In recent political-economic theories of nature', Mill and Marx/Engels form important reference points. Ecological economists see Mill's stationary state' as seminal, while Marxists have brought capitalism back in' to debates on growth and climate change, sparking a Marxological renaissance that has overturned our understanding of Marx/Engels' opus. This article explores aspects of Mill's and Marx/Engels' work and contemporary reception. It identifies a resemblance between their historical dialectics. Marx's communism is driven by logics of agency' and structure' (including the tendency of profit rates to fall'). In Mill's dialectic a thesis', material progress, calls forth its antithesis', diminishing returns. The inevitable Aufhebung' is a stationary state of wealth and population; Mill mentions countervailing tendencies but fails to consider their capacity to postpone utopia's arrival. Today, Mill's schema lives on in ecological economics, shorn of determinism but with its market advocacy intact. It appears to contrast with the productive forces expansion' espoused by Marx/Engels. They stand accused of Promethean arrogance', ignoring natural limits' and gambling on abundance'. But I find these criticisms to be ill-judged, and propose an alternative reading, arguing that their work contains a critique of the growth paradigm', and that their cornucopian' ends do not sanction Promethean' means.