance. For the individual animal it is a matter of chance, where it happens to be born, what environment it finds for living, what enemies and how many of them threaten it. For the mother plant it is a matter of chance whither the wind scatters its seeds, and, for the daughter plant, where the seed finds soil for germination; and to assure us that here also everything rests on irrefragable necessity is a poor consolation. The jumbling together of natural objects in a given region, still more in the whole world, for all the primordial determination from eternity, remains what it was before a matter of chance. In contrast to both conceptions, Hegel came forward with the hitherto quite unheard-of propositions that the accidental has a cause because it is accidental, and just as much also has no cause because it is accidental; that the accidental is necessary, that necessity determines itself as chance, and, on the other hand, this chance is rather absolute necessity. (Logik, II, Book III, 2: Reality.) Natural science has simply ignored these propositions as paradoxical trifling, as self-contradictory nonsense, and, as regards theory, has persisted on the one hand in the barrenness of thought of Wolffian metaphysics, according to which a thing is either accidental or necessary, but not both at once; or, on the other hand, in the hardly less thoughtless mechanical determinism which in words denies chance in general only to recognise it in practice in each particular case. While natural science continued to think in this way, what did it do in the person of Darwin? Darwin in his epoch-making work, set out from the widest existing basis of chance. Precisely the infinite, accidental differences between individuals within a single species, differences which become accentuated until they break through the character of the species, and whose immediate causes even can be demonstrated only in extremely few cases, compelled him to question the previous basis of all regularity in biology, viz., the concept of species in its previous metaphysical rigidity and unchangeability. Without the concept of species, however, all science was nothing. All its branches needed the concept of species as basis: human anatomy and comparative anatomy embryology, zoology, palaeontology, botany, etc., what were they without the concept of species? All their results were not only put in question but directly set aside. Chance overthrows necessity, as conceived hitherto. [Note in the margin of the manuscript: The material on chance occurrences accumulated in the meantime has suppressed and shattered the old idea of necessity. ] The previous idea of necessity breaks down. To retain it means dictatorially to impose on nature as a law a human arbitrary determination that is in contradiction to itself and to reality, it means to deny thereby all inner necessity in living nature, it means generally to proclaim the chaotic kingdom of chance to be the sole law of living nature. Gilt nichts mehr der Tausves Jontof,  cried out quite logically the biologists of all schools. Darwin. Negation of the negation. Phanomenologie, Preface, p. 4. Bud, flower, fruit, etc. Unity of nature and mind. To the Greeks it was self-evident that nature could not be unreasonable, but even today the stupidest empiricists prove by their reasoning (however wrong it may be) that they are convinced from the outset that nature cannot be unreasonable or reason contrary to nature. The evolution of a concept, or of a conceptual relation (positive and negative, cause and effect, substance and accidency) in the history of thought, is related to its development in the mind of the individual dialectician, just as the evolution of an organism in palaeontology is related to its development in embryology (or rather in history and in the single embryo). That this is so was first discovered for concepts by Hegel. In historical development, chance plays its part, which in dialectical thinking, as in the development of the embryo, is summed up in necessity. Abstract and concrete. The general law of the change of form of motion is much more concrete than any single concrete example of it. Understanding and reason. This Hegelian distinction, according to which only dialectical thinking is reasonable, has a definite meaning. We have in common with animals all activity of the understanding: induction, deduction, and hence also abstraction (Dido s, generic concepts: quadrupeds and bipeds), analysis of unknown objects (even the cracking of a nut is a beginning of analysis), synthesis (in animal tricks), and, as the union of both, experiment (in the case of new obstacles and unfamiliar situations). In their nature all these modes of procedure hence all means of scientific investigation that ordinary logic recognises are absolutely the same in men and higher animals. They differ only in degree (of development of the method in each case) The basic features of the method are the same and lead to the same results in man and animals, so long as both operate or make shift, merely with these elementary methods. On the other hand, dialectical thought precisely because it presupposes investigations of the nature, of concepts themselves is only possible for man, and for him only at a comparatively high stage of development (Buddhists