Legal responses to impaired capacity reflect different (and sometimes competing) values, with ongoing tension between empowerment and protection norms. These tensions are both inevitable and desirable; without them capacity law would be one-dimensional and conceptually inadequate. However, while normative underpinnings are important, concern with what law should be doing must not be allowed to distract from analysis of what law is doing. For this, we need to evaluate capacity law as a ‘social fact’. This article attempts to do this, tracing the evolution of capacity law and analyzing the circular dynamic whereby broader societal norms impact on developments within the legal system and law in turn impacts on developments outside of the legal system. In light of this analysis, it explores the ongoing role of capacity law as social and legal responses to impaired capacity continue to evolve.