Adapted from Marxists.org by Roderic Day.
Dialectical materialism is the world outlook of the Marxist-Leninist party. It is called dialectical materialism because its approach to the phenomena of nature, its method of studying and apprehending them, is dialectical, while its interpretation of the phenomena of nature, its conception of these phenomena, its theory, is materialistic.
Historical materialism is the extension of the principles of dialectical materialism to the study of social life, an application of the principles of dialectical materialism to the phenomena of the life of society, to the study of society and of its history.
When describing their dialectical method, Marx and Engels usually refer to Hegel as the philosopher who formulated the main features of dialectics. This, however, does not mean that the dialectics of Marx and Engels is identical with the dialectics of Hegel. As a matter of fact, Marx and Engels took from the Hegelian dialectics only its “rational kernel,” casting aside its Hegelian idealistic shell, and developed dialectics further so as to lend it a modern scientific form.
My dialectic method is not only different from the Hegelian, but is its direct opposite. To Hegel, … the process of thinking which, under the name of ‘the Idea,’ he even transforms into an independent subject, is the demiurgos (creator) of the real world, and the real world is only the external, phenomenal form of ‘the Idea.’ With me, on the contrary, the ideal is nothing else than the material world reflected by the human mind and translated into forms of thought. 
When describing their materialism, Marx and Engels usually refer to Feuerbach as the philosopher who restored materialism to its rights. This, however, does not mean that the materialism of Marx and Engels is identical with Feuerbach’s materialism. As a matter of fact, Marx and Engels took from Feuerbach’s materialism its “inner kernel,” developed it into a scientific-philosophical theory of materialism and cast aside its idealistic and religious-ethical encumbrances. We know that Feuerbach, although he was fundamentally a materialist, objected to the name materialism. Engels more than once declared that “in spite of” the materialist “foundation,” Feuerbach “remained… bound by the traditional idealist fetters,” and that “the real idealism of Feuerbach becomes evident as soon as we come to his philosophy of religion and ethics.” 
Dialectics comes from the Greek dialego, to discourse, to debate. In ancient times dialectics was the art of arriving at the truth by disclosing the contradictions in the argument of an opponent and overcoming these contradictions. There were philosophers in ancient times who believed that the disclosure of contradictions in thought and the clash of opposite opinions was the best method of arriving at the truth. This dialectical method of thought, later extended to the phenomena of nature, developed into the dialectical method of apprehending nature, which regards the phenomena of nature as being in constant movement and undergoing constant change, and the development of nature as the result of the development of the contradictions in nature, as the result of the interaction of opposed forces in nature.
In its essence, dialectics is the direct opposite of metaphysics.
The principal features of the Marxist dialectical method are as follows:
Nature Connected and Determined
Contrary to metaphysics, dialectics does not regard nature as an accidental agglomeration of things, of phenomena, unconnected with, isolated from, and independent of, each other, but as a connected and integral whole, in which things, phenomena are organically connected with, dependent on, and determined by, each other.
The dialectical method therefore holds that no phenomenon in nature can be understood if taken by itself, isolated from surrounding phenomena, inasmuch as any phenomenon in any realm of nature may become meaningless to us if it is not considered in connection with the surrounding conditions, but divorced from them; and that, vice versa, any phenomenon can be understood and explained if considered in its inseparable connection with surrounding phenomena, as one conditioned by surrounding phenomena.
Nature is a State of Continuous Motion and Change
Contrary to metaphysics, dialectics holds that nature is not a state of rest and immobility, stagnation and immutability, but a state of continuous movement and change, of continuous renewal and development, where something is always arising and developing, and something always disintegrating and dying away.
The dialectical method therefore requires that phenomena should be considered not only from the standpoint of their interconnection and interdependence, but also from the standpoint of their movement, their change, their development, their coming into being and going out of being.
The dialectical method regards as important primarily not that which at the given moment seems to be durable and yet is already beginning to die away, but that which is arising and developing, even though at the given moment it may appear to be not durable, for the dialectical method considers invincible only that which is arising and developing.
All nature, from the smallest thing to the biggest, from grains of sand to suns, from protista [the primary living cells — J. S.] to man, has its existence in eternal coming into being and going out of being, in a ceaseless flux, in unresting motion and change. 
Therefore, dialectics, Engels says, “takes things and their perceptual images essentially in their interconnection, in their concatenation, in their movement, in their rise and disappearance.” 
Natural Quantitative Change Leads to Qualitative Change
Contrary to metaphysics, dialectics does not regard the process of development as a simple process of growth, where quantitative changes do not lead to qualitative changes, but as a development which passes from insignificant and imperceptible quantitative changes to open ‘fundamental changes’ to qualitative changes; a development in which the qualitative changes occur not gradually, but rapidly and abruptly, taking the form of a leap from one state to another; they occur not accidentally but as the natural result of an accumulation of imperceptible and gradual quantitative changes.
The dialectical method therefore holds that the process of development should be understood not as movement in a circle, not as a simple repetition of what has already occurred, but as an onward and upward movement, as a transition from an old qualitative state to a new qualitative state, as a development from the simple to the complex, from the lower to the higher:
Nature is the test of dialectics, and it must be said for modern natural science that it has furnished extremely rich and daily increasing materials for this test, and has thus proved that in the last analysis nature’s process is dialectical and not metaphysical, that it does not move in an eternally uniform and constantly repeated circle, but passes through a real history. Here prime mention should be made of Darwin, who dealt a severe blow to the metaphysical conception of nature by proving that the organic world of today, plants and animals, and consequently man too, is all a product of a process of development that has been in progress for millions of years. 
Describing dialectical development as a transition from quantitative changes to qualitative changes, Engels says:
In physics … every change is a passing of quantity into quality, as a result of a quantitative change of some form of movement either inherent in a body or imparted to it. For example, the temperature of water has at first no effect on its liquid state; but as the temperature of liquid water rises or falls, a moment arrives when this state of cohesion changes and the water is converted in one case into steam and in the other into ice. … A definite minimum current is required to make a platinum wire glow; every metal has its melting temperature; every liquid has a definite freezing point and boiling point at a given pressure, as far as we are able with the means at our disposal to attain the required temperatures; finally, every gas has its critical point at which, by proper pressure and cooling, it can be converted into a liquid state. … What are known as the constants of physics [the point at which one state passes into another — J. S.] are in most cases nothing but designations for the nodal points at which a quantitative (change) increase or decrease of movement causes a qualitative change in the state of the given body, and at which, consequently, quantity is transformed into quality. 
