Here two important points must be emphasized. The first, which has been stated before This is the second half of Mao's seminal essay On Practice. The first half is dedicated to working through the relationship between theory and practice. It's was yesterday's reading unless we screw up the scheduling for the website.but should be repeated here, is the dependence of rational knowledge upon perceptual knowledge. Anyone who thinks that rational knowledge need not be derived from perceptual knowledge is an idealist. In the history of philosophy there is the "rationalist" school that admits the reality only of reason and not of experience, believing that reason alone is reliable while perceptual experience is not; this school errs by turning things upside down. The rational is reliable precisely because it has its source in sense perceptions, other wise it would be like water without a source, a tree without roots, subjective, self-engendered and unreliable. As to the sequence in the process of cognition, perceptual experience comes first; we stress the significance of social practice in the process of cognition precisely because social practice alone can give rise to human knowledge and it alone can start man on the acquisition of perceptual experience from the objective world. For a person who shuts his eyes, stops his ears and totally cuts himself off from the objective world there can be no such thing as knowledge. Knowledge begins with experience—this is the materialism of the theory of knowledge.

The second point is that knowledge needs to be deepened, that the perceptual stage of knowledge needs to be developed to the rational stage—this is the dialectics of the theory of knowledge. "In order to understand, it is necessary empirically to begin understanding, study, to rise from empiricism to the universal." (V. I. Lenin, "Conspectus of Hegel's The Science of Logic", Collected Works, Russ. ed., Moscow, 1958, Vol. XXXVIII, p. 197.) To think that knowledge can stop at the lower, perceptual stage and that perceptual knowledge alone is reliable while rational knowledge is not, would be to repeat the historical error of "empiricism". This theory errs in failing to understand that, although the data of perception reflect certain realities in the objective world (I am not speaking here of idealist empiricism which confines experience to so-called introspection), they are merely one-sided and superficial, reflecting things incompletely and not reflecting their essence. Fully to reflect a thing in its totality, to reflect its essence, to reflect its inherent laws, it is necessary through the exercise of thought to reconstruct the rich data of sense perception, discarding the dross and selecting the essential, eliminating the false and retaining the true, proceeding from the one to the other and from the outside to the inside, in order to form a system of concepts and theories—it is necessary to make a leap from perceptual to rational knowledge. Such reconstructed knowledge is not more empty or more unreliable; on the contrary, whatever has been scientifically reconstructed in the process of cognition, on the basis of practice, reflects objective reality, as Lenin said, more deeply, more truly, more fully. As against this, vulgar "practical men" respect experience but despise theory, and therefore cannot have a comprehensive view of an entire objective process, lack clear direction and long-range perspective, and are complacent over occasional successes and glimpses of the truth. If such persons direct a revolution, they will lead it up a blind alley.

Rational knowledge depends upon perceptual knowledge and perceptual knowledge remains to be developed into rational knowledge— this is the dialectical-materialist theory of knowledge. In philosophy, neither "rationalism" nor "empiricism" understands the historical or the dialectical nature of knowledge, and although each of these schools contains one aspect of the truth (here I am referring to materialist, not to idealist, rationalism and empiricism), both are wrong on the theory of knowledge as a whole. The dialectical-materialist movement of knowledge from the perceptual to the rational holds true for a minor process of cognition (for instance, knowing a single thing or task) as well as for a major process of cognition (for instance, knowing a whole society or a revolution).

