Amartya Sen and Martha Nussbaum have suggested that normative political theory should take account of the quality of individuals' lives in terms of their functionings and of their capability to function. This article criticises their theory from a liberal point of view by showing its incompatibility with the Kantian maxim that individuals should be treated as ends in themselves. Three possible interpretations of Sen and Nussbaum's theory are examined: the theory might prescribe the government promotion of (a) capabilities and actual functionings as jointly necessary conditions for the good life, (b) capabilities and actual functionings as disjunctively sufficient conditions for the good life, or (c) only the capability to function well. On the first two interpretations, the theory has paternalist implications. The third interpretation improves on the first two, but still ignores that content-independent value that capabilities must have if individuals are to be treated as ends in themselves.