Passing to chemistry, Engels continues:
Chemistry may be called the science of the qualitative changes which take place in bodies as the effect of changes of quantitative composition. This was already known to Hegel. … Take oxygen: if the molecule contains three atoms instead of the customary two, we get ozone, a body definitely distinct in odor and reaction from ordinary oxygen. And what shall we say of the different proportions in which oxygen combines with nitrogen or sulphur, and each of which produces a body qualitatively different from all other bodies! 
Finally, criticizing Dühring, who scolded Hegel for all he was worth, but surreptitiously borrowed from him the well-known thesis that the transition from the insentient world to the sentient world, from the kingdom of inorganic matter to the kingdom of organic life, is a leap to a new state, Engels says:
This is precisely the Hegelian nodal line of measure relations in which at certain definite nodal points, the purely quantitative increase or decrease gives rise to a qualitative leap, for example, in the case of water which is heated or cooled, where boiling point and freezing point are the nodes at which — under normal pressure — the leap to a new aggregate state takes place, and where consequently quantity is transformed into quality. 
Contradictions Inherent in Nature
Contrary to metaphysics, dialectics holds that internal contradictions are inherent in all things and phenomena of nature, for they all have their negative and positive sides, a past and a future, something dying away and something developing; and that the struggle between these opposites, the struggle between the old and the new, between that which is dying away and that which is being born, between that which is disappearing and that which is developing, constitutes the internal content of the process of development, the internal content of the transformation of quantitative changes into qualitative changes.
The dialectical method therefore holds that the process of development from the lower to the higher takes place not as a harmonious unfolding of phenomena, but as a disclosure of the contradictions inherent in things and phenomena, as a “struggle” of opposite tendencies which operate on the basis of these contradictions.
In its proper meaning dialectics is the study of the contradiction within the very essence of things. 
Development is the ‘struggle’ of opposites. 
Such, in brief, are the principal features of the Marxist dialectical method.
It is easy to understand how immensely important is the extension of the principles of the dialectical method to the study of social life and the history of society, and how immensely important is the application of these principles to the history of society and to the practical activities of the party of the proletariat.
If there are no isolated phenomena in the world, if all phenomena are interconnected and interdependent, then it is clear that every social system and every social movement in history must be evaluated not from the standpoint of “eternal justice” or some other preconceived idea, as is not infrequently done by historians, but from the standpoint of the conditions which gave rise to that system or that social movement and with which they are connected.
The slave system would be senseless, stupid and unnatural under modern conditions. But under the conditions of a disintegrating primitive communal system, the slave system is a quite understandable and natural phenomenon, since it represents an advance on the primitive communal system.
The demand for a bourgeois-democratic republic when tsardom and bourgeois society existed, as, let us say, in Russia in 1905, was a quite understandable, proper and revolutionary demand; for at that time a bourgeois republic would have meant a step forward. But now, under the conditions of the U.S.S.R., the demand for a bourgeois-democratic republic would be a senseless and counterrevolutionary demand; for a bourgeois republic would be a retrograde step compared with the Soviet republic.
Everything depends on the conditions, time and place.
It is clear that without such a historical approach to social phenomena, the existence and development of the science of history is impossible; for only such an approach saves the science of history from becoming a jumble of accidents and an agglomeration of most absurd mistakes.
Further, if the world is in a state of constant movement and development, if the dying away of the old and the upgrowth of the new is a law of development, then it is clear that there can be no “immutable” social systems, no “eternal principles” of private property and exploitation, no “eternal ideas” of the subjugation of the peasant to the landlord, of the worker to the capitalist.
Hence, the capitalist system can be replaced by the socialist system, just as at one time the feudal system was replaced by the capitalist system.
Hence, we must not base our orientation on the strata of society which are no longer developing, even though they at present constitute the predominant force, but on those strata which are developing and have a future before them, even though they at present do not constitute the predominant force.
In the eighties of the past century, in the period of the struggle between the Marxists and the Narodniks, the proletariat in Russia constituted an insignificant minority of the population, whereas the individual peasants constituted the vast majority of the population. But the proletariat was developing as a class, whereas the peasantry as a class was disintegrating. And just because the proletariat was developing as a class the Marxists based their orientation on the proletariat. And they were not mistaken; for, as we know, the proletariat subsequently grew from an insignificant force into a first-rate historical and political force.
Hence, in order not to err in policy, one must look forward, not backward.
Further, if the passing of slow quantitative changes into rapid and abrupt qualitative changes is a law of development, then it is clear that revolutions made by oppressed classes are a quite natural and inevitable phenomenon.
Hence, the transition from capitalism to socialism and the liberation of the working class from the yoke of capitalism cannot be effected by slow changes, by reforms, but only by a qualitative change of the capitalist system, by revolution.
Hence, in order not to err in policy, one must be a revolutionary, not a reformist.
Further, if development proceeds by way of the disclosure of internal contradictions, by way of collisions between opposite forces on the basis of these contradictions and so as to overcome these contradictions, then it is clear that the class struggle of the proletariat is a quite natural and inevitable phenomenon.
Hence, we must not cover up the contradictions of the capitalist system, but disclose and unravel them; we must not try to check the class struggle but carry it to its conclusion.
Hence, in order not to err in policy, one must pursue an uncompromising proletarian class policy, not a reformist policy of harmony of the interests of the proletariat and the bourgeoisie, not a compromisers’ policy of the “growing” of capitalism into socialism.
Such is the Marxist dialectical method when applied to social life, to the history of society.
As to Marxist philosophical materialism, it is fundamentally the direct opposite of philosophical idealism.