and Greeks), and it attains its full development much later still through modern philosophy and yet we have the colossal results already among the Greeks which by far anticipate investigation! Dialectical logic, in contrast to the old, merely formal logic, is not, like the latter, content with enumerating the forms of motion of thought, i.e., the various forms of judgment and conclusion, and placing them side by side without any connection. On the contrary, it derives these forms out of one another, it makes one subordinate to another instead of putting them on an equal level, it develops the higher forms out of the lower. Faithful to his division. of the whole of logic, Hegel groups judgments as: 1. Judgment of inherence, the simplest form of judgment, in which a general property is affirmatively or negatively predicated of a single thing (positive judgment: the rose is red; negative judgment: the rose is not blue; infinite judgment: the rose is not a camel); 2. Judgment of subsumption, in which a relation determination is predicated of the subject (singular judgment: this man is mortal; particular judgment: some, many men are mortal; universal judgment: all men are mortal, or man is mortal); 3. Judgment of necessity, in which its substantial determination is predicated of the subject (categorical judgment: the rose is a plant; hypothetical judgment: when the sun rises it is day-time; disjunctive judgment: Lepidosiren is either a fish or an amphibian); 4. Judgment of the notion, in which is predicated of the subject how far it corresponds to its general nature or, as Hegel says, to the notion of it (assertoric judgment: this house is bad; problematic judgment: if a house is constituted in such and such a way, it is good apodeictic judgment: the house that is constituted in such and such a way is good. 1. Individual Judgment. 2 and 3. Special. 4. General. However dry this sounds here, and however arbitrary at first sight this classification of judgments may here and there appear, yet the inner truth and necessity of this grouping will become clear to anyone who studies the brilliant exposition in Hegel s Larger Logic. (Works, V, pp. 63-115.)  To show how much this grouping is based not only on the laws of thought but also on the laws of nature, we should like to put forward here a very wellknown example outside this connection. That friction produces heat was already known practically to prehistoric man, who discovered the making of fire by friction perhaps more than 100,000 years ago, and who still earlier warmed cold parts of the body by rubbing. But from that to the discovery that friction is in general a source of heat, who knows how many thousands of years elapsed? Enough that the time came when the human brain was sufficiently developed to be able to formulate the judgment: friction is a source of heat, a judgment of inherence, and indeed a positive one. Still further thousands of years passed until, in 1842, Mayer, Joule, and Colding investigated this special process in its relation to other processes of a similar kind that had been discovered in the meantime, i.e., as regards its immediate general conditions, and formulated the judgment: all mechanical motion is capable of being converted into heat by means of friction. So much time and an enormous amount of empirical knowledge were required before we could make the advance in knowledge of the object from the above positive judgment of inherence to this universal judgment of subsumption. But from now on things went quickly. Only three years later, Mayer was able, at least in substance, to raise the judgment of subsumption to the level at which it now stands: any form of motion, under conditions fixed for each case, is both able and compelled to undergo transformation, indirectly, into any other form of motion a judgment of the notion, and moreover an apodeictic one, the highest form of judgment altogether. What, therefore, in Hegel appears as a development of the thought form of judgment as such, confronts us here as, the development of our empirically based theoretical knowledge of the nature of motion in general. This shows, however, that laws of thought and laws of nature are necessarily in agreement with one another, if only they are correctly known. We can regard the first judgment as that of individuality; the isolated fact that friction produces heat is registered. The second judgment is that of particularity: a special form of motion, mechanical motion, exhibits the property, under special conditions (through friction), of passing into another special form of motion, viz., heat. The third judgment is that of universality: any form of motion proves able and compelled to undergo transformation into any other form of motion. In this form the law attains its final expression. By new discoveries we can give new illustrations of it, we can give it a new and richer content. But we cannot add anything to the law itself as here formulated. In its universality, equally universal in form and content, it is not susceptible of further extension: it is an absolute law of nature. Unfortunately we are in a difficulty about the form of motion of protein, alias life, so long as we are not able to make protein. Above, however, it has also been proved that to make judgments involves