Erich Fromm 1961
A problem of the greatest importance is raised in the passage just quoted, that of human consciousness. The crucial statement is: "It is not consciousness of men that determines their being, but, on the contrary, their social being that determines their consciousness." Marx gave a fuller statement with regard to the problem of consciousness in German Ideology:
"The fact is, therefore, that definite individuals who are productively active in a definite way enter into these definite social and political relations. Empirical observations must in each separate instance bring out empirically, and without any mystification and speculation, the connection of the social and political structure with production. The social structure and the State are continually evolving out of the life-process of definite individuals, but of individuals, not as they may appear in their own or other people's imagination, but as they really are; i.e., as they are effective, produce materially, and are active under definite material limits, presuppositions and conditions independent of their will.
"The production of ideas, of conceptions, of consciousness, is at first directly interwoven with the material activity and the material intercourse of men, the language of real life. Conceiving, thinking, the mental intercourse of men, appear at this stage as the direct afflux from their material behavior. The same applies to mental production as expressed in the language of the politics, laws, morality, religion, metaphysics of a people. Men are the producers of their conceptions, ideas, etc. -real, active men, as they are conditioned by the definite development of their productive forces and of the intercourse corresponding to these, up to its furthest forms. Consciousness can never be anything else than conscious existence, and the existence of men in their actual lifeprocess. If in all ideology men and their circumstances appear upside down as in a camera obscura,[*] this phenomenon arises just as much from their historical lifeprocess as the inversion of objects on the retina does from their physical life-process." 
In the first place, it should be noted that Marx, like Spinoza and later Freud, believed that most of what men consciously think is "false" consciousness, is ideology and rationalization; that the true mainsprings of man's actions are unconscious to him. According to Freud, they are rooted in man's libidinal strivings; according to Marx, they are rooted in the whole social organization of man which directs his consciousness in certain directions. and blocks him from being aware of certain facts and experiences. 
Its is important to recognize that this theory does not pretend that ideas or ideals are not real or not potent. Marx speaks of awareness, not of ideals. It is exactly the blindness of man's conscious thought which prevents him from being aware of his true human needs, and of ideals which are rooted in them. Only if false consciousness is transformed into true consciousness, that is, only if we are aware of reality, rather than distorting it by rationalizations and fictions, can we also become aware of our real and true human needs.
It should also be noted that for Marx science itself and all powers inherent in man are part of the productive forces which interact with the forces of nature. Even as far as the influence of ideas on human evolution is concerned, Marx was by no means as oblivious to their power as the popular interpretation of his work makes it appear. His argument was not against ideas, but against ideas which were not rooted in the human and social reality, which were not, to use Hegel's term, "a real possibility." Most of all, he never forgot that not only do circumstances make man; man also makes circumstances. The following passage should make clear how erroneous it is to interpret Marx as if he, like many philosophers of the enlightenment and many sociologists of today, gave man a passive role in the historical process, as if he saw him as the passive object of circumstances:
"The materialistic doctrine [in contrast to Marx's view] concerning the changing of circumstances and education forgets that circumstances are changed by men and that the educator himself must be educated. This doctrine has therefore to divide society into two parts, one of which is superior to society [as a whole].
"The coincidence of the changing of circumstances and of human activity or self-changing can only be comprehended and rationally understood as revolutionary practice." 
The last concept, that of "revolutionary practice", leads us to one of the most disputed concepts in Marx's philosophy, that of force. First of all, it should be noted how peculiar it is that the Western democracies should feel such indignation about a theory claiming that society can be transformed by the forceful seizure of political power. The idea of political revolution by force is not at all a Marxist idea; it has been the idea of bourgeois society during the last three hundred years. Western democracy is the daughter of the great English, French and American revolutions; the Russian revolution of February, 1917, and the German revolution of 1918 were warmly greeted by the West, despite the fact that they used force. It is clear that indignation against the use of force, as it exists in the Western world today, depends on who uses force, and against whom. Every war is based on force; even democratic government is based on the principle of force, which permits the majority to use force against a minority, if it is necessary for the continuation of the status quo. Indignation against force is authentic only from a pacifist standpoint, which holds that force is either absolutely wrong, or that aside from the case of the most immediate defense its use never leads to a change for the better.
However, it is not sufficient to show that Marx's idea of forceful revolution (from which he excluded as possibilities England and the United States) was in the middle-class tradition; it must be emphasized that Marx's theory constituted an important improvement over the middle-class view, an improvement rooted in his whole theory of history.
Marx saw that political force cannot produce anything for which there has been no preparation in the social and political process. Hence that force, if at all necessary, can give, so to speak, only the last push to a development which has virtually already taken place, but it can never produce anything truly new. "Force," he said, "is the midwife of every old society pregnant with a new one."  It is exactly one of his great insights that Marx transcends the traditional middle-class concept -- he did not believe in the creative power of force, in the idea that political force of itself could create a new social order. For this reason, force, for Marx, could have at most only a transitory significance, never the role of a permanent element in the transformation of society.