The principal features of Marxist philosophical materialism are as follows:
Contrary to idealism, which regards the world as the embodiment of an “absolute idea,” a “universal spirit,” “consciousness,” Marx’s philosophical materialism holds that the world is by its very nature material, that the multifold phenomena of the world constitute different forms of matter in motion, that interconnection and interdependence of phenomena as established by the dialectical method, are a law of the development of moving matter, and that the world develops in accordance with the laws of movement of matter and stands in no need of a “universal spirit.”
The materialistic outlook on nature means no more than simply conceiving nature just as it exists, without any foreign admixture. 
Speaking of the materialist views of the ancient philosopher Heraclitus, who held that “the world, the all in one, was not created by any god or any man, but was, is and ever will be a living flame, systematically flaring up and systematically dying down” Lenin comments: “A very good exposition of the rudiments of dialectical materialism.” 
Contrary to idealism, which asserts that only our consciousness really exists, and that the material world, being, nature, exists only in our consciousness, in our sensations, ideas and perceptions, the Marxist philosophical materialism holds that matter, nature, being, is an objective reality existing outside and independent of our consciousness; that matter is primary, since it is the source of sensations, ideas, consciousness, and that consciousness is secondary, derivative, since it is a reflection of matter, a reflection of being; that thought is a product of matter which in its development has reached a high degree of perfection, namely, of the brain, and the brain is the organ of thought; and that therefore one cannot separate thought from matter without committing a grave error. Engels says:
The question of the relation of thinking to being, the relation of spirit to nature is the paramount question of the whole of philosophy. … The answers which the philosophers gave to this question split them into two great camps. Those who asserted the primacy of spirit to nature … comprised the camp of idealism. The others, who regarded nature as primary, belong to the various schools of materialism. 
The material, sensuously perceptible world to which we ourselves belong is the only reality. … Our consciousness and thinking, however supra-sensuous they may seem, are the product of a material, bodily organ, the brain. Matter is not a product of mind, but mind itself is merely the highest product of matter. 
Concerning the question of matter and thought, Marx says:
It is impossible to separate thought from matter that thinks. Matter is the subject of all changes. 
Describing Marxist philosophical materialism, Lenin says:
Materialism in general recognizes objectively real being (matter) as independent of consciousness, sensation, experience. … Consciousness is only the reflection of being, at best an approximately true (adequate, perfectly exact) reflection of it. 
Matter is that which, acting upon our sense-organs, produces sensation; matter is the objective reality given to us in sensation. … Matter, nature, being — the physical — is primary, and spirit, consciousness, sensation — the psychical — is secondary. 
The world picture is a picture of how matter moves and of how ‘matter thinks.‘ 
The brain is the organ of thought. 
The World and Its Laws Are Knowable
Contrary to idealism, which denies the possibility of knowing the world and its laws, which does not believe in the authenticity of our knowledge, does not recognize objective truth, and holds that the world is full of “things-in-themselves” that can never be known to science, Marxist philosophical materialism holds that the world and its laws are fully knowable, that our knowledge of the laws of nature, tested by experiment and practice, is authentic knowledge having the validity of objective truth, and that there are no things in the world which are unknowable, but only things which are as yet not known, but which will be disclosed and made known by the efforts of science and practice.
Criticizing the thesis of Kant and other idealists that the world is unknowable and that there are “things-in-themselves” which are unknowable, and defending the well-known materialist thesis that our knowledge is authentic knowledge, Engels writes:
The most telling refutation of this as of all other philosophical crotchets is practice, namely, experiment and industry. If we are able to prove the correctness of our conception of a natural process by making it ourselves, bringing it into being out of its conditions and making it serve our own purposes into the bargain, then there is an end to the Kantian ungraspable ‘thing-in-itself.’ The chemical substances produced in the bodies of plants and animals remained such ‘things-in-themselves’ until organic chemistry began to produce them one after another, whereupon the ‘thing-in-itself’ became a thing for us, as, for instance, alizarin, the coloring matter of the madder, which we no longer trouble to grow ill the madder roots in the field, but produce much more cheaply and simply from coal tar. For 300 years the Copernican solar system was a hypothesis with a hundred, a thousand or ten thousand chances to one in its favor, but still always a hypothesis. But when Leverrier, by means of the data provided by this system, not only deduced the necessity of the existence of an unknown planet, but also calculated the position in the heavens which this planet must necessarily occupy, and when Galle really found this planet, the Copernican system was proved. 
Accusing Bogdanov, Bazarov, Yushkevich and the other followers of Mach of fideism (a reactionary theory, which prefers faith to science) and defending the well-known materialist thesis that our scientific knowledge of the laws of nature is authentic knowledge, and that the laws of science represent objective truth, Lenin says:
Contemporary fideism does not at all reject science; all it rejects is the ‘exaggerated claims’ of science, to wit, its claim to objective truth. If objective truth exists (as the materialists think), if natural science, reflecting the outer world in human ‘experience,’ is alone capable of giving us objective truth, then all fideism is absolutely refuted. 
Such, in brief, are the characteristic features of the Marxist philosophical materialism.
It is easy to understand how immensely important is the extension of the principles of philosophical materialism to the study of social life, of the history of society, and how immensely important is the application of these principles to the history of society and to the practical activities of the party of the proletariat.
If the connection between the phenomena of nature and their interdependence are laws of the development of nature, it follows, too, that the connection and interdependence of the phenomena of social life are laws of the development of society, and not something accidental.
Hence, social life, the history of society, ceases to be an agglomeration of “accidents,” for the history of society becomes a development of society according to regular laws, and the study of the history of society becomes a science.
Hence, the practical activity of the party of the proletariat must not be based on the good wishes of “outstanding individuals,” not on the dictates of “reason,” “universal morals,” etc., but on the laws of development of society and on the study of these laws.
Further, if the world is knowable and our knowledge of the laws of development of nature is authentic knowledge, having the validity of objective truth, it follows that social life, the development of society, is also knowable, and that the data of science regarding the laws of development of society are authentic data having the validity of objective truths.
Hence, the science of the history of society, despite all the complexity of the phenomena of social life, can become as precise a science as, let us say, biology, and capable of making use of the laws of development of society for practical purposes.