not merely Kant s power of judgment, but a [This unfinished note closes the fourth page of the double sheet of which the second and third pages and the beginning of the fourth page constitute the preceding large fragment on the classification of judgments. Engels apparently meant to finish the note by counterposing his thesis on the empirical basis of all knowledge to the Kantian apriorism.] Individuality, particularity, universality these are the three determinations in which the whole Doctrine of the Notion  moves. Under these heads, progression from the individual to the particular and from the particular to the universal takes place not in one but in many modalities, and this is often enough exemplified by Hegel as the progression: individual, species, genus. And now the Haeckels come forward with their induction and trumpet it as a great fact against Hegel that progression must be from the individual to the particular and then to the universal (!), from the individual to the species and then to the genus and then permit deductive conclusions which are supposed to lead further. These people have got into such a dead lock over the opposition between induction and deduction that they reduce all logical forms of conclusion to these two, and in so doing do not notice that they (1) unconsciously employ quite different forms of conclusion under those names, (2) deprive themselves of the whole wealth of forms of conclusion in so far as it cannot be forced under these two, and (3) thereby convert both forms, induction and deduction, into sheer nonsense. Induction and deduction. Haeckel, p. 75 et seq., where Goethe draws the inductive conclusion that man, who does not normally have a premaxillary bone, must have one, hence by incorrect induction arrives at something correct! Haeckel s nonsense: induction against deduction. As if it were not the case that deduction=conclusion, and therefore induction is also a deduction. This comes from polarisation. Haeckel s Schopfungsgeschichte, pp. 76-77. The conclusion polarised into induction and deduction! By induction it was discovered 100 years ago that crayfish and spiders were insects and all lower animals were worms. By induction it has now been found that this is nonsense and there exist x classes. Wherein then lies the advantage of the so-called inductive conclusion, which can be just as false as the so-called deductive conclusion, the basis of which is nevertheless classification? Induction can never prove that there will never be a mammal without lacteal glands. Formerly nipples were the mark of a mammal. But the platypus has none. The whole swindle of induction (is derived) from the Englishmen; Whewell, inductive sciences, comprising the purely mathematical [sciences], and so the antithesis to deduction invented. Logic, old or new, knows nothing of this. All forms of conclusion that start from the individual are experimental and based on experience, indeed the inductive conclusion even starts from U I P  (universal). It is also characteristic of the thinking capacity of our natural scientists that Haeckel fanatically champions induction at the very moment when the results of induction the classifications are everywhere put in question (Limulus a spider, Ascidia a vertebrate or chordate, the Dipnoi, however, being fishes, in opposition to all original definitions of amphibia) and daily new facts are being discovered which overthrow the entire previous classification by induction. What a beautiful confirmation of Hegel s thesis that the inductive conclusion is essentially a problematic one! Indeed, owing to the theory of evolution, even the whole classification of organisms has been taken away from induction and brought back to deduction, to descent one species being literally deduced from another by descent and it is impossible to prove the theory of evolution by induction alone, since it is quite anti-inductive. The concepts with which induction operates: species, genus, class, have been rendered fluid by the theory of evolution and so have become relative: but one cannot use relative concepts for induction. To the Pan-Inductionists. [In the manuscript: Den Allinduktionisten, i.e., to those who regard induction as the only correct method.] With all the induction in the world we would never have got to the point of becoming clear about the process of induction. Only the analysis of this process could accomplish this. Induction and deduction belong together as necessarily as synthesis and analysis. [Note in the margin: Chemistry, in which analysis is the predominant form of investigation, is nothing without its opposite synthesis.] Instead of one-sidedly lauding one to the skies at the expense of the other, we should seek to apply each of them in its place, and that can only be done by bearing in mind that they belong together, that they supplement each other. According to the inductionists, induction is an infallible method. It is so little so that its apparently surest results are every day overthrown by new discoveries. Light corpuscles and caloric were results of induction. Where are they now? Induction taught us that all vertebrates have a central nervous system differentiated into brain and spinal cord, and that the spinal cord is enclosed in cartilaginous or bony vertebrae whence