John Roemer's comment (1992) succinctly summarizes the logical structure of his own theory of capitalist exploitation, but misunderstands the main points of our critique. He reduces his argument to two propositions. The first is an “empirical proposition”about the “root causes of exploitation”: X + Y →Z, where X is the existence of differential ownership of means of production (DOPA), Y is coercion in the labor process, and Z is the capitalist class structure and exploitation. The second is the strictly theoretical proposition X + not-Y -”Z, the truth of which he demonstrates, given most of the assumptions of a Walrasian economic model. He concludes that these two propositions, taken together, demonstrate the primacy of DOPA in explaining capitalist class relations. This much is true – subject to the various limitations we have indicated in our article – but only within the restricted confines of a Walrasian framework. This purely theoretical conclusion has no force as an empirical conclusion: this is the point at which Roemer's interpretation goes awry. For obviously, DOPA is a crucial element of empirical reality. But because Roemer's Walrasian framework precludes other equally crucial elements of empirical reality (which are also conceptually central to Marxian discourse), an irreducible distance remains therein between the theoretical and the empirical.