But the movement of knowledge does not end here. If the dialectical-materialist movement of knowledge were to stop at rational knowledge, only half the problem would be dealt with. And as far as Marxist philosophy is concerned, only the less important half at that. Marxist philosophy holds that the most important problem does not lie in understanding the laws of the objective world and thus being able to explain it, but in applying the knowledge of these laws actively to change the world. From the Marxist viewpoint, theory is important, and its importance is fully expressed in Lenin's statement, "Without revolutionary theory there can be no revolutionary movement." Here, Mao quotes Lenin's What Is to be Done? But Marxism emphasizes the importance of theory precisely and only because it can guide action. If we have a correct theory but merely prate about it, pigeonhole it and do not put it into practice, then that theory, however good, is of no significance. Knowledge begins with practice, and theoretical knowledge is acquired through practice and must then return to practice. The active function of knowledge manifests itself not only in the active leap from perceptual to rational knowledge, but—and this is more important—it must manifest itself in the leap from rational knowledge to revolutionary practice. The knowledge which grasps the laws of the world, must be redirected to the practice of changing the world, must be applied anew in the practice of production, in the practice of revolutionary class struggle and revolutionary national struggle and in the practice of scientific experiment. This is the process of testing and developing theory, the continuation of the whole process of cognition. The problem of whether theory corresponds to objective reality is not, and cannot be, completely solved in the movement of knowledge from the perceptual to the rational, mentioned above. The only way to solve this problem completely is to redirect rational knowledge to social practice, apply theory to practice and see whether it can achieve the objectives one has in mind. Many theories of natural science are held to be true not only because they were so considered when natural scientists originated them, but because they have been verified in subsequent scientific practice. Similarly, Marxism-Leninism is held to be true not only because it was so considered when it was scientifically formulated by Marx, Engels, Lenin and Stalin but because it has been verified in the subsequent practice of revolutionary class struggle and revolutionary national struggle. Dialectical materialism is universally true because it is impossible for anyone to escape from its domain in his practice. The history of human knowledge tells us that the truth of many theories is incomplete and that this incompleteness is remedied through the test of practice. Many theories are erroneous and it is through the test of practice that their errors are corrected. That is why practice is the criterion of truth and why "the standpoint of life, of practice, should be first and fundamental in the theory of knowledge". Stalin has well said, "Theory becomes purposeless if it is not connected with revolutionary practice, just as practice gropes in the dark if its path is not illumined by revolutionary theory."

When we get to this point, is the movement of knowledge completed? Our answer is: it is and yet it is not. When men in society throw themselves into the practice of changing a certain objective process (whether natural or social) at a certain stage of its development, they can, as a result of the reflection of the objective process in their brains and the exercise of their subjective activity, advance their knowledge from the perceptual to the rational, and create ideas, theories, plans or programmes which correspond in general to the laws of that objective process. They then apply these ideas, theories, plans or programmes in practice in the same objective process. And if they can realize the aims they have in mind, that is, if in that same process of practice they can translate, or on the whole translate, those previously formulated ideas, theories, plans or programmes into fact, then the movement of knowledge may be considered completed with regard to this particular process. In the process of changing nature, take for example the fulfilment of an engineering plan, the verification of a scientific hypothesis, the manufacture of an implement or the reaping of a crop; or in the process of changing society, take for example the victory of a strike, victory in a war or the fulfilment of an educational plan. All these may be considered the realization of aims one has in mind. But generally speaking, whether in the practice of changing nature or of changing society, men's original ideas, theories, plans or programmes are seldom realized without any alteration.

This is because people engaged in changing reality are usually subject to numerous limitations; they are limited not only by existing scientific and technological conditions but also by the development of the objective process itself and the degree to which this process has become manifest (the aspects and the essence of the objective process have not yet been fully revealed). In such a situation, ideas, theories, plans or programmes are usually altered partially and sometimes even wholly, because of the discovery of unforeseen circumstances in the course of practice. That is to say, it does happen that the original ideas, theories, plans or programmes fail to correspond with reality either in whole or in part and are wholly or partially incorrect. In many instances, failures have to be repeated many times before errors In knowledge can be corrected and correspondence with the laws of the objective process achieved, and consequently before the subjective can be transformed into the objective, or in other words, before the anticipated results can be achieved in practice. But when that point is reached, no matter how, the movement of human knowledge regarding a certain objective process at a certain stage of its development may be considered completed.

However, so far as the progression of the process is concerned, the movement of human knowledge is not completed. Every process, whether in the realm of nature or of society, progresses and develops by reason of its internal contradiction and struggle, and the movement of human knowledge should also progress and develop along with it. As far as social movements are concerned, true revolutionary leaders must not only be good at correcting their ideas, theories, plans or programmes when errors are discovered, as has been indicated above; but when a certain objective process has already progressed and changed from one stage of development to another, they must also be good at making themselves and all their fellow-revolutionaries progress and change in their subjective knowledge along with it, that IS to say, they must ensure that the proposed new revolutionary tasks and new working programmes correspond to the new changes in the situation. In a revolutionary period the situation changes very rapidly; if the knowledge of revolutionaries does not change rapidly in accordance with the changed situation, they will be unable to lead the revolution to victory.