indeed the name is derived. Then Amphioxus was revealed as a vertebrate with an undifferentiated central nervous strand and without vertebrae. Induction established that fishes are those vertebrates which throughout life breathe exclusively by means of gills. Then animals come to light whose fish character is almost universally recognised, but which, besides gills, have also well-developed lungs, and it turns out that every fish carries a potential lung in the swim bladder. Only by audacious application of the theory of evolution did Haeckel rescue the inductionists, who were feeling quite comfortable in these contradictions. If induction were really so infallible, whence come the rapid successive revolutions in classification of the organic world? They are the most characteristic product of induction, and yet they annihilate one another. Induction and analysis. A striking example of how little induction can claim to be the sole or even the predominant form of scientific discovery occurs in thermodynamics: the steam-engine provided the most striking proof that one can impart heat and obtain mechanical motion. 100,000 steam-engines did not prove this more than one, but only more and more forced the physicists into the necessity of explaining it. Sadi Carnot was the first seriously to set about the task. But not by induction. He studied the steam engine, analysed it, and found that in it the process which mattered does not appear in pure form but is concealed by all sorts of subsidiary processes. He did away with these subsidiary circumstances that have no bearing on the essential process, and an ideal steam-engine (or gas engine), which it is true is as little capable of being realised as, for instance, a geometrical line or surface but in Its way performs the same service as these mathematical abstractions: it presents the process in a pure, independent, and unadulterated form. And he came right up against the mechanical equivalent of heat (see the significance of his function C), which he only failed to discover and see because he believed in caloric. Here also proof of the damage done by false theories. The empiricism of observation alone can never adequately prove necessity. Post hoc but not propter hoc. (Enzyklop die, I, S, 84.) This is so very correct that it does not follow from the continual rising of the sun in the morning that it will rise again tomorrow, and in fact we know now that a time will come when one morning the sun will not rise. But the proof of necessity lies in human activity, in experiment, in work: if I am able to make the post hoc, it becomes identical with the propter hoc. Causality. The first thing that strikes us in considering matter in motion is the inter-connection of the individual motions of separate bodies, their being determined by one another. But not only do we find that a particular motion is followed by another, we find also that we can evoke a particular motion by setting up, the conditions in which it takes place in nature, that we can even produce motions which do not occur at all in nature (industry), at least not in this way, and that we can give these motions a predetermined direction and extent. In this way, by the activity of human beings the idea of causality becomes established, the idea that one motion is the cause of another. True, the regular sequence of certain natural phenomena can by itself give rise to the idea of causality: the heat and light that come with the sun; but this affords no proof, and to that extent Hume s scepticism was correct in saying that a regular post hoc can never establish a propter hoc. But the activity of human beings forms the test of and make them by prove that heat comes from the sun. If we bring together in a rifle the priming, the explosive charge, and the bullet and then fire it, we count upon the effect known in advance from previous experience, because we can follow in all its details the whole process of ignition, combustion, explosion by the sudden conversion into gas and pressure of the gas on the bullet. And here the sceptic cannot even say that because of previous experience it does not follow that it will be the same next time. For, as a matter of fact, it does sometimes happen that it is not the same, that the priming or the gunpowder fails to work, that the barrel bursts, etc. But surely this which proves causality instead of refuting it, because we can find out the cause of each such deviation from the rule by appropriate investigation: chemical decomposition of the priming, dampness, etc., of the gunpowder, defect in the barrel, etc., etc., so that here the test of causality is so to say a double one. Natural science, like philosophy, has hitherto entirely neglected the in influence of activity on their thought; both know only nature on the one hand and thought on the other. But it is precisely the alteration of nature by men, not solely nature as such, which is most essential and immediate basis of human thought, and it is in the measure that man has learned to change nature that his intelligence has increased. The naturalistic conception of history, as found, for instance to a greater or lesser extent in Draper and other scientists, as if nature exclusively reacts on man, and natural conditions everywhere exclusively determined