“The previous regime — armed with its arrogant and intolerant ideology — reduced man to a force of production, and nature to a tool of production. In this it attacked both their very substance and their mutual relationship. It reduced gifted and autonomous people, skillfully working in their own country, to the nuts and bolts of some monstrously huge, noisy and stinking machine, whose real meaning was not clear to anyone.”

Statement (16 June 1970), quoted in The Times (17 June 1970), p. 4. This would be quoted back at Heath repeatedly during his premiership.
Leader of the Opposition

"Meat Makes the Planet Thirsty", in The New York Times (7 March 2014) https://www.nytimes.com/2014/03/08/opinion/meat-makes-the-planet-thirsty.html.

The Communist Manifesto, footnote (1888 edition)

“In these great times,” Harry Zohn, trans., In These Great Times (Montreal: 1976), pp. 73-74

1980s, GNU Manifesto (1985)

Political Anthropology: An Introduction (2003), p. 213

Anarchism: Its Philosophy and Ideal (1896)
Context: What economists call over-production is but a production that is above the purchasing power of the worker, who is reduced to poverty by Capital and State. Now, this sort of over-production remains fatally characteristic of the present capitalist production, because — Proudhon has already shown it — workers cannot buy with their salaries what they have produced and at the same time copiously nourish the swarm of idlers who live upon their work.
The very essence of the present economic system is, that the worker can never enjoy the well-being he has produced, and that the number of those who live at his expense will always augment. The more a country is advanced in industry, the more this number grows. Inevitably, industry is directed, and will have to be directed, not towards what is needed to satisfy the needs of all, but towards that which, at a given moment, brings in the greatest temporary profit to a few. Of necessity, the abundance of some will be based on the poverty of others, and the straitened circumstances of the greater number will have to be maintained at all costs, that there may be hands to sell themselves for a part only of that which they are capable of producing; without which, private accumulation of capital is impossible!
These characteristics of our economical system are its very essence. Without them, it cannot exist; for, who would sell his labor power for less than it is capable of bringing in, if he were not forced thereto by the threat of hunger?
And those essential traits of the system are also its most crushing condemnation.

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.

Grundrisse (1857-1858)
Source: Introduction, p. 10.