Lenin, while pointing out weaknesses in the dialectical method adopted by Plekhanov, emphasised that the law of unity of opposites is the essence of dialectics. “Dialectics in proper sense is the study of contradiction in the very essence of objects.” Later on, Mao Zedong in his brilliant essay. 'On contradiction' discussed this essence of dialectics in detail, systematically and comprehensively. So, while dealing with dialectics, we will concentrate on this essence, i.e., unity and struggle of opposites or contradictions.

1. Contradictions, i.e. mutually opposite aspects exist universally and in all processes, whether in nature, society or in human thought. Struggle of these opposites is the very cause of development of these processes. Engels said, “Motion itself is a contradiction”. For example :

In mathematics : + and — ; X and ÷

In electricity : positive and negative

In social science : new and old, advanced and backward, slaves and slave-owners, serfs and feudal lords, workers and capitalists.

In war : Offense and defense, advance and retreat.

In human thought : reality and uptopia.

etc. etc., i.e. in every thing and process, contradiction, i.e. unity and struggle of opposites exists from beginning to end. Therefore, contrary to a metaphysician's approach of 'yea, yea; nay, nay', dialectical method demands that whenever we study any object, phenomenon or process, we study both the mutually opposite aspects and their interrelation inherent in that object or phenomenon, and not only one aspect. For example, when we study our nation, we should study mutually opposite classes and class-relations in our nation. In case of class struggle, we should study both legal and illegal struggles, political struggles and armed struggles and their mutual relationships.

Since struggle of opposites is inherent in every object and phenomenon and since development and motion is struggle of opposites, dialectical method demands that every thing should be viewed as in constant motion, always changing, always coming into being and passing away. Metaphysics refuses to do so. Take the case of non-aligned movement. Twenty years ago when this movement was born, it was directed against US imperialism because at that time it was US imperialism which was aggressively threatening the sovereignty and independence of nations. During these years the whole international scene changed and is constantly changing; the relative position of imperialist powers and developing countries has also changed. Non-aligned movement is turning more and more against Soviet imperialism. Metaphysicians regard this as a deviation from the concept of non-alignment because it was originally aimed at US imperialism and it should remain so even today. But according to dialectics this change is natural corresponding to the change in circumstances.

Moreover, dialectics teaches us to analyse any development basically due to contradiction inherent in it. So if workers rebel in Poland, the basic cause can never be “foreign hands”, but it is basically the result of contradictions inherent in Polish society itself. Hence, the 'theory of external factors' betrays a metaphysical mode of thought.

2. It is true that contradiction is present in the process of development of all things, but it does not mean that the same contradiction permeates the process of development of each thing. If it be so then in the world only one type of thing would have remained, i.e. only one form of motion of matter. But we see different type of matters and processes. Each type of matter and process has its own particular contradiction, i.e. particular set of opposites, which differentiates it with other things and processes. Wheat and barley have different forms of contradictions inherent in them which explains for their difference in forms. Every branch of knowledge contains within itself its own particular contradiction which differentiates it from another branch of knowledge. For example : positive and negative numbers in mathematics, action and reaction in mechanics, positive and negative electricity, forces of production and relations of production, opposite classes in social science, idealism and materialism in philosophy etc. Each social system has its own particular contradiction. In salve society, between slaves and slave owners, in feudal society between serfs and landlords, in capitalists society between workers end capitalists. So contrary to metaphysics, dialectical method demands that we should not only study contradictions generally, but what is especially important, we should study this particular contradiction in any object and phenomenon, be it natural or social. When we study our nation, we should not only study this general contradiction but also the particular contradiction which differentiates it from other nations. We should not only study class struggles in general but also the particularity of class struggle in our country and we should not only study mass movements in general but also the particularity of each and every mass movement.

3. Recognition of particular contradiction does not mean that in every entity there is only one contradiction i.e., one particular contradiction. Dialectics teaches us that there may remain many contradictions in a single entity. As the number of contradictions increases in any entity, it develops from simple to complex. So, if in any given entity or process, there are more than one contradictions, there is necessarily one principal contradiction whose existence and development determines or influences the existence and development of other contradictions. Through solving this principal contradiction, that matter, social system or process enters a new phase of development. So dialectical method demands that when studying any object or phenomenon, we should discover principal contradiction and solve it. Without this we will be lost in a fog. (On the questions of determining principal contradiction in society we shall discuss it in our chapter 'Historical Materialism.')