his historical development, is therefore one-sided and forgets that man also reacts on nature, changing it and creating new conditions of existence for himself. There is devilishly little left of nature as it was in Germany at the time when the Germanic peoples immigrated into it. The earth s surface, climate, vegetation, fauna, and the human beings themselves have infinitely changed, and all this owing to human activity, while the changes of nature in Germany which have occurred in this period of time without human interference are incalculably small. Reciprocal action is the first thing that we encounter when we consider matter in motion as A whole from the standpoint of modern natural science. We see a series of forms of motion, mechanical motion, heat, light, electricity, magnetism, chemical union and decomposition, transitions of states of aggregation, organic life, all of which, if at present we still make an exception of organic life, pass into one another, mutually determine one another, are in one place cause and in another effect, the sum-total of the motion in all its changing forms remaining the same (Spinoza: substance is causa sui strikingly expresses the reciprocal action). Mechanical motion becomes transformed into heat, electricity, magnetism, light, etc., and vice versa. Thus natural science confirms what Hegel has said (where?), that reciprocal action is the true causa finalis of things. We cannot go back further than to knowledge of this reciprocal action, for the very reason that there is nothing behind to know. If we know the forms of motion of matter (for which it is true there is still very much lacking, in view of the short time that natural science has existed), then we know matter itself, and therewith our knowledge is complete. (Grove s whole misunderstanding about causality rests on the fact that he does not succeed in arriving at the category of reciprocal action; he has the thing, but not the abstract thought, and hence the confusion pp. 10-14.) Only from this universal reciprocal action do we arrive at the real causal relation. In order to understand the separate phenomena, we have to tear them out of the general inter-connection and consider them in isolation, and then the changing motions appear, one as cause and the other as effect. For one who denies causality every natural law is a hypothesis, among others also the chemical analysis of heavenly bodies by means of the prismatic spectrum. What shallowness of thought to remain at such a viewpoint! N geli first of all says that we cannot know real qualitative differences, and immediately afterwards says that such absolute differences do not occur in nature! (p. 12.) Firstly, every quality has infinitely many quantitative gradations, e.g., shades of colour, hardness and softness, length of life, etc., and these, although qualitatively distinct, are measurable and knowable. Secondly, qualities do not exist but only things with qualities and indeed with infinitely many qualities. Two different things always have certain qualities (properties of corporeality at least) in common, others differing in degree, while still others may be entirely absent in one of them. If we consider two such extremely different things e.g., a meteorite and a man in separation, we get very little out of it, at most that heaviness and other general properties of bodies are common to both. But an infinite series of other natural objects and natural processes can be put between the two things, permitting us to complete the series from meteorite to man and to allocate to each its place in the inter-connection of nature and thus to know them. N geli himself admits this.. Thirdly, our various senses might give us impressions differing absolutely as regards quality. In that case, properties which we experience by means of sight, hearing, smell, taste, and touch would be absolutely different. But even here the differences disappear with the progress of investigation. Smell and taste have long ago been recognised as allied senses belonging together, which perceive conjoint if not identical properties. Sight and hearing both perceive wave oscillations. Touch and sight supplement each other to such an extent that from. the appearance of an object we can often enough predict its tactile properties. And, finally, it is always the same I that receives and elaborates all these different sense impressions, that therefore comprehends them into a unity, and likewise these various. impressions are provided by the same thing, appearing as its common properties, and therefore helping us to know it. To explain these different properties accessible only to different senses, to bring them into connection with one another, is precisely the task of science, which so far has not complained because we have not a general sense in place of the five special senses, or because we are not able to see or hear tastes and smells. Wherever we look, nowhere in nature are there to be found such qualitatively* or absolutely distinct fields, [p.. 12) which are alleged to be incomprehensible. The whole confusion springs from the confusion about quality and quantity. In accordance with the prevailing mechanical view, N geli regards all qualitative differences as explained only in so far as they can be reduced to