Fortunately, the real historical process proceeds quite differently. The change in social consciousness necessarily preceding the outbreak of revolution, as well as its subsequent evolution in the course of great struggles, is rooted in, and the expression of, socioeconomic processes that develop independently of individual consciousness. Moreover, the immense “leaps” in consciousness characteristic of a period of revolutionary struggle represent the long-postponed (and therefore explosive) realignment of social thought with external social reality.
This process was explained by Trotsky as follows:
The swift changes of mass views and moods in an epoch of revolution thus derive, not from the flexibility and mobility of man’s mind, but just the opposite, from its deep conservativism. The chronic lag of ideas and relations behind new objective conditions, right up to the moment when the latter crash over people in the form of a catastrophe, is what creates in a period of revolution that leaping movement of ideas and passions which seems to the police mind a mere result of the activities of “demagogues.” 
The experience of mass struggles changes people and their consciousness. Or, as Marx and Engels put it, when replying to the Brenners of the 1840s:
Both for the production on a mass scale of this communist consciousness and for the success of the cause itself, the alteration of men on a mass scale is necessary, an alteration which can only take place in a practical movement, a revolution; the revolution is necessary, therefore, not only because the ruling class cannot be overthrown in any other way, but also because the class overthrowing it can only in a revolution succeed in ridding itself of all the muck of ages and become fitted to found society anew. 
This justly celebrated passage appears in The German Ideology, written jointly by Marx and Engels in 1845. This work represented the first elaboration of the materialist conception of history, which explained man’s social consciousness on the basis of his social being, rather than man’s being on the basis of his consciousness. The forms of man’s thinking, they discovered, developed on an objective, material basis. “It is not consciousness that determines life, but life that determines consciousness.”  Their new conception of history and the development of consciousness “relies on expounding the real process of production—starting from the material production of life itself—and comprehending the form of intercourse connected with and created by this mode of production, i.e., civil society in its various stages, as the basis of all history...” 
The conception of social revolution as an objective product of real socioeconomic contradictions in the emerging capitalist system dealt a death-blow to all idealist interpretations of history. Moreover, the development of the working class itself as a revolutionary force within society, the “gravedigger” of capitalism, was an objective process. Its world-historical role was determined, in the most fundamental sense, not by its consciousness, but, rather, by its unique position in the capitalist mode of production. Answering what was to prove to be the most enduring objection to the conception of the proletariat as a revolutionary force—that the working class lacked revolutionary consciousness, that it did not want revolution, etc.—Marx and Engels replied in The Holy Family:
It is not a question of what this or that proletarian, or even the whole proletariat, at the moment regards as its aim. It is a question of what the proletariat is, and what, in accordance with this being, it will historically be compelled to do. Its aim and historical action is visibly and irrevocably foreshadowed in its own life situation as well as in the whole organisation of bourgeois society today. 
All Marxist discussion on the role of consciousness—a topic which, we should point out, in case you, Comrade Brenner, have not noticed, has been of considerable interest to the Trotskyist movement—must proceed from a correct understanding of its relationship to material processes of socioeconomic development. Plans for the building of a revolutionary party and the development of socialist consciousness would come to nothing if objective conditions did not permit the realization of these goals. The elaboration of the materialist conception of history marked a gigantic advance in man’s comprehension of his own social practice and consciousness. As Engels explained: “the final causes of all social changes and political revolutions are to be sought, not in men’s brains, not in man’s better insight into eternal truth and justice, but in changes in the modes of production and exchange. They are to be sought, not in the philosophy, but in the economics of each particular epoch.”  Even the emergence of a general “feeling” within broad sections of society that “things must change,” is a reflection in social consciousness of the archaic character of the prevailing political and economic system.
In Socialism: Utopian and Scientific Engels wrote:
The growing perception that existing social institutions are unreasonable and unjust, that reason has become unreason, and right wrong, is only proof that in the modes of production and exchange changes have silently taken place, with which the social order, adapted to earlier economic conditions, is no longer in keeping. From this it also follows that the means of getting rid of the incongruities that have been brought to light, must also be present, in a more or less developed condition, within the changed modes of production themselves. These means are not to be invented by deduction from fundamental principles, but are to be discovered in the stubborn facts of the existing system of production.
... The new productive forces have already outgrown the capitalistic mode of using them. And this conflict between productive forces and modes of production is not a conflict engendered in the mind of man, like that between original sin and divine justice. It exists, in fact, objectively, outside us, independently of the will and actions even of the men that have brought it on. Modern Socialism is nothing but the reflex, in thought, of this conflict in fact; its ideal reflection in the minds, first, of the class directly suffering under it, the working-class. 
Recognition that the emergence of the socialist movement has an objective foundation does not diminish the importance of the struggle to develop socialist consciousness. Indeed, the clarification of the objective basis of socialism is, itself, a critical component of the theoretical education of the working class. But a correct formulation of the socialist movement’s pedagogical tasks is possible only within the framework of an understanding that the contradictions of capitalism provide the principal and decisive impulse for the development of revolutionary consciousness.
The problem of socialist consciousness presents itself in one manner to those who recognize the latter as the ideal reflection of a real socioeconomic process, and in quite another to those who accept no such objective and necessary relationship between the economic foundations of capitalist society and the formation of social thought. For Marxists, the fight for socialist consciousness does not consist of convincing the broad mass of workers to conduct a struggle against capitalism. Rather, proceeding from a recognition of the inevitability of such struggles, which arise out of the objectively exploitative process of surplus-value extraction, intensified by the deepening economic and social crisis of the capitalist system, the Marxist movement strives to develop, within the advanced sections of the working class, a scientific understanding of history as a law-governed process, knowledge of the capitalist mode of production and the social relations to which it gives rise, and insight into the real nature of the present crisis and its world-historical implications. It is a matter of transforming an unconscious historical process into a conscious political movement, of anticipating and preparing for the consequences of the intensification of the world capitalist crisis, of laying bare the logic of events, and formulating, strategically and tactically, the appropriate political response.
For those, however, who see no basis for socialism in the objective conditions created by capitalism itself, who have been demoralized by the experience of defeats and setbacks, and who neither understand the nature of the capitalist crisis nor perceive the revolutionary potential of the working class, the problem of transforming consciousness is posed in essentially ideal, and even psychological, terms. Insofar as no real basis exists for socialist consciousness, the possibility for its development must be sought elsewhere. That is precisely why you, Comrades Brenner and Steiner, believe that “utopia is crucial to a revival of socialist culture.”
Leon Trotsky, The History of the Russian Revolution (London: Pluto Press, 1977), p. 18.
Marx-Engels Collected Works, Volume 5, (New York: International Publishers, 1976) pp. 52–53, [emphasis in the original].
ibid., p. 37.
ibid., p. 53.
Marx-Engels Collected Works, Volume 4, p. 37, [emphasis in the original].
Marx-Engels Collected Works, Volume 24, p. 306.
ibid., pp. 306–307.