The volume before us  carries us back to a period which, although in time no more than a generation behind us, has become as foreign to the present generation in Germany as if it were already a hundred years old. Yet it was the period of Germany's preparation for the Revolution of 1848; and all that has happened since then in our country has been merely a continuation of 1848, merely the execution of the last will and testament of the revolution.
Just as in France in the 18th century, so in Germany in the 19th, a philosophical revolution ushered in the political collapse. But how different the two looked! The French were in open combat against all official science, against the church and often also against the state; their writings were printed across the frontier, in Holland or England, while they themselves were often in jeopardy of imprisonment in the Bastille. On the other hand, the Germans were professors, state-appointed instructors of youth; their writings were recognized textbooks, and the termination system of the whole development -- the Hegelian system -- was even raised, as it were, to the rank of a royal Prussian philosophy of state! Was it possible that a revolution could hide behind these professors, behind their obscure, pedantic phrases, their ponderous, wearisome sentences? Were not precisely these people who were then regarded as the representatives of the revolution, the liberals, the bitterest opponents of this brain-confusing philosophy? But what neither the government nor the liberals saw was seen at least by one man as early as 1833, and this man was indeed none other than Heinrich Heine. 
Let us take an example. No philosophical proposition has earned more gratitude from narrow-minded governments and wrath from equally narrow-minded liberals than Hegel's famous statement: "All that is real is rational; and all that is rational is real." That was tangibly a sanctification of things that be, a philosophical benediction bestowed upon despotism, police government, Star Chamber proceedings and censorship. That is how Frederick William III and how his subjects understood it. But according to Hegel certainly not everything that exists is also real, without further qualification. For Hegel the attribute of reality belongs only to that which at the same time is necessary: "In the course of its development reality proves to be necessity." A particular governmental measure -- Hegel himself cites the example of "a certain tax regulation" -- is therefore for him by no means real without qualification. That which is necessary, however, proves itself in the last resort to be also rational; and, applied to the Prussian state of that time, the Hegelian proposition, therefore, merely means: this state is rational, corresponds to reason, insofar as it is necessary; and if it nevertheless appears to us to be evil, but still, in spite of its evil character, continues to exist, then the evil character of the government is justified and explained by the corresponding evil character of its subjects. The Prussians of that day had the government that they deserved.
Now, according to Hegel, reality is, however, in no way an attribute predictable of any given state of affairs, social or political, in all circumstances and at all times. On the contrary. The Roman Republic was real, but so was the Roman Empire, which superseded it. In 1789, the French monarchy had become so unreal, that is to say, so robbed of all necessity, so irrational, that it had to be destroyed by the Great Revolution, of which Hegel always speaks with the greatest enthusiasm. In this case, therefore, the monarchy was the unreal and the revolution the real. And so, in the course of development, all that was previously real becomes unreal, loses it necessity, its right of existence, its rationality. And in the place of moribund reality comes a new, viable reality -- peacefully if the old has enough intelligence to go to its death without a struggle; forcibly if it resists this necessity. Thus the Hegelian proposition turns into its opposite through Hegelian dialectics itself: All that is real in the sphere of human history, becomes irrational in the process of time, is therefore irrational by its very destination, is tainted beforehand with irrationality, and everything which is rational in the minds of men is destined to become real, however much it may contradict existing apparent reality. In accordance with all the rules of the Hegelian method of thought, the proposition of the rationality of everything which is real resolves itself into the other proposition: All that exists deserves to perish.