quantitative differences (on which what is necessary is said elsewhere), or because quality and quantity are for him absolutely distinct categories. Metaphysics. This is quite correct in so far as only finite objects enter the sphere of our knowledge. But the proposition needs to be supplemented by this: fundamentally we can know only the infinite. In fact all real, exhaustive knowledge consists solely in raising the individual thing in thought from individuality into particularity and from this into universality, in seeking and establishing the infinite in the finite, the eternal in the transitory. The form of universality, however, is the form of self-completeness, hence of infinity; it is the comprehension of the many finites in the infinite. We know that chlorine and hydrogen, within certain limits of temperature and pressure and under the influence of light, combine with an explosion to form hydrochloric acid gas, and as soon as we know this, we know also, that this takes place everywhere and at all times where the above conditions are present, and it can be a matter of indifference, whether this occurs once or is repeated a million times, or on how many heavenly bodies. The form of universality in nature is law, and no one talks more of the eternal character of the laws of nature than the natural scientists. Hence when N geli says that the finite is made impossible to understand by not desiring to investigate merely this finite, but instead adding something eternal to it, then he denies either the possibility of knowing the laws of nature or their eternal character. All true knowledge of nature is knowledge of the eternal, the infinite, and hence essentially absolute. But this absolute knowledge has an important drawback. Just as the infinity of knowable matter is composed of the purely finite things, so the infinity of the thought which knows the absolute is composed of an infinite number of finite human minds, working side by side and successively at this infinite knowledge, committing practical and theoretical blunders, setting out from erroneous, one-sided, and false premises, pursuing false, tortuous, and uncertain paths, and often not even finding what is right when they run their noses against it (Priestley). The cognition of the infinite is therefore beset with double difficulty and from its very nature can only take place in an infinite asymptotic progress. And that fully suffices us in order to be able to say: the infinite is just as much knowable as unknowable, and that is all that we need. Curiously enough, N geli says the same thing: The finite that comes into the sphere, etc., constitutes in sum precisely the infinite, for it is just from this that N geli has derived his idea of the infinite! Without this finite, etc., he would have indeed no idea of the infinite! (Bad infinity, as such, to be dealt with elsewhere.) Before this investigation of infinity comes the following: It is the old story. First of all one makes sensuous things into abstractions and then one wants to know them through, the senses, to see time and smell space. The empiricist becomes so steeped in the habit of empirical experience, that he believes that he is still in the field of sensuous experience when he is operating with abstractions. We know what an hour is, or a metre, but not what time and space are! As if time was anything other than just hours, and space anything but just cubic metres! The two forms of existence of matter are naturally nothing without matter, empty concepts, abstractions which exist only in our minds. But, of course, we are supposed not to know what matter and motion are! Of course not, for matter as such and motion as such have not yet been seen or otherwise experienced by anyone, only the various existing material things and forms of motions. Matter is nothing but the totality of material things from which this concept is abstracted and motion as such nothing but the totality of all sensuously perceptible forms of motion; words like matter and motion are nothing but abbreviations in which we comprehend many different sensuous perceptible things according to their common properties. Hence matter and motion can be known in no other way than by investigation of the separate material things and forms of motion, and by knowing these, we also pro tanto know matter and motion as such. Consequently, in saying that we do not know what time, space, matter, motion, cause and effect are, N geli merely says that first of all we make abstractions of the real world through our minds, and then can not know these self-made abstractions because they are creations of thought and not sensuous objects, while all knowing is sensuous measurement! This is just like the difficulty mentioned by Hegel; we can eat cherries and plums, but not fruit, because no one has so far eaten fruit as such. When N geli asserts that there are probably a whole number of forms of motion in nature which we cannot perceive by our senses, that is a poor apology, equivalent to the suspension at least for our knowledge of the law of the uncreatability of motion. For they could certainly be transformed into motion perceptible to us! That would be an easy explanation of, for instance, contact electricity. Ad vocem N geli. Impossibility of conceiving the infinite. When