One of the oddities of Marxism is a general sense that capitalism always works, even or especially when it doesn’t work for workers. There’s a sense that everything has been accounted for. Marx isn’t quite guilty of this but his use of means of subsistence to calculate surplus value comes close.
The gist of Marx’s argument, rhetorically, is that surplus value is value produced above value equal to a worker’s means of subsistence. The presentation focuses on daily wages to emphasize that employers purchase a day of labor from workers and try to get as much labor out of workers in that period of time. What Marx wants to show is that surplus cannot be created through circulation. Hence the worker’s day of labor exchanges for its full value—its means of subsistence as historically determined—and capital tries to get more out of that the worker’s day through the extension of the day, which is limited by the hours in a day and the worker’s ability to recuperate, or through the intensification of work via co-operation and technological innovation.
Marx here seems to be working from a concept in Adam Smith: “A man must always live by his work, and his wages must at least be sufficient to maintain him” (book 1, chapter 8). For Smith, this sense of subsistence is bound up with a different mode of production—recall, Smith is writing not in the midst of developed capitalism but offering a dream of its possibility—and seems a version of “natural price” theory, which he uses elsewhere too (and in ways Marx will critique in subsequent volumes, if I recall correctly). We know both that commodities don’t have natural prices. We also know, through historical work, that commodities in the eighteenth century didn’t have natural prices so much as moral prices, prices which were set by feudal traditions and enforced by social action, as EP Thompson explains in his essay on the moral economy. Labor, to the extent it has a price during Smith’s time, would have a sort of moral price and be buoyed by other forms of production for its physical subsistence. Using it to analyze an economy premised on commodity exchange poses substantial difficulties.
Can we bracket this historical problem, though, and imagine means of subsistence as a concept that enters into the production of value? Perhaps. As a concept in Marx, it seems to bind the worker as a locus of physical and natural force to the larger natural metabolic process of life’s reproduction. In that sense, accounting for means of subsistence is necessary to imagine an economic organization that differs from capitalism because it distinguishes what is necessary from what is surplus. (This isn’t post-capitalism because it is still production for exchange, but that’s another problem.)
Capitalism as such doesn’t need the category of means of subsistence or care about it as a reality. This is why it is strange to see it built into the analysis of commodity production. Capitalism’s defining feature, its production of commodities for exchange to accumulate value, is indifferent to workers’ needs. What has been purchased as a day or an hour or a piece is all that matters. Hence Marx’s two categories of commodities in production already account for surplus value as simply the value produced in excess of the values consumed by production in terms of constant capital (e.g., means of production, raw materials, and so on) and variable capital (i.e., labor).
Why does this matter?
Means of subsistence suggests that capitalism cares about the ability of workers to reproduce their labor, that they must pay enough for workers to live. When one makes this central to the production of surplus value, then it seems that capitalism understands what is in its interest or its shared interests with workers. It doesn’t. Marx understands that, too. For the moment, I can only explain the retention of Smith’s concept of the means of subsistence something meant to look forward to an economy yet to come, an economy in which the despotism of production has shifted from individual capitalists and the impersonal market to planned political control.