But precisely therein lay the true significance and the revolutionary character of the Hegelian philosophy (to which, as the close of the whole movement since Kant, we must here confine ourselves), that it once and for all dealt the death blow to the finality of all product of human thought and action. Truth, the cognition of which is the business of philosophy, was in the hands of Hegel no longer an aggregate of finished dogmatic statements, which, once discovered, had merely to be learned by heart. Truth lay now in the process of cognition itself, in the long historical development of science, which mounts from lower to ever higher levels of knowledge without ever reaching, by discovering so-called absolute truth, a point at which it can proceed no further, where it would have nothing more to do than to fold its hands and gaze with wonder at the absolute truth to which it had attained. And what holds good for the realm of philosophical knowledge holds good also for that of every other kind of knowledge and also for practical action. Just as knowledge is unable to reach a complete conclusion in a perfect, ideal condition of humanity, so is history unable to do so; a perfect society, a perfect "state", are things which can only exist in imagination. On the contrary, all successive historical systems are only transitory stages in the endless course of development of human society from the lower to the higher. Each stage is necessary, and therefore justified for the time and conditions to which it owes its origin. But in the face of new, higher conditions which gradually develop in its own womb, it loses vitality and justification. It must give way to a higher stage which will also in its turn decay and perish. Just as the bourgeoisie by large-scale industry, competition, and the world market dissolves in practice all stable time-honored institutions, so this dialectical philosophy dissolves all conceptions of final, absolute truth and of absolute states of humanity corresponding to it. For it [dialectical philosophy], nothing is final, absolute, sacred. It reveals the transitory character of everything and in everything; nothing can endure before it except the uninterrupted process of becoming and of passing away, of endless ascendancy from the lower to the higher. And dialectical philosophy itself is nothing more than the mere reflection of this process in the thinking brain. It has, of course, also a conservative side; it recognizes that definite stages of knowledge and society are justified for their time and circumstances; but only so far. The conservatism of this mode of outlook is relative; its revolutionary character is absolute -- the only absolute dialectical philosophy admits.
It is not necessary, here, to go into the question of whether this mode of outlook is thoroughly in accord with the present state of natural science, which predicts a possible end even for the Earth, and for its habitability a fairly certain one; which therefore recognizes that for the history of mankind, too, there is not only an ascending but also a descending branch. At any rate, we still find ourselves a considerable distance from the turning-point at which the historical course of society becomes one of descent, and we cannot expect Hegelian philosophy to be concerned with a subject which natural science, in its time, had not at all placed upon the agenda as yet.
But what must, in fact, be said here is this: that in Hegel the views developed above are not so sharply delineated. They are a necessary conclusion from his method, but one which he himself never drew with such explicitness. And this, indeed, for the simple reason that he was compelled to make a system and, in accordance with traditional requirements, a system of philosophy must conclude with some sort of absolute truth. Therefore, however much Hegel, especially in his Logic, emphasized that this eternal truth is nothing but the logical, or, the historical, process itself, he nevertheless finds himself compelled to supply this process with an end, just because he has to bring his system to a termination at some point or other. In his Logic, he can make this end a beginning again, since here the point of the conclusion, the absolute idea -- which is only absolute insofar as he has absolutely nothing to say about it -- "alienates", that is, transforms, itself into nature and comes to itself again later in the mind, that is, in thought and in history. But at the end of the whole philosophy, a similar return to the beginning is possible only in one way. Namely, by conceiving of the end of history as follows: mankind arrives at the cognition of the self-same absolute idea, and declares that this cognition of the absolute idea is reached in Hegelian philosophy. In this way, however, the whole dogmatic content of the Hegelian system is declared to be absolute truth, in contradiction to his dialectical method, which dissolves all dogmatism. Thus the revolutionary side is smothered beneath the overgrowth of the conservative side. And what applies to philosophical cognition applies also to historical practice. Mankind, which, in the person of Hegel, has reached the point of working out the absolute idea, must also in practice have gotten so far that it can carry out this absolute idea in reality. Hence the practical political demands of the absolute idea on contemporaries may not be stretched too far. And so we find at the conclusion of the Philosophy of Right that the absolute idea is to be realized in that monarchy based on social estates which Frederick William III so persistently but vainly promised to his subjects, that is, in a limited, moderate, indirect rule of the possessing classes suited to the petty-bourgeois German conditions of that time; and, moreover, the necessity of the nobility is demonstrated to us in a speculative fashion.