Hence, the party of the proletariat should not guide itself in its practical activity by casual motives, but by the laws of development of society, and by practical deductions from these laws.
Hence, socialism is converted from a dream of a better future for humanity into a science.
Hence, the bond between science and practical activity, between theory and practice, their unity, should be the guiding star of the party of the proletariat.
Further, if nature, being, the material world, is primary, and consciousness, thought, is secondary, derivative; if the material world represents objective reality existing independently of the consciousness of men, while consciousness is a reflection of this objective reality, it follows that the material life of society, its being, is also primary, and its spiritual life secondary, derivative, and that the material life of society is an objective reality existing independently of the will of men, while the spiritual life of society is a reflection of this objective reality, a reflection of being.
Hence, the source of formation of the spiritual life of society, the origin of social ideas, social theories, political views and political institutions, should not be sought for in the ideas, theories, views and political institutions themselves, but in the conditions of the material life of society, in social being, of which these ideas, theories, views, etc., are the reflection.
Hence, if in different periods of the history of society different social ideas, theories, views and political institutions are to be observed; if under the slave system we encounter certain social ideas, theories, views and political institutions, under feudalism others, and under capitalism others still, this is not to be explained by the “nature,” the “properties” of the ideas, theories, views and political institutions themselves but by the different conditions of the material life of society at different periods of social development.
Whatever is the being of a society, whatever are the conditions of material life of a society, such are the ideas, theories, political views and political institutions of that society.
In this connection, Marx says:
It is not the consciousness of men that determines their being, but, on the contrary, their social being that determines their consciousness. 
Hence, in order not to err in policy, in order not to find itself in the position of idle dreamers, the party of the proletariat must not base its activities on abstract “principles of human reason,” but on the concrete conditions of the material life of society, as the determining force of social development; not on the good wishes of “great men,” but on the real needs of development of the material life of society.
The fall of the utopians, including the Narodniks, anarchists and Socialist-Revolutionaries, was due, among other things, to the fact that they did not recognize the primary role which the conditions of the material life of society play in the development of society, and, sinking to idealism, did not base their practical activities on the needs of the development of the material life of society, but, independently of and in spite of these needs, on “ideal plans” and “all-embracing projects,” divorced from the real life of society.
The strength and vitality of Marxism-Leninism lies in the fact that it does base its practical activity on the needs of the development of the material life of society and never divorces itself from the real life of society.
It does not follow from Marx’s words, however, that social ideas, theories, political views and political institutions are of no significance in the life of society, that they do not reciprocally affect social being, the development of the material conditions of the life of society. We have been speaking so far of the origin of social ideas, theories, views and political institutions, of the way they arise, of the fact that the spiritual life of society is a reflection of the conditions of its material life. As regards the significance of social ideas, theories, views and political institutions, as regards their role in history, historical materialism, far from denying them, stresses the important role and significance of these factors in the life of society, in its history.
There are different kinds of social ideas and theories. There are old ideas and theories which have outlived their day and which serve the interests of the moribund forces of society. Their significance lies in the fact that they hamper the development, the progress of society. Then there are new and advanced ideas and theories which serve the interests of the advanced forces of society. Their significance lies in the fact that they facilitate the development, the progress of society; and their significance is the greater the more accurately they reflect the needs of development of the material life of society.
New social ideas and theories arise only after the development of the material life of society has set new tasks before society. But once they have arisen they become a most potent force which facilitates the carrying out of the new tasks set by the development of the material life of society, a force which facilitates the progress of society. It is precisely here that the tremendous organizing, mobilizing and transforming value of new ideas, new theories, new political views and new political institutions manifests itself. New social ideas and theories arise precisely because they are necessary to society, because it is impossible to carry out the urgent tasks of development of the material life of society without their organizing, mobilizing and transforming action. Arising out of the new tasks set by the development of the material life of society, the new social ideas and theories force their way through, become the possession of the masses, mobilize and organize them against the moribund forces of society, and thus facilitate the overthrow of these forces, which hamper the development of the material life of society.
Thus social ideas, theories and political institutions, having arisen on the basis of the urgent tasks of the development of the material life of society, the development of social being, themselves then react upon social being, upon the material life of society, creating the conditions necessary for completely carrying out the urgent tasks of the material life of society, and for rendering its further development possible.
In this connection, Marx says:
Theory becomes a material force as soon as it has gripped the masses. 
Hence, in order to be able to influence the conditions of material life of society and to accelerate their development and their improvement, the party of the proletariat must rely upon such a social theory, such a social idea as correctly reflects the needs of development of the material life of society, and which is therefore capable of setting into motion broad masses of the people and of mobilizing them and organizing them into a great army of the proletarian party, prepared to smash the reactionary forces and to clear the way for the advanced forces of society.
The fall of the “Economists” and the Mensheviks was due, among other things, to the fact that they did not recognize the mobilizing, organizing and transforming role of advanced theory, of advanced ideas and, sinking to vulgar materialism, reduced the role of these factors almost to nothing, thus condemning the Party to passivity and inanition.
The strength and vitality of Marxism-Leninism is derived from the fact that it relies upon an advanced theory which correctly reflects the needs of development of the material life of society, that it elevates theory to a proper level, and that it deems it its duty to utilize every ounce of the mobilizing, organizing and transforming power of this theory.
That is the answer historical materialism gives to the question of the relation between social being and social consciousness, between the conditions of development of material life and the development of the spiritual life of society.
It now remains to elucidate the following question: What, from the viewpoint of historical materialism, is meant by the “conditions of material life of society” which in the final analysis determine the physiognomy of society, its ideas, views, political institutions, etc.?
What, after all, are these “conditions of material life of society,” what are their distinguishing features?
There can be no doubt that the concept “conditions of material life of society” includes, first of all, nature which surrounds society, geographical environment, which is one of the indispensable and constant conditions of material life of society and which, of course, influences the development of society. What role does geographical environment play in the development of society? Is geographical environment the chief force determining the physiognomy of society, the character of the social system of man, the transition from one system to another, or isn’t it?
