Approached in this way, the Leninist theory of organisation appears as a dialectical unity of three elements: a theory of the present relevance of revolution for the underdeveloped countries in the imperialist epoch (which was later expanded to apply to the entire world in the epoch of the general crisis of capitalism); a theory of the discontinuous and contradictory development of proletarian class consciousness and of its most important stages, which should be differentiated from one another; and a theory, of the essence of Marxist theory and its specific relationship to science on the one hand and to proletarian class struggle on the other.
Looking more closely, one discovers that these three theories form, so to speak, the "social foundation" of the Leninist concept of organisation, without which it would appear arbitrary, non-materialist and unscientific. The Leninist concept of the party is not the only possible one. It is, however, the only possible concept of the party which assigns to the vanguard party the historic role of leading a revolution which is considered, in an intermediate or long-range sense, to be inevitable. The Leninist concept of the party cannot be separated from a specific analysis of proletarian class consciousness, i.e., from the understanding that political class consciousness - as opposed to mere "trade union" or "craft" consciousness - grows neither spontaneously nor automatically out of the objective developments of the proletarian class struggle.  And the Leninist concept of the party is based upon the premise of a certain degree of autonomy of scientific analysis, and especially of Marxist theory. This theory, though conditioned by the unfolding of the proletarian class struggle and the first embryonic beginnings of the proletarian revolution, should not be seen as the mechanically inevitable product of the class struggle but as the result of a theoretical practice (or "theoretical production") which is able to link up and unite with the class struggle only through a prolonged struggle. The history of the world-wide socialist revolution in the twentieth century is the history of this prolonged process.
These three propositions actually represent a deepening of Marxism, i.e., either of themes that were only indicated but not elaborated upon by Marx and Engels, or of elements of Marxist theory which were scarcely noticed due to the delayed and interrupted publication of Marx’s writings in the years 1880-1905.  It therefore involves a further deepening of Marxist theory brought about because of gaps (and in part contradictions) in Marx’s analysis itself, or at least in the generally accepted interpretation of it in the first quarter century after Marx’s death.
What is peculiar about this deepening of Marx’s teaching is that, setting out from different places, it proceeds toward the same central point, namely, to a determination of the special character of the proletarian or socialist revolution.
In contrast to all previous revolutions - not only the bourgeois revolutions, whose laws of motion have been studied in great detail (in the first place by Marx and Engels themselves), but also those revolutions which have hitherto been far less subjected to a systematic, generalised analysis (such as the peasant revolutions and those of the urban petty bourgeoisie against feudalism; the uprisings of slaves and the revolts of clan societies against slaveholding society; the peasant revolutions that occurred as the old Asiatic mode of production periodically disintegrated, etc.) - the proletarian revolution of the twentieth century is distinguished by four particular features. These give it a specific character, but also, as Marx foresaw,  make it an especially difficult undertaking.
1. The proletarian revolution is the first successful revolution in the history of mankind to be carried out by the lowest social class. This class disposes of a potentially huge, but actually extremely limited, economic power and is by and large excluded from any share in the social wealth (as opposed to the mere possession of consumer goods which are continuously used up). Its situation is quite different from the bourgeoisie and the feudal nobility, who seized political power when they already held in their hands the actual economic power of society, as well as from the slaves, who were unable to carry through a successful revolution.
2.The proletarian revolution is the first revolution in the history of humanity aimed at a consciously planned overthrow of existing society, i.e., which does not seek to restore a previous state of affairs (as did the slave and peasant revolutions of the past), or simply to legalise a transfer of power already achieved on the economic field, but rather to bring into being a completely new process, one which has never before existed and which has been anticipated only as a "theory" or a "program." 
3. Just like every other social revolution in history, the proletarian revolution grows out of the internal class antagonisms and the class struggle they inevitably produce within the existing society. But while revolutions in the past could by and large be satisfied with pushing this class struggle forward until a culminating point was reached - because for them it was not a question of creating completely new and consciously planned social relations - the proletarian revolution can become a reality only if the proletarian class struggle culminates in a gigantic process, stretching out over years and decades. This process is one of systematically and consciously overturning all human relations, and of generalising first the independent activity of the proletariat, and later (on the threshold of the classless society) that of all members of society. While the triumph of the bourgeois revolution makes the bourgeoisie into a conservative class (which is still able to achieve revolutionary transformations in the technical and industrial fields, and which plays an objectively progressive role in history for a rather long period of time, but which pulls back from an active transformation of social life, since in that sphere its mounting collisions with the proletariat it exploits make it increasingly reactionary), the conquest of power by the proletariat is not the end but the beginning of the activity of the modern working class in revolutionising society. This activity can end only when it liquidates itself as a class, along with all other classes. 
4. In contrast to all previous social revolutions, which by and large have taken place within a national or an even more limited regional framework, the proletarian revolution is by nature international and can reach its conclusion only in the world-wide construction of a classless society. Although it certainly can achieve victory at first within a national framework alone, this victory will constantly be endangered and provisional so long as the class struggle on an international scale has not inflicted a decisive defeat upon capital. The proletarian revolution, then, is a world revolutionary process, which is carried out neither in a linear fashion nor with uniformity. The imperialist chain breaks first at its weakest links, and the discontinuous ebb and flow of the revolution occurs in conformity with the law of uneven and combined development. (This is true not only for the economy but also for the relationship of forces between classes; the two by no means automatically coincide,.) The Leninist theory of organisation takes into account all these peculiarities of the proletarian revolution. It takes into consideration the peculiarities of this revolution in light of, among other things, the peculiarities and contradictions in the formation of proletarian class consciousness. Above all, it expresses openly what Marx only intimated, and which his epigones scarcely understood at all, namely, that there can be neither an "automatic" overthrow of the capitalist social order nor a "spontaneous" or "organic" disintegration of this social order through the construction of a socialist one. Precisely because of the uniquely conscious character of the proletarian revolution, it requires not only a maturity of "objective" factors (a deepening social crisis which expresses the fact that the capitalist mode of production has fulfilled its historic mission), but also a maturity of so-called subjective factors (maturity of proletarian class consciousness and of its leadership). If these "subjective" factors are either not present, or are present to an insufficient extent, the proletarian revolution will not be victorious at that point, and from its very defeat will result the economic and social possibilities for a temporary consolidation of capitalism. 
The Leninist theory of organisation represents, then, broadly speaking, the deepening of Marxism, applied to the basic problems of the social superstructure (the state, class consciousness, ideology, the party). Together with the parallel contributions of Rosa Luxemburg and Trotsky (and, in a more limited sense of Lukacs and Gramsci), it constitutes the Marxist science of the subjective factor.