Cartwright and Mill on Tendencies and Capacities

This paper examines the relation between Cartwright's concept of 'capacities' and Mill's concept of 'tendencies' and argues that they are not equivalent. Cartwright's concept of 'capacities' and her motivation to adopt it as a central notion in her philosophy of science are described. It is argued that the Millian concept of 'tendencies' is distinct because Mill restricts its use to a set of special cases. These are the cases in which causes combine 'mechanically'. Hence for Mill 'tendencies' do not merely describe the operation of causes, but also and perhaps even primarily how they combine. This does not hold of Cartwrightian capacities which are meant to have unlimited applicability. Mill also explicitly denies the realism of 'capacities' in a sense which overlaps with Cartwright's. Her attempt to derive empirist credentials for her notion of capacity from Mill is therefore unsuccessful.