Most American legal scholars have been slow to recognize the significance of John Rawls’s idea of public reason for law. This failure on their part is surprising, given the applicability of public reason to American constitutional theory, doctrine, and practice; it is also unfortunate constitutional theorists are not availing themselves of one of the most interesting ideas found in contemporary political philosophy literature. The main purpose of this contribution is to explain why American legal scholars must develop a conception of constitutional public reason (CPR) that suits the particulars of the American legal system. The other purpose is to address an objection to CPR, namely that it would be too shallow to provide sufficient normative orientation when judges must answer the most challenging constitutional questions. The objector alleges that even if judges were to endorse the same conception of CPR, it still might be indeterminate. As it turns out, CPR probably is no more prone to indeterminacy than any other theory of constitutional adjudication. Indeed, such reason may generate more determinacy when the pool of reasons that judges may draw from is considerably smaller.