“They are historical, but the product of rational imagination, rooted in an experience of what man is capable of and in a clear insight into the transitory character of previous and existing society.”

Human Nature and Social Theory (1969)
Context: What about the utopian thinkers of all ages, from the Prophets who had a vision of eternal peace, on through the Utopians of the Renaissance, etc.? Were they just dreamers? Or were they so deeply aware of new possibilities, of the changeability of social conditions, that they could visualize an entirely new form of social existence even though these new forms, as such, were not even potentially given in their own society? It is true that Marx wrote a great deal against utopian socialism, and so the term has a bad odor for many Marxists. But he is polemical against certain socialist schools which were, indeed, inferior to his system because of their lack of realism. In fact, I would say the less realistic basis for a vision of the uncrippled man and of a free society there is, the more is Utopia the only legitimate form of expressing hope. But they are not trans-historical as, for instance, is the Christian idea of the Last Judgment, etc. They are historical, but the product of rational imagination, rooted in an experience of what man is capable of and in a clear insight into the transitory character of previous and existing society.