we say that matter and motion are not created and are indestructible, we are saying, that the world exists as infinite progress, i.e., in the form of bad infinity, and thereby we have understood all of this process that is to be understood. At the most the question still arises whether this process is an eternal repetition in great cycles or whether the cycles have descending and ascending branches. Bad infinity. True infinity was already correctly put by Hegel in filled space and time, in the process of nature and in history. The whole of nature also is now merged in history, and history is only differentiated from natural history as the evolutionary process of self-conscious organisms. This infinite complexity of nature and history has within it the infinity of space and time bad infinity only as a sublated factor, essential but not predominant. The extreme limit of our natural science until now has been our universe, and we do not need the infinitely numerous universes outside it to have knowledge of nature. Indeed, only a single sun among millions, with its solar system, forms the essential basis of our astronomical researches. For terrestrial mechanics, physics, and chemistry we are more or less restricted to our little earth, and for organic science entirely so. Yet this does not do any essential injury to the practically infinite diversity of phenomena and natural knowledge, any more than history is harmed by the similar, even greater limitation to a comparatively short period and small portion of the earth. 1. According to Hegel, infinite progress is a barren waste because it appears only as eternal repetition of the same thing: 1+1+1, etc. 2. In reality, however, it is no repetition, but a development, an advance or regression, and thereby it becomes a necessary form of motion. This apart from the fact that it is not infinite: the end of the earth s lifetime can already be foreseen. But then, the earth is not the whole universe. In Hegel s system, any development was excluded from the temporal history of nature, otherwise nature would not be the being-beyond-self of spirit. But in human history infinite progress is recognised by Hegel as the, sole true form of existence of spirit, except that fantastically this development is assumed to have an end in the production of the Hegelian philosophy. 3. There is also infinite knowing (Quantity, p. 259. Astronomy): questa infinita che le cose non hanno in progresso, la hanno in giro. [This infinite, which things do not have in progress, they have In circling.] Thus the law of the change of form of motion is an infinite one, including itself in itself. Such infinities, however, are in their turn smitten with finiteness, and only occur piecemeal. So also 1/r2.  The eternal laws of nature also become transformed more and more into historical ones. That water is fluid from 0 -100 C. is an eternal law of nature, but for it to be valid, there must be (1) water, (2) the given temperature, (3) normal pressure. On the moon there is no water, in the sun only its elements, and the law does not exist for these two heavenly bodies. The laws of meteorology are also eternal, but only for the earth or for a body of the size, density, axial inclination, and temperature of the earth, and on condition that it has an atmosphere of the same mixture of oxygen and nitrogen and with the same amounts of water vapour being evaporated and precipitated. The moon has no atmosphere, the sun one of glowing metallic vapours; the former has no meteorology, that of the latter is quite different from ours. Our whole official physics, chemistry, and biology are exclusively geocentric, calculated only for the earth. We are still quite ignorant of the conditions of electric and magnetic tensions on the sun, fixed stars, and nebulae, even on the planets of a different density from ours. On the sun, owing to high temperature, the laws of chemical combination of the elements are suspended or only momentarily operative at the limits of the solar atmosphere, the compounds becoming dissociated again on approaching the sun. The chemistry of the sun is just in process of arising, and is necessarily quite different from that of the earth, not overthrowing the latter but standing outside it. In the nebulae perhaps there do not exist even those of the 65 elements which are possibly themselves of compound nature. Hence, if we wish to speak of general laws of nature that are uniformly applicable to all bodies from the nebula to man we are left only with gravity and perhaps the most general form of the theory of the transformation of energy, vulgo the mechanical theory of heat. But, on its general, consistent application to all phenomena of nature, this theory itself becomes converted into a historical presentation of the successive changes occurring in a system of the universe from its origin to its passing away, hence into a history in which at each stage different laws, i.e., different phenomenal forms of the same universal motion, predominate, and so nothing remains as absolutely universally valid except motion. The geocentric standpoint in astronomy is prejudiced and has rightly been abolished. But as we go deeper in our investigations, it comes more and more into its own. The sun, etc., serve the earth (Hegel, Naturphilosophie, p. 