Abstract: The concept of dialogue has become a central feature in contemporary thinking about constitutional review. Dialogues occur between courts and legislatures over the constitution’s meaning and implementation, making less clear the line between those institutions. This Essay links the idea of constitutional dialogue with the idea of constitutional duty, with the aim of illuminating modern constitutionalism more generally. It begins with a simple model of constitutional dialogue in which legislatures are the first movers, then switches the order so that courts are the first movers. Doing so brings out the connection between the ideas of dialogue and constitutional duty. Distinguishing among types of duty suggests that constitutions require not the maximization of any – or all – constitutional values, but joint maximization in which the constitutional system as a whole achieves as much as possible even though we can see that there is something more that the system could do to achieve any particular constitutional value. Finally, I suggest that joint maximization implies that only dialogic review is appropriate if we are interested in constitutional systems as a whole.