Marx''s account of capitalist exploitation is undermined by inter-related confusions surrounding the notion of labour power. These confusions relate to [i] what labour power is, [ii] what happens to labour power in the labour market, and [iii] what the epistemic status of labour power is (the issue of appearance and reality). The central theses of the paper are [a] that property ownership is the wrong model for understanding the exploitation of labour, and [b] that the concept of exploitation is linked more fruitfully to a conception of distributive injustice than to Marx''s theory of surplus value.