155). (The whole huge sun exists merely for the sake of the little planets.) Anything other than geocentric physics, chemistry, biology, meteorology, etc., is impossible for us, and these sciences lose nothing by saying that they only hold good for the earth and are therefore only relative. If one takes that seriously and demands a centreless science, one puts a stop to all science. It suffices us to know that under the same conditions everywhere the same must take place, at a distance to the right or the left of us that is a million million times as great as the distance from the earth to the sun. Cognition. Ants have eyes different from ours, they can see chemical (?) light-rays (Nature, June 8, 1882, Lubbock), but as regards knowledge of these rays that are invisible to, us, we are considerably more advanced than the ants, and the very fact that we are able to demonstrate that ants can see things invisible to us, and that this proof is based solely on perceptions made with our eyes, shows that the special construction of the human eye sets no absolute barrier to human cognition. In addition to the eye, we have not only the other senses but also our thought activity. With regard to the latter, matters stand exactly as with the eye. To know what can be discovered by our thinking, it is no use, a hundred years after Kant, to try and find out the range of thought from the critique of reason or the investigation of the instrument of knowing. It is as little use as when Helmholtz uses the imperfection of our sight (indeed a necessary imperfection, for an eye that could see all rays would for that very reason see nothing at all), and the construction of our eye which restricts sight to definite limits and even so does not give quite correct reproduction as proof that the eye acquaints us incorrectly or unreliably with the nature of what is seen. What can be discovered by our thought is more evident from what it has already discovered and is every day still discovering. And that is already enough both as regards quantity and quality. On the other hand, the investigation of the forms of thought, the thought determinations, is very profitable and necessary, and since Aristotle this has been systematically undertaken only by Hegel. In any case we shall never And out how chemical rays appear to ants. Anyone who is distressed by this is simply beyond help. The form of development of natural science, in so far as it thinks, is the hypothesis. A new fact is observed which makes impossible the previous method of explaining the facts belonging to the same group. From this moment onwards new methods of explanation are required at first based on only a limited number of facts and observations. Further observational material weeds out these hypotheses, doing away with some and correcting others, until finally the law is established in a pure form. If one should wait until the material for a law was in a pure form, it would mean suspending the process of thought in investigation until then and, if only for this, reason, the law would never come into being. The number and succession of hypotheses supplanting one another given the lack of logical and dialectical education among natural scientists easily gives rise to the idea that we cannot know the essence of things (Haller and Goethe). This is not peculiar to natural science since all human knowledge develops in a much twisted curve; and in the historical sciences also, including philosophy, theories displace one another, from which, however, nobody concludes that formal logic, for instance, is nonsense. The last form of this outlook is the thing-in-itself In the first place, this assertion that we cannot know the thing-in-itself (Hegel, Enzyklopadie, paragraph 44) passes out of the realm of science into that of fantasy. Secondly, it does not add a word to our scientific knowledge, for if we cannot occupy ourselves with things, they do not exist for us. And, thirdly, it is a mere phrase and is never applied. Taken in the abstract it sounds quite sensible. But suppose one applies it. What would one think of a zoologist who said: A dog seems to have four legs, but we do not know whether in reality it has four million legs or none at all ? Or of a mathematician who first of all defines a triangle as having three sides, and then declares that he does not know whether it might not have 25? That 2 2 seems to be 4? But scientists take care not to apply the phrase about the thing-in-itself in natural science, they permit themselves this only in passing into philosophy. This is the best proof how little seriously they take it and what little value it has itself. If they did take it seriously, what would be the good of investigating anything? Taken historically the thing would have a certain meaning: we can only know under the conditions of our epoch and as far as these allow. The thing-in-itself: Hegel, Logik, II, p. 10, also later a whole section on it: Hegel, therefore, is here a much more resolute materialist than the modern natural scientists. Valuable self-criticism of the Kantian thing-in-itself, which shows that Kant suffers shipwreck also on the thinking ego and likewise discovers in it an unknowable thing-in-itself. (Hegel, V. p. 256 et seq.) 
Notes and Fragments. Dialectics of Nature