Historical materialism answers this question in the negative.
Geographical environment is unquestionably one of the constant and indispensable conditions of development of society and, of course, influences the development of society, accelerates or retards its development. But its influence is not the determining influence, inasmuch as the changes and development of society proceed at an incomparably faster rate than the changes and development of geographical environment. In the space of 3,000 years three different social systems have been successively superseded in Europe: the primitive communal system, the slave system and the feudal system. In the eastern part of Europe, in the U.S.S.R., even four social systems have been superseded. Yet during this period geographical conditions in Europe have either not changed at all, or have changed so slightly that geography takes no note of them. And that is quite natural. Changes in geographical environment of any importance require millions of years, whereas a few hundred or a couple of thousand years are enough for even very important changes in the system of human society.
It follows from this that geographical environment cannot be the chief cause, the determining cause of social development; for that which remains almost unchanged in the course of tens of thousands of years cannot be the chief cause of development of that which undergoes fundamental changes in the course of a few hundred years.
Further, there can be no doubt that the concept “conditions of material life of society” also includes growth of population, density of population of one degree or another; for people are an essential element of the conditions of material life of society, and without a definite minimum number of people there can be no material life of society. Is growth of population the chief force that determines the character of the social system of man, or isn’t it?
Historical materialism answers this question too in the negative.
Of course, growth of population does influence the development of society, does facilitate or retard the development of society, but it cannot be the chief force of development of society, and its influence on the development of society cannot be the determining influence because, by itself, growth of population does not furnish the clue to the question why a given social system is replaced precisely by such and such a new system and not by another, why the primitive communal system is succeeded precisely by the slave system, the slave system by the feudal system, and the feudal system by the bourgeois system, and not by some other.
If growth of population were the determining force of social development, then a higher density of population would be bound to give rise to a correspondingly higher type of social system. But we do not find this to be the case. The density of population in China is four times as great as in the U.S.A., yet the U.S.A. stands higher than China in the scale of social development; for in China a semi-feudal system still prevails, whereas the U.S.A. has long ago reached the highest stage of development of capitalism. The density of population in Belgium is 19 times as great as in the U.S.A., and 26 times as great as in the U.S.S.R. Yet the U.S.A. stands higher than Belgium in the scale of social development; and as for the U.S.S.R., Belgium lags a whole historical epoch behind this country, for in Belgium the capitalist system prevails, whereas the U.S.S.R. has already done away with capitalism and has set up a socialist system.
It follows from this that growth of population is not, and cannot be, the chief force of development of society, the force which determines the character of the social system, the physiognomy of society.
What Is the Chief Determinant Force?
What, then, is the chief force in the complex of conditions of material life of society which determines the physiognomy of society, the character of the social system, the development of society from one system to another?
This force, historical materialism holds, is the method of procuring the means of life necessary for human existence, the mode of production of material values — food, clothing, footwear, houses, fuel, instruments of production, etc. — which are indispensable for the life and development of society.
In order to live, people must have food, clothing, footwear, shelter, fuel, etc.; in order to have these material values, people must produce them; and in order to produce them, people must have the instruments of production with which food, clothing, footwear, shelter, fuel, etc., are produced, they must be able to produce these instruments and to use them.
The instruments of production wherewith material values are produced, the people who operate the instruments of production and carry on the production of material values thanks to a certain production experience and labor skill — all these elements jointly constitute the productive forces of society.
But the productive forces are only one aspect of production, only one aspect of the mode of production, an aspect that expresses the relation of men to the objects and forces of nature which they make use of for the production of material values. Another aspect of production, another aspect of the mode of production, is the relation of men to each other in the process of production, men’s relations of production. Men carry on a struggle against nature and utilize nature for the production of material values not in isolation from each other, not as separate individuals, but in common, in groups, in societies. Production, therefore, is at all times and under all conditions social production. In the production of material values men enter into mutual relations of one kind or another within production, into relations of production of one kind or another. These may be relations of co-operation and mutual help between people who are free from exploitation; they may be relations of domination and subordination; and, lastly, they may be transitional from one form of relations of production to another. But whatever the character of the relations of production may be, always and in every system they constitute just as essential an element of production as the productive forces of society.
In production men not only act on nature but also on one another. They produce only by co-operating in a certain way and mutually exchanging their activities. In order to produce, they enter into definite connections and relations with one another and only within these social connections and relations does their action on nature, does production, take place. 
Consequently, production, the mode of production, embraces both the productive forces of society and men’s relations of production, and is thus the embodiment of their unity in the process of production of material values.
The First Feature of Production
The first feature of production is that it never stays at one point for a long time and is always in a state of change and development, and that, furthermore, changes in the mode of production inevitably call forth changes in the whole social system, social ideas, political views and political institutions — they call forth a reconstruction of the whole social and political order. At different stages of development people make use of different modes of production, or, to put it more crudely, lead different manners of life. In the primitive commune there is one mode of production, under slavery there is another mode of production, under feudalism a third mode of production and so on. And, correspondingly, men’s social system, the spiritual life of men, their views and political institutions also vary.
Whatever is the mode of production of a society, such in the main is the society itself, its ideas and theories, its political views and institutions.
Or, to put it more crudely, whatever is man’s manner of life such is his manner of thought.
This means that the history of development of society is above all the history of the development of production, the history of the modes of production which succeed each other in the course of centuries, the history of the development of productive forces and of people’s relations of production.
Hence, the history of social development is at the same time the history of the producers of material values themselves, the history of the laboring masses, who are the chief force in the process of production and who carry on the production of material values necessary for the existence of society.
Hence, if historical science is to be a real science, it can no longer reduce the history of social development to the actions of kings and generals, to the actions of “conquerors” and “subjugators” of states, but must above all devote itself to the history of the producers of material values, the history of the laboring masses, the history of peoples.
Hence, the clue to the study of the laws of history of society must not be sought in men’s minds, in the views and ideas of society, but in the mode of production practiced by society in any given historical period; it must be sought in the economic life of society.
Hence, the prime task of historical science is to study and disclose the laws of production, the laws of development of the productive forces and of the relations of production, the laws of economic development of society.
