Amartya Sen has made a major contribution to the theory of social justice, and of gender justice, by arguing that capabilities are the relevant space of comparison when justice-related issues are considered. This article supports Sen's idea, arguing that capabilities supply guidance superior to that of utility and resources (the view's familiar opponents), but also to that of the social contract tradition, and at least some accounts of human rights. But I argue that capabilities can help us to construct a normative conception of social justice, with critical potential for gender issues, only if we specify a definite set of capabilities as the most important ones to protect. Sen's "perspective of freedom" is too vague. Some freedoms limit others; some freedoms are important, some trivial, some good, and some positively bad. Before the approach can offer a valuable normative gender perspective, we must make commitments about substance.