In a time where many constitutions are as frequently amended as ordinary statutes, purposive constitutional interpretation is both commonplace and normatively justifiable. However, as recent Singaporean decisions demonstrate, a common purpose-related problem arising in statutory interpretation—the existence of conflicting purposes at different levels of abstraction—takes on an additional dimension of complexity in constitutional interpretation. While courts prefer specific over general purposes in statutory interpretation, on grounds that this upholds Parliament’s most precise intent, they hesitate to consistently do the same in constitutional interpretation. This article rationalizes this difference between statutory and constitutional interpretation, taking as its point of departure a unique dual function that all constitutions, even oft-amended constitutions, must discharge: the creation of efficient government and the legitimation of political systems. It develops a dual approach to constitutional interpretation in response to this dual function, which requires courts to prefer specific over general constitutional purposes in the event of conflict, except when those general purposes reflect norms which legitimate the constitution in society’s eyes. In doing so, this article develops an understanding of purposive constitutional interpretation that preserves a constitution’s essence, while accommodating the reality of frequent amendments.