Hence, if the party of the proletariat is to be a real party, it must above all acquire a knowledge of the laws of development of production, of the laws of economic development of society.
Hence, if it is not to err in policy, the party of the proletariat must both in drafting its program and in its practical activities proceed primarily from the laws of development of production from the laws of economic development of society.
The Second Feature of Production
The second feature of production is that its changes and development always begin with changes and development of the productive forces, and in the first place, with changes and development of the instruments of production. Productive forces are therefore the most mobile and revolutionary element of production. First the productive forces of society change and develop, and then, depending on these changes and in conformity with them, men’s relations of production, their economic relations, change. This, however, does not mean that the relations of production do not influence the development of the productive forces and that the latter are not dependent on the former. While their development is dependent on the development of the productive forces, the relations of production in their turn react upon the development of the productive forces, accelerating or retarding it. In this connection it should be noted that the relations of production cannot for too long a time lag behind and be in a state of contradiction to the growth of the productive forces, inasmuch as the productive forces can develop in full measure only when the relations of production correspond to the character, the state of the productive forces and allow full scope for their development. Therefore, however much the relations of production may lag behind the development of the productive forces, they must, sooner or later, come into correspondence with — and actually do come into correspondence with — the level of development of the productive forces, the character of the productive forces. Otherwise we would have a fundamental violation of the unity of the productive forces and the relations of production within the system of production, a disruption of production as a whole, a crisis of production, a destruction of productive forces.
An instance in which the relations of production do not correspond to the character of the productive forces, conflict with them, is the economic crises in capitalist countries, where private capitalist ownership of the means of production is in glaring incongruity with the social character of the process of production, with the character of the productive forces. This results in economic crises, which lead to the destruction of productive forces. Furthermore, this incongruity itself constitutes the economic basis of social revolution, the purpose of which is to destroy the existing relations of production and to create new relations of production corresponding to the character of the productive forces.
In contrast, an instance in which the relations of production completely correspond to the character of the productive forces is the socialist national economy of the U.S.S.R., where the social ownership of the means of production fully corresponds to the social character of the process of production, and where, because of this, economic crises and the destruction of productive forces are unknown.
Consequently, the productive forces are not only the most mobile and revolutionary element in production, but are also the determining element in the development of production.
Whatever are the productive forces, such must be the relations of production.
While the state of the productive forces furnishes the answer to the question — with what instruments of production do men produce the material values they need? — the state of the relations of production furnishes the answer to another question — who owns the means of production (the land, forests, waters, mineral resources, raw materials, instruments of production, production premises, means of transportation and communication, etc.), who commands the means of production, whether the whole of society, or individual persons, groups, or classes which utilize them for the exploitation of other persons, groups or classes?
Here is a rough picture of the development of productive forces from ancient times to our day. The transition from crude stone tools to the bow and arrow, and the accompanying transition from the life of hunters to the domestication of animals and primitive pasturage; the transition from stone tools to metal tools (the iron axe, the wooden plow fitted with an iron coulter, etc.), with a corresponding transition to tillage and agriculture; a further improvement in metal tools for the working up of materials, the introduction of the blacksmith’s bellows, the introduction of pottery, with a corresponding development of handicrafts, the separation of handicrafts from agriculture, the development of an independent handicraft industry and, subsequently, of manufacture; the transition from handicraft tools to machines and the transformation of handicraft and manufacture into machine industry; the transition to the machine system and the rise of modern large-scale machine industry — such is a general and far from complete picture of the development of the productive forces of society in the course of man’s history. It will be clear that the development and improvement of the instruments of production was effected by men who were related to production, and not independently of men; and, consequently, the change and development of the instruments of production was accompanied by a change and development of men, as the most important element of the productive forces, by a change and development of their production experience, their labor skill, their ability to handle the instruments of production.
In conformity with the change and development of the productive forces of society in the course of history, men’s relations of production, their economic relations also changed and developed.
Main types of Relations of Production
Five main types of relations of production are known to history: primitive communal, slave, feudal, capitalist, and socialist.
The basis of the relations of production under the primitive communal system is that the means of production are socially owned. This in the main corresponds to the character of the productive forces of that period. Stone tools, and, later, the bow and arrow, precluded the possibility of men individually combating the forces of nature and beasts of prey. In order to gather the fruits of the forest, to catch fish, to build some sort of habitation, men were obliged to work in common if they did not want to die of starvation, or fall victim to beasts of prey or to neighboring societies. Labor in common led to the common ownership of the means of production, as well as of the fruits of production. Here the conception of private ownership of the means of production did not yet exist, except for the personal ownership of certain implements of production which were at the same time means of defense against beasts of prey. Here there was no exploitation, no classes.
The basis of the relations of production under the slave system is that the slave-owner owns the means of production, he also owns the worker in production — the slave, whom he can sell, purchase, or kill as though he were an animal. Such relations of production in the main correspond to the state of the productive forces of that period. Instead of stone tools, men now have metal tools at their command; instead of the wretched and primitive husbandry of the hunter, who knew neither pasturage nor tillage, there now appear pasturage tillage, handicrafts, and a division of labor between these branches of production. There appears the possibility of the exchange of products between individuals and between societies, of the accumulation of wealth in the hands of a few, the actual accumulation of the means of production in the hands of a minority, and the possibility of subjugation of the majority by a minority and the conversion of the majority into slaves. Here we no longer find the common and free labor of all members of society in the production process — here there prevails the forced labor of slaves, who are exploited by the non-laboring slave-owners. Here, therefore, there is no common ownership of the means of production or of the fruits of production. It is replaced by private ownership. Here the slaveowner appears as the prime and principal property owner in the full sense of the term.
Rich and poor, exploiters and exploited, people with full rights and people with no rights, and a fierce class struggle between them — such is the picture of the slave system.