The inner necessities of the system are, therefore, of themselves sufficient to explain why a thoroughly revolutionary method of thinking produced an extremely tame political conclusion. As a matter of fact, the specific form of this conclusion springs from this, that Hegel was a German, and like his contemporary Goethe had a bit of the philistine's queue dangling behind. Each of them was an Olympian Zeus in his own sphere, yet neither of them ever quite freed himself from German philistinism.
But all this did not prevent the Hegelian system from covering an incomparably greater domain than any earlier system, nor from developing in this domain a wealth of thought, which is astounding even today. The phenomenology of mind (which one may call a parallel of the embryology and palaeontology of the mind, a development of individual consciousness through its different stages, set in the form of an abbreviated reproduction of the stages through which the consciousness of man has passed in the course of history), logic, natural philosophy, philosophy of mind, and the latter worked out in its separate, historical subdivisions: philosophy of history, of right, of religion, history of philosophy, aesthetics, etc. -- in all these different historical fields Hegel labored to discover and demonstrate the pervading thread of development. And as he was not only a creative genius but also a man of encyclopaedic erudition, he played an epoch-making role in every sphere. It is self-evident that owing to the needs of the "system" he very often had to resort to those forced constructions about which his pigmy opponents make such a terrible fuss even today. But these constructions are only the frame and scaffolding of his work. If one does not loiter here needlessly, but presses on farther into the immense building, one finds innumerable treasures which today still possess undiminshed value. With all philosophers it is precisely the "system" which is perishable; and for the simple reason that it springs from an imperishable desire of the human mind -- the desire to overcome all contradictions. But if all contradictions are once and for all disposed of, we shall have arrived at so-called absolute truth -- world history will be at an end. And yet it has to continue, although there is nothing left for it to do -- hence, a new, insoluble contradiction. As soon as we have once realized -- and in the long run no one has helped us to realize it more than Hegel himself -- that the task of philosophy thus stated means nothing but the task that a single philosopher should accomplish that which can only be accomplished by the entire human race in its progressive development -- as soon as we realize that, there is an end to all philosophy in the hitherto accepted sense of the word. One leaves alone "absolute truth", which is unattainable along this path or by any single individual; instead, one pursues attainable relative truths along the path of the positive sciences, and the summation of their results by means of dialectical thinking. At any rate, with Hegel philosophy comes to an end; on the one hand, because in his system he summed up its whole development in the most splendid fashion; and on the other hand, because, even though unconsciously, he showed us the way out of the labyrinth of systems to real positive knowledge of the world.
One can imagine what a tremendous effect this Hegelian system must have produced in the philosophy-tinged atmosphere of Germany. It was a triumphant procession which lasted for decades and which by no means came to a standstill on the death of Hegel. On the contrary, it was precisely from 1830 to 1840 that "Hegelianism" reigned most exclusively, and to a greater or lesser extent infected even its opponents. It was precisely in this period that Hegelian views, consciously or unconsciously, most extensively penetrated the most diversified sciences and leavened even popular literature and the daily press, from which the average "educated consciousness" derives its mental pabulum. But this victory along the whole front was only the prelude to an internal struggle.
As we have seen, the doctrine of Hegel, taken as a whole, left plenty of room for giving shelter to the most diverse practical party views. And in the theoretical Germany of that time, two things above all were practical: religion and politics. Whoever placed the chief emphasis on the Hegelian system could be fairly conservative in both spheres; whoever regarded the dialectical method as the main thing could belong to the most extreme opposition, both in politics and religion. Hegel himself, despite the fairly frequent outbursts of revolutionary wrath in his works, seemed on the whole to be more inclined to the conservative side. Indeed, his system had cost him much more "hard mental plugging" than his method. Towards the end of the thirties, the cleavage in the school became more and more apparent. The Left wing, the so-called Young Hegelians, in their fight with the pietist orthodox and the feudal reactionaries, abandoned bit by bit that philosophical-genteel reserve in regard to the burning questions of the day which up to that time had secured state toleration and even protection for their teachings. And when in 1840, orthodox pietism and absolutist feudal reaction ascended the throne with Frederick William IV, open partisanship became unavoidable. The fight was still carried on with philosophical weapons, but no longer for abstract philosophical aims. It turned directly on the destruction of traditional religion and of the existing state. And while in the Deutsche Jahrbucher  the practical ends were still predominantly put forward in philosophical disguise, in the Rheinische Zeitung of 1842 the Young Hegelian school revealed itself directly as the philosophy of the aspiring radical bourgeoisie and used the meagre cloak of philosophy only to deceive the censorship.