4. To solve a principal contradiction, it is necessary to study both of its mutually opposite aspects. According to dialectics, in any contradiction, i.e. in any pair of two mutually opposite aspects one is principal aspect and the other is secondary. The nature of a thing is determined mainly by the principal aspect of a contradiction. In any person there are both good and bad aspects. If good aspect is principal one, we call that person good. Despite the principal (dominant) position of one aspect the existence of secondary aspect shows the continuity of struggle, of motion. Under certain conditions, the two aspects of a contradiction interchange their place i.e., principal aspect becomes secondary and the secondary becomes principal one. Good man turns into bad one, brave into coward and a person coming from exploited class becomes exploiter. Here, the analysis of overall changing situation is necessary. It means not only the study of these two aspects of any contradiction separately, but also the study of its inter-relations with other contradictions, analysis of changes occurring in these interrelations and their resultant influence on the position of these two aspects. In other words, objects and phenomena should be studied in the light of their changing interrelations with other objects and phenomena and the resultant effect on their own position. Hence to understand the inter change of place by principal and secondary aspects of any contradiction the first thing is to study the objective overall situation.

So under certain conditions, the change occurs in the relative position change slowly, quantitatively. For example, in a person the proportion of good and bad aspects changes from 70 : 30, to 60 : 40. At this stage, the nature of that person does change but it is not felt apparently, i.e. still we call him good because good aspect is still principal. But in the process of development, the portion of good aspect undergoes a drastic change say, it becomes 30 : 70. Now quantitative change has turned into a qualitative change i.e. principal and secondary aspects have changed their place—secondary aspect has become principal and vice versa. The nature of man has also changed—from good it has now turned into bad one. This qualitative change is also called leap in the process of development. Metaphysics denies such leaps in the process of development. For it, all changes are mechanical, quantitative ones.

Hence, contrary to metaphysics, dialectical method demands that we should not only study general, particular and principal contradictions, but we should also investigate the two aspects of a contradiction. We should always analyse overall changing situation and its subsequent impact on these two aspects of a contradiction whether quantitative or qualitative. Therefore, a revolutionary party always analyses changing national and international situation and its impact on the two aspects of the contradiction (people versus ruling classes) and through this process always enriches or changes its line, policies or slogans. (By the way, it should be remembered that changes in two aspects of a contradiction again influence the overall situation).

In class struggle, turning of ruling classes into ruled ones and ruled classes into ruling ones is a qualitative change. But this is a protracted process and in the meantime quantitative changes in the relative position of rulers and ruled always occur. In the process of class struggle, autocratic political forces emerge from among ruling classes and the struggle of various sections of the masses turns against these forces. Now if revolutionary forces do not take into account this quantitative change in the relative position of two opposing aspects, do not enrich their policies and slogans to concentrate their struggle against this autocratic force and build up a broad-based people's united front, then they will not be able to lead the class struggle through to the end, i,e, they will not be able to facilitate the qualitative change. After Second world war, in Chinese revolution Mao Zedong also concentrated his struggle against four houses—Chiang Kaishek, T V Sung, H H Khung and Chen Lifu and hardliners among Kuomintang and forged a broad-based united front with all the peace-loving democratic forces.

So, dogmatism is completely antilogous to dialectical method.

5. Interchangeability of opposite aspects in a contradiction does not mean that the same principal and secondary aspects always interchange. It will mean that development of any object revolves around the same circle. According to dialectics, during struggle of opposites in any object, these opposing aspects transform themselves when the secondary aspect becomes principal one, a new object comes into being and with it comes new type of contradictions, i.e. new set of opposites. The old process ends and new one begins. The new process contains new contradictions and begins its own history of development of contradictions. Resolution of every contradiction is at the same time starting point of a new type of contradiction. For example, take the case of organising peasants. In this process, there are, various opposing aspects—on the one hand, peasants' desire for organisation to get their right on land and on the other landlords' resistance, unorganised life of peasants and the necessity for organisation etc. So the process of organising the unorganised peasantry is a protracted process during which, through resisting attacks of landlords and through overcoming their own anarchist ideas during struggle, peasants organise themselves and become owners of the land they uptil now used to till. Along with it, landlord class is exterminated. Thus in this process opposing aspects change their place—unorganised peasants get organised, landless peasants become landholders ruled peasants become rulers and on the other hand, ruler landlord class turns into ruled. Qualitative change occurs in the rural society. A new society emerges. Though in this new society, old contradictions, i.e. old sets of opposites remain upto a certain period, they gradually disappear. And with new society come new contradictions — contradictions between organised landholder peasants and backward condition of agriculture, ever-increasing demands of peasantry and scarcity of consumer goods and in new conditions, among peasants themselves, contradictions between new and old, between advanced and backward sections.