It often happens, however, that thinking lags behind reality; this is because man's cognition is limited by numerous social conditions. We are opposed to die-herds in the revolutionary ranks whose thinking fails to advance with changing objective circumstances and has manifested itself historically as Right opportunism. These people fail to see that the struggle of opposites has already pushed the objective process forward while their knowledge has stopped at the old stage. This is characteristic of the thinking of all die-herds. Their thinking is divorced from social practice, and they cannot march ahead to guide the chariot of society; they simply trail behind, grumbling that it goes too fast and trying to drag it back or turn it in the opposite direction.

We are also opposed to "Left" phrase-mongering. The thinking of "Leftists" outstrips a given stage of development of the objective process; some regard their fantasies as truth, while others strain to realize in the present an ideal which can only be realized in the future. They alienate themselves from the current practice of the majority of the people and from the realities of the day, and show themselves adventurist in their actions.

Idealism and mechanical materialism, opportunism and adventurism, are all characterized by the breach between the subjective and the objective, by the separation of knowledge from practice. The Marxist-Leninist theory of knowledge, characterized as it is by scientific social practice, cannot but resolutely oppose these wrong ideologies. Marxists recognize that in the absolute and general process of development of the universe, the development of each particular process is relative, and that hence, in the endless flow of absolute truth, man's knowledge of a particular process at any given stage of development is only relative truth. The sum total of innumerable relative truths constitutes absolute truth. The development of an objective process is full of contradictions and struggles, and so is the development of the movement of human knowledge. All the dialectical movements of the objective world can sooner or later be reflected in human knowledge. In social practice, the process of coming into being, developing and passing away is infinite, and so is the process of coming into being, developing and passing away in human knowledge. As man's practice which changes objective reality in accordance with given ideas, theories, plans or programmes, advances further and further, his knowledge of objective reality likewise becomes deeper and deeper. The movement of change in the world of objective reality is never-ending and so is man's cognition of truth through practice. Marxism-Leninism has in no way exhausted truth but ceaselessly opens up roads to the knowledge of truth in the course of practice. Our conclusion is the concrete, historical unity of the subjective and the objective, of theory and practice, of knowing ant doing, and we are opposed to all erroneous ideologies, whether "Left" or Right, which depart from concrete history.

In the present epoch of the development of society, the responsibility of correctly knowing and changing the world has been placed by history upon the shoulders of the proletariat and its party. This process, the practice of changing the world, which is determined in accordance with scientific knowledge, has already reached a historic moment in the world and in China, a great moment unprecedented in human history, that is, the moment for completely banishing darkness from the world and from China and for changing the world into a world of light such as never previously existed. The struggle of the proletariat and the revolutionary people to change the world comprises the fulfilment of the following tasks: to change the objective world and, at the same time, their own subjective world—to change their cognitive ability and change the relations between the subjective and the objective world. Such a change has already come about in one part of the globe, in the Soviet Union. There the people are pushing forward this process of change. The people of China and the rest of the world either are going through, or will go through, such a process. And the objective world which is to be changed also includes all the opponents of change, who, in order to be changed, must go through a stage of compulsion before they can enter the stage of voluntary, conscious change. The epoch of world communism will be reached when all mankind voluntarily and consciously changes itself and the world.

Discover the truth through practice, and again through practice verify and develop the truth. Start from perceptual knowledge and actively develop it into rational knowledge; then start from rational knowledge and actively guide revolutionary practice to change both the subjective and the objective world. Practice, knowledge, again practice, and again knowledge. This form repeats itself in endless cycles, and with each cycle the content of practice and knowledge rises to a higher level. Such is the whole of the dialectical-materialist theory of knowledge, and such is the dialectical-materialist theory of the unity of knowing and doing.