How we cite our quotes: (Chapter.Section.Paragraph) or (Chapter.Paragraph)
Quote #4
One thing, however, is clear: nature does not produce on the one hand owners of money or commodities, and on the other hand men possessing nothing but their own labour-power. This relation has no basis in natural history, nor does it have a social basis common to all periods of human history. It is clearly the result of a past historical development, the product of many economic revolutions, of the extinction of a whole series of older formations of social production. (6.7)
Marx is emphasizing once again that the division between the rich and the working class isn't natural. In about the 16th century, the capitalists, a small segment of society that made trading assets for surplus-value their life-work began to gain power. They eventually seized political power away from the landed aristocracy in Europe and expanded markets across the globe. But we're so used to capitalism today that we imagine it has always been here.
Quote #5
Given the existence of the individual, the production of labour-power consists in his production of himself or his maintenance. (6.11)
On the other hand, labor-power (the capacity to work) and necessary labor (the amount of time it takes to produce means of sustenance such as food, clothing and shelter) are natural to all life, to any individual's existence. No matter the society, people have to work to maintain themselves and keep themselves alive.
Quote #6
Labour is, first of all, a process between man and nature, a process by which man, through his own actions, mediates, regulates and controls the metabolism between himself and nature. He confronts the materials of nature as a force of nature. He sets in motion the natural forces which belong to his own body, his arms, legs, head and hands, in order to appropriate the materials of nature in a form adapted to his own needs. Through this movement he acts upon external nature and changes it, and in this way he simultaneously changes his own nature. He develops the potentialities slumbering within nature, and subjects the play of its forces to his own sovereign power. (7.1.2)
This passage shows Marx using dialectical reasoning to discuss people's relationship with nature. The dialectic is that people change external nature through work, and at the same time, nature changes them. In Marx, it's not linear cause-and-effect: not that nature causes people to change or that people cause nature to change. Instead, both change together. So Marx wouldn't partition off environmental concerns from other political or activist issues; he'd say that all human work is interaction with nature.