The basis of the relations of production under the feudal system is that the feudal lord owns the means of production and does not fully own the worker in production — the serf, whom the feudal lord can no longer kill, but whom he can buy and sell. Alongside of feudal ownership there exists individual ownership by the peasant and the handicraftsman of his implements of production and his private enterprise based on his personal labor. Such relations of production in the main correspond to the state of the productive forces of that period. Further improvements in the smelting and working of iron; the spread of the iron plow and the loom; the further development of agriculture, horticulture, viniculture and dairying; the appearance of manufactories alongside of the handicraft workshops — such are the characteristic features of the state of the productive forces.
The new productive forces demand that the laborer shall display some kind of initiative in production and an inclination for work, an interest in work. The feudal lord therefore discards the slave, as a laborer who has no interest in work and is entirely without initiative, and prefers to deal with the serf, who has his own husbandry, implements of production, and a certain interest in work essential for the cultivation of the land and for the payment in kind of a part of his harvest to the feudal lord.
Here private ownership is further developed. Exploitation is nearly as severe as it was under slavery — it is only slightly mitigated. A class struggle between exploiters and exploited is the principal feature of the feudal system.
The basis of the relations of production under the capitalist system is that the capitalist owns the means of production, but not the workers in production — the wage laborers, whom the capitalist can neither kill nor sell because they are personally free, but who are deprived of means of production and in order not to die of hunger, are obliged to sell their labor power to the capitalist and to bear the yoke of exploitation. Alongside of capitalist property in the means of production, we find, at first on a wide scale, private property of the peasants and handicraftsmen in the means of production, these peasants and handicraftsmen no longer being serfs, and their private property being based on personal labor. In place of the handicraft workshops and manufactories there appear huge mills and factories equipped with machinery. In place of the manorial estates tilled by the primitive implements of production of the peasant, there now appear large capitalist farms run on scientific lines and supplied with agricultural machinery.
The new productive forces require that the workers in production shall be better educated and more intelligent than the downtrodden and ignorant serfs, that they be able to understand machinery and operate it properly. Therefore, the capitalists prefer to deal with wage-workers, who are free from the bonds of serfdom and who are educated enough to be able properly to operate machinery.
But having developed productive forces to a tremendous extent, capitalism has become enmeshed in contradictions which it is unable to solve. By producing larger and larger quantities of commodities, and reducing their prices, capitalism intensifies competition, ruins the mass of small and medium private owners, converts them into proletarians and reduces their purchasing power, with the result that it becomes impossible to dispose of the commodities produced. On the other hand, by expanding production and concentrating millions of workers in huge mills and factories, capitalism lends the process of production a social character and thus undermines its own foundation, inasmuch as the social character of the process of production demands the social ownership of the means of production; yet the means of production remain private capitalist property, which is incompatible with the social character of the process of production.
These irreconcilable contradictions between the character of the productive forces and the relations of production make themselves felt in periodical crises of over-production, when the capitalists, finding no effective demand for their goods owing to the ruin of the mass of the population which they themselves have brought about, are compelled to burn products, destroy manufactured goods, suspend production, and destroy productive forces at a time when millions of people are forced to suffer unemployment and starvation, not because there are not enough goods, but because there is an overproduction of goods.
This means that the capitalist relations of production have ceased to correspond to the state of productive forces of society and have come into irreconcilable contradiction with them.
This means that capitalism is pregnant with revolution, whose mission it is to replace the existing capitalist ownership of the means of production by socialist ownership.
This means that the main feature of the capitalist system is a most acute class struggle between the exploiters and the exploited.
The basis of the relations of production under the socialist system, which so far has been established only in the U.S.S.R., is the social ownership of the means of production. Here there are no longer exploiters and exploited. The goods produced are distributed according to labor performed, on the principle: “He who does not work, neither shall he eat.” Here the mutual relations of people in the process of production are marked by comradely cooperation and the socialist mutual assistance of workers who are free from exploitation. Here the relations of production fully correspond to the state of productive forces; for the social character of the process of production is reinforced by the social ownership of the means of production.
For this reason socialist production in the U.S.S.R. knows no periodical crises of over-production and their accompanying absurdities.
For this reason, the productive forces here develop at an accelerated pace; for the relations of production that correspond to them offer full scope for such development.
Such is the picture of the development of men’s relations of production in the course of human history.
Such is the dependence of the development of the relations of production on the development of the productive forces of society, and primarily, on the development of the instruments of production, the dependence by virtue of which the changes and development of the productive forces sooner or later lead to corresponding changes and development of the relations of production.
The use and fabrication of instruments of labor, although existing in the germ among certain species of animals, is specifically characteristic of the human labor-process, and Franklin therefore defines man as a tool-making animal. Relics of bygone instruments of labor possess the same importance for the investigation of extinct economical forms of society, as do fossil bones for the determination of extinct species of animals. It is not the articles made, but how they are made that enables us to distinguish different economical epochs. Instruments of labor not only supply a standard of the degree of development to which human labor has attained, but they are also indicators of the social conditions under which that labor is carried on. 
Social relations are closely bound up with productive forces. In acquiring new productive forces men change their mode of production; and in changing their mode of production, in changing the way of earning their living, they change all their social relations. The hand-mill gives you society with the feudal lord; the steam-mill, society with the industrial capitalist. 
There is a continual movement of growth in productive forces, of destruction in social relations, of formation in ideas; the only immutable thing is the abstraction of movement. 
Speaking of historical materialism as formulated in The Communist Manifesto, Engels says:
Economic production and the structure of society of every historical epoch necessarily arising therefrom constitute the foundation for the political and intellectual history of that epoch; … consequently (ever since the dissolution of the primeval communal ownership of land) all history has been a history of class struggles, of struggles between exploited and exploiting, between dominated and dominating classes at various stages of social development; … this struggle, however, has now reached a stage where the exploited and oppressed class (the proletariat) can no longer emancipate itself from the class which exploits and oppresses it (the bourgeoisie), without at the same time for ever freeing the whole of society from exploitation, oppression and class struggles… 
The Third Feature of Production
The third feature of production is that the rise of new productive forces and of the relations of production corresponding to them does not take place separately from the old system, after the disappearance of the old system, but within the old system; it takes place not as a result of the deliberate and conscious activity of man, but spontaneously, unconsciously, independently of the will of man. It takes place spontaneously and independently of the will of man for two reasons.