At that time, however, politics was a very thorny field, and hence the main fight came to be directed against religion; this fight, particularly since 1840, was indirectly also political. Strauss' Life of Jesus, published in 1835, had provided the first impulse. The theory therein developed of the formation of the gospel myths was combated later by Bruno Bauer with proof that a whole series of evangelic stories had been fabricated by the authors themselves. The controversy between these two was carried out in the philosophical disguise of a battle between "self-consciousness" and "substance". The question whether the miracle stories of the gospels came into being through unconscious-traditional myth-creation within the bosom of the community or whether they were fabricated by the evangelists themselves was magnified into the question whether, in world history, "substance" or "self-consciousness" was the decisive operative force. Finally came Stirner, the prophet of contemporary anarchism -- Bakunin has taken a great deal from him -- and capped the sovereign "self-consciousness" by his sovereign "ego". 
We will not go further into this side of the decomposition process of the Hegelian school. More important for us is the following: the main body of the most determined Young Hegelians was, by the practical necessities of its fight against positive religion, driven back to Anglo-French materialism. This brought them into conflict with the system of their school. While materialism conceives nature as the sole reality, nature in the Hegelian system represents merely the "alienation" of the absolute idea, so to say, a degradation of the idea. At all events, thinking and its thought-product, the idea, is here the primary, nature the derivative, which only exists at all by the condescension of the idea. And in this contradiction they floundered as well or as ill as they could.
Then came Feuerbach's Essence of Christianity.  With one blow, it pulverized the contradiction, in that without circumlocutions it placed materialism on the throne again. Nature exists independently of all philosophy. It is the foundation upon which we human beings, ourselves products of nature, have grown up. Nothing exists outside nature and man, and the higher beings our religious fantasies have created are only the fantastic reflection of our own essence. The spell was broken; the "system" was exploded and cast aside, and the contradiction, shown to exist only in our imagination, was dissolved. One must himself have experienced the liberating effect of this book to get an idea of it. Enthusiasm was general; we all became at once Feuerbachians. How enthusiastically Marx greeted the new conception and how much -- in spite of all critical reservations -- he was influenced by it, one may read in the The Holy Family. 
Even the shortcomings of the book contributed to its immediate effect. Its literary, sometimes even high-flown, style secured for it a large public and was at any rate refreshing after long years of abstract and abstruse Hegelianizing. The same is true of its extravagant deification of love, which, coming after the now intolerable sovereign rule of "pure reason", had its excuse, if not justification. But what we must not forget is that it was precisely these two weaknesses of Feuerbach that "true Socialism", which had been spreading like a plague in educated Germany since 1844, took as its starting-point, putting literary phrases in the place of scientific knowledge, the liberation of mankind by means of "love" in place of the emancipation of the proletariat through the economic transformation of production -- in short, losing itself in the nauseous fine writing and ecstacies of love typified by Herr Karl Grun.
Another thing we must not forget is this: the Hegelian school disintegrated, but Hegelian philosophy was not overcome through criticism; Strauss and Bauer each took one of its sides and set it polemically against the other. Feuerbach smashed the system and simply discarded it. But a philosophy is not disposed of by the mere assertion that it is false. And so powerful a work as Hegelian philosophy, which had exercised so enormous an influence on the intellectual development of the nation, could not be disposed of by simply being ignored. It had to be "sublated" in its own sense, that is, in the sense that while its form had to be annihilated through criticism, the new content which had been won through it had to be saved. How this was brought about we shall see below.
But in the meantime, the Revolution of 1848 thrust the whole of philosophy aside as unceremoniously as Feuerbach had thrust aside Hegel. And in the process, Feuerbach himself was also pushed into the background.