  Some commentators, most notably Winkler, suppose that Berkeley retains this view of causality in the published works. The main difficulty with this interpretation is that Berkeley more than once purports to inspect our idea of body, and the sensory qualities included therein, and to conclude from that inspection that bodies are passive (DM 22, PHK 25). This procedure would make little sense if bodies, according to Berkeley, fail to be causes by definition, simply because they are not minds with  wills.[28]   What is needed is an explanation of what Berkeley means by activity, which he clearly equates with causal power. Winkler (1989, 130–1) supplies such an account, according to which activity means direction towards an end. But this is to identify efficient causation with final causation, a controversial move at best which Berkeley would be making without comment or argument. 