Firstly, because men are not free to choose one mode of production or another, because as every new generation enters life it finds productive forces and relations of production already existing as the result of the work of former generations, owing to which it is obliged at first to accept and adapt itself to everything it finds ready-made in the sphere of production in order to be able to produce material values.
Secondly, because, when improving one instrument of production or another, one element of the productive forces or another, men do not realize, do not understand or stop to reflect what social results these improvements will lead to, but only think of their everyday interests, of lightening their labor and of securing some direct and tangible advantage for themselves.
When, gradually and gropingly, certain members of primitive communal society passed from the use of stone tools to the use of iron tools, they, of course, did not know and did not stop to reflect what social results this innovation would lead to; they did not understand or realize that the change to metal tools meant a revolution in production, that it would in the long run lead to the slave system. They simply wanted to lighten their labor and secure an immediate and tangible advantage; their conscious activity was confined within the narrow bounds of this everyday personal interest.
When, in the period of the feudal system, the young bourgeoisie of Europe began to erect, alongside of the small guild workshops, large manufactories, and thus advanced the productive forces of society, it, of course, did not know and did not stop to reflect what social consequences this innovation would lead to; it did not realize or understand that this “small” innovation would lead to a regrouping of social forces which was to end in a revolution both against the power of kings, whose favors it so highly valued, and against the nobility, to whose ranks its foremost representatives not infrequently aspired. It simply wanted to lower the cost of producing goods, to throw larger quantities of goods on the markets of Asia and of recently discovered America, and to make bigger profits. Its conscious activity was confined within the narrow bounds of this commonplace practical aim.
When the Russian capitalists, in conjunction with foreign capitalists, energetically implanted modern large-scale machine industry in Russia, while leaving tsardom intact and turning the peasants over to the tender mercies of the landlords, they, of course, did not know and did not stop to reflect what social consequences this extensive growth of productive forces would lead to; they did not realize or understand that this big leap in the realm of the productive forces of society would lead to a regrouping of social forces that would enable the proletariat to effect a union with the peasantry and to bring about a victorious socialist revolution. They simply wanted to expand industrial production to the limit, to gain control of the huge home market, to become monopolists, and to squeeze as much profit as possible out of the national economy.
Their conscious activity did not extend beyond their commonplace, strictly practical interests.
Accordingly, Marx says:
In the social production of their life [that is. in the production of the material values necessary to the life of men — J. S.], men enter into definite relations that are indispensable and independent of their will, relations of production which correspond to a definite stage of development of their material productive forces. 
This, however, does not mean that changes in the relations of production, and the transition from old relations of production to new relations of production proceed smoothly, without conflicts, without upheavals. On the contrary such a transition usually takes place by means of the revolutionary overthrow of the old relations of production and the establishment of new relations of production. Up to a certain period the development of the productive forces and the changes in the realm of the relations of production proceed spontaneously independently of the will of men. But that is so only up to a certain moment, until the new and developing productive forces have reached a proper state of maturity. After the new productive forces have matured, the existing relations of production and their upholders — the ruling classes — become that “insuperable” obstacle which can only be removed by the conscious action of the new classes, by the forcible acts of these classes, by revolution. Here there stands out in bold relief the tremendous role of new social ideas, of new political institutions, of a new political power, whose mission it is to abolish by force the old relations of production. Out of the conflict between the new productive forces and the old relations of production, out of the new economic demands of society, there arise new social ideas; the new ideas organize and mobilize the masses; the masses become welded into a new political army, create a new revolutionary power, and make use of it to abolish by force the old system of relations of production, and to firmly establish the new system. The spontaneous process of development yields place to the conscious actions of men, peaceful development to violent upheaval, evolution to revolution.
The proletariat, during its contest with the bourgeoisie, is compelled, by the force of circumstances, to organize itself as a class … by means of a revolution, it makes itself the ruling class, and, as such, sweeps away by force the old conditions of production… 
The proletariat will use its political supremacy to wrest, by degrees, all capital from the bourgeoisie, to centralize all instruments of production in the hands of the State, i.e., of the proletariat organized as the ruling class; and to increase the total of productive forces as rapidly as possible. 
Force is the midwife of every old society pregnant with a new one. 
Here is the formulation — a formulation of genius — of the essence of historical materialism given by Marx in 1859 in his historic Preface to his famous book, A Contribution to the Critique of Political Economy:
In the social production of their life, men enter into definite relations that are indispensable and independent of their will, relations of production which correspond to a definite stage of development of their material productive forces. The sum total of these relations of production constitutes the economic structure of society, the real foundation, on which rises a legal and political superstructure and to which correspond definite forms of social consciousness. The mode of production of material life conditions the social, political and intellectual life process in general. It is not the consciousness of men that determines their being, but, on the contrary, their social being that determines their consciousness. At a certain stage of their development, the material productive forces of society come in conflict with the existing relations of production, or — what is but a legal expression for the same thing — with the property relations within which they have been at work hitherto. From forms of development of the productive forces these relations turn into their fetters. Then begins an epoch of social revolution. With the change of the economic foundation the entire immense superstructure is more or less rapidly transformed. In considering such transformations a distinction should always be made between the material transformation of the economic conditions of production, which can be determined with the precision of natural science, and the legal, political, religious, aesthetic or philosophic — in short, ideological forms in which men become conscious of this conflict and fight it out. Just as our opinion of an individual is not based on what he thinks of himself, so can we not judge of such a period of transformation by its own consciousness; on the contrary this consciousness must be explained rather from the contradictions of material life, from the existing conflict between the social productive forces and the relations of production. No social order ever perishes before all the productive forces for which there is room in it have developed; and new, higher relations of production never appear before the material conditions of their existence have matured in the womb of the old society itself. Therefore mankind always sets itself only such tasks as it can solve; since looking at the matter more closely, it will always be found that the task itself arises only when the material conditions for its solution already exist or are at least in the process of formation. 
Such is Marxist materialism as applied to social life, to the history of society.
Such are the principal features of dialectical and historical materialism.