{W}ithin bourgeois society, the society that rests on exchange value, there arise relations of circulation as well as of production which are so many mines to explode it. (A mass of antithetical forms of the social unity, whose antithetical character can never be abolished through quiet metamorphosis. On the other hand, if we did not find concealed in society as it is the material conditions of production and the corresponding relations of exchange prerequisite for a classless society, then all attempts to explode it would be quixotic.)
—Marx, Grundrisse
Hat Tip to Harrison Fluss.
Source: http://www.marxists.org/archive/marx/works/1857/grundrisse/ch03.htm