In class struggle, political struggle and armed struggle— these two aspects also change their place, sometimes the former becomes principal aspect and at other times the latter. But in this process of interchange, both the aspects transform themselves too. Hence the interchange also does not occur in a circular, repetitive manner. Every time these two aspects come before us with new characteristics. So, mechanical repetition of old type of armed struggle or old type of political struggle only betrays metaphysical mode of thought.

6. If during the process of development, old contradictions pass away and new contradictions emerge, if so many types of contradictions exist in Nature and society, can we solve all these contradictions in the same manner? certainly not. According to dialectics, qualitatively different type of contradictions can only be solved by qualitatively different methods. For instance, the contradiction between the proletariat and the bourgeoisie is resolved by the method of socialist revolution, the contradiction between great masses of the people and the feudal system is resolved by the method of democratic revolution, the contradiction between colonies and imperialism is resolved by the method of national revolutionary war, the contradiction between society and nature is resolved by the method of developing the productive forces etc. etc. So, to guide the process of social development, not only it is necessary to know various types of contradictions but it is also necessary to chalk out different methods to solve different types of contradictions—contradictions between people and enemy, contradictions among democratic forces, contradictions between proletarian vanguards and democratic forces etc. etc.

Here, we have discussed some of the salient features of dialectical method. In a nut-shell, as Lenin said, “The splitting in two of a single whole and the cognition of its contradictory parts is the essence of dialectics.” So dialectical method is also expressed as “one divides into two.” This method is just opposite to the metaphysical method of “yea, yea; no, no”, either this or that. Due to this method, metaphysics is unable to explain so many changes occurring in our world, and to lead a revolutionary movement.

But in the camp of dialecticians, some do not give emphasis on “unity and struggle of opposites”. Precisely due to this Lenin emphasised on it while writing on Plekhanov's method. He also said, “In brief, dialectics can be defined as the unity of opposites. This grasps the karnel of dialectics, but it requires explanations and development.” So Lenin emphsised not only on this doctrine but also emphasised on the necessity of further explaining and developing this doctrine. Thus Lenin approached this doctrine not metaphysically, but dialectically and therefore he emphasised the necessity to further explain and develop it. And this is precisely what Mao Zedong did in his “On Contradiction.” But naturally, the problem of explaining and developing this doctrine in our changing world did not end there.

Moreover, even among those who abide by the doctrine of unity and struggle of opposites, some emphasise on unity of opposites in such a manner that it turns into its opposite i.e. eclecticism. On unity and struggle of opposites, Mao Zedong says, “There are two states of motion in all things, that of relative rest and of that conspicuous change. Both are caused by the struggle between the two contradictory elements contained in a thing. When the thing is in the first state of motion, it is undergoing only quantitative and not qualitative change and consequently presents the outward appearance of being at rest. When the thing is in the second state of motion, the quantitative change of the first state has already reached a culminating point and gives rise to the dissolution of the thing as an entity and thereupon a qualitative change ensues, hence the appearance of a conspicuous change. Such unity, solidarity, combination, harmony, balance, stalemate, deadlock, rest, constancy, equilibrium, solidity, attraction etc., as we see in daily life, are all appearances of things in the state of quantitative change. On the other hand, the dissolution of unity, i.e. the destruction of this solidarity, combination, harmony, balance, stalemate deadlock, rest, constancy, equilibrium, solidity and attraction, and the change of each into its opposite are all appearances of things in state of qualitative change, the transformation of one process into another. Things constantly transforming themselves from the first into the second state of motion, the struggle of opposites goes on in both states but the contradiction is resolved through the second state. That is why we say that unity of opposites is conditional, temporary and relative, while the struggle of mutually exclusive opposites is absolute.” Eclectics only know of first state of motion and therefore they are unable to resolve any contradiction.