“The worker can create nothing without nature, without the sensuous external world. It is the material on which his labor is realized, in which it is active, from which, and by means of which it produces. But just as nature provides labor with [the] means of life in the sense that labor cannot live without objects on
which to operate, on the other hand, it also provides the means of life in the more restricted sense, i.e., the means for the physical subsistence of the worker himself”