Certainly, Marx acknowledged a “historical and moral element” in the constitution of wages, as well as victories for the “political economy of the working class such as the ten-hour day.” Likewise, the level of “necessary needs,” as Michael Lebowitz rightly insists, is “the product of class struggle,” not a fixed physiological minimum; and, in turn, the qualitative growth of the “standard of necessity” helps drive the economic class struggle forward.109 But Marx believed that such gains and the new needs they created would be cyclically eroded by crises, whose tendency was